-A123 731 LONG-TERM MODIFICATIONS OF PERENNIALLY FROZEN SEDIMENT i/i \AND TERRAIN AT EAS..(U) COLD REGIONS RESEARCH ANDENGINEERING LAB HANOVER NH D E LAWSON NOV 82

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US Army CorpsREPORT 82-36 of EngineersCold Regions Research &Engineering Laboratory

Long-term modifications of perenniallyfrozen sediment and terrain at East Oumalik,northern Alaska

c77

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Cover: Th'ermokarst topography of the dis-turbed East .qmqlik upland drill sitein 1980 D ppltform was locatedOn tO,!gw.QqWKs rface at left center.Linear deprePaions lie where timberbeams were lodated. Depressionspartialt ?(llefd k..th snow mark formerbulldozbd-roads. Receiving and sup-ply sto-"46,0tfi'drm on steel barrelswas located in "oreground. (Photo-graph by D. Lawton.)

4i

I

CRREL Report 82-36November 1982

Long-term modifications of perenniallyfrozen sediment and terrain at East Oumalik,northern Alaska

* Daniel E. Lawson

ACO~SIoU ror

IDTIC TAB E

iyatlablIty Codes

Prepared forU.S. GEOLOGICAL SURVEY

4 Approved for public release; distribution unlimited.

UnclassifiedSECURITY CLASSIFICATION OF THIS PAGE (nen Data Entered)

REPORT DOCUMENTATION PAGE READ INSTRUCTIONSREPORT__ DOCUMENTATION _PAGE_ BEFORE COMPLETING FORM

1. REPORT NUMBER 12. GOVT ACCESSION NO. 3. RECIPIENT'S CATALOG NUMBER

CRREL Report 82-36 ,? 4-,;? . 7-( _

4. TITLE (and Subtitle) S. TYPE OF REPORT & PERIOD COVERED

LONG-TERM MODIFICATIONS OF PERENNIALLYFROZEN SEDIMENT AND TERRAIN ATEAST OUMALIK, NORTHERN ALASKA 6. PERFORMING ORG. REPORT NUMBER

7. AUTHOR(q) S. CONTRACT OR GRANT NUMBER(e)

Daniel E. Lawson

9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT, PROJECT, TASKAREA & WORK UNIT NUMBERS

U.S. Army Cold Regions Research and Engineering LaboratoryHanover, New Hampshire 03755

I1. CONTROLLING OFFICE NAME AND ADDRESS 12. REPORT DATE

U.S. Geological Survey November 1982

Reston, Virginia 22070 13. NUMBER OF PAGES

4214. MONITORING AGENCY NAME & ADDRESS(If different from Controlling Oice) IS. SECURITY CLASS. (of this report)

Unclassified

Isa. DECL ASSI FICATION/DOWNGRADINGSCHEDULE

16. DISTRIBUTION STATEMENT (of this Report)

Approved for public release; distribution unlimited.

17. DISTRIBUTION STATEMENT (of the abstract entered in Block 20, If different from Report)

IS. SUPPLEMENTARY NOTES

4

19. KEY WORDS (Continue on reverse side if neceseary end Identify by block number)

Alaska PermafrostEnvironmental impact SoilsErosion Thermal degradationGround ice Thermokarst

4 Ice wedges Tundra20. ABSTlRACT rcmitae a reverse af if nmeeaay and Identify by block number)

Camp construction and drilling activities in 1950 at the East Oumalik drill site in northern Alaska caused extensivedegradation of ice-rich, perennially frozen silt and irreversible modification of the upland terrain. In a study of thelong-term degradational effects at this site, the near-surface geology was defined by o 1ling and coring 76 holes (maxi-mum depth of 34 m) in disturbed and undisturbed areas and by laboratory analyses of these cores. Terrain distur-bances, including bulldozed roads and excavations, camp structures and off-road vehicle trails, were found to haveseverely disrupted the site's thermal regime. This led to a thickening of the active layer, melting of the ground ice,thaw subsidence and thaw consolidation of the sediments. Slumps, sediment gravity flows and collapse of materialson slopes bounding thaw depressions expanded the degradation laterally, with thermal and hydraulic erosion removing

DD ,o"" 1473 EDIToI OF i NOV 65 is OeSOLETE ECUR ITAF UnclassifiedSECURITY CLASSIFICATION OF TH"IS PAGE (WhR~en Data Entered)

UnclassifiedSECURITY CLASSIFICATION OF THIS PAGE(Whm Data Entered)

20. Abstract (cont'd).

material as the depressions widened and deepened with time. Degradational processes became less active after thawed

sediments thickened sufficiently to slow the increase in the depth of thaw and permit slope stabilization. The site'sterrain is now irregular and hummocky with numerous depressions. Seasonal thaw depths are deeper in disturbed areas

than in undisturbed areas and reflect the new moisture conditions and morphology. The severity of disturbance is muchgreater at East Oumalik than at another old drill site, Fish Creek. The difference results primarily from differences in the

*physical properties of the sediments, including the quantity and distribution of ground ice. In areas similar to EastOumalik, the removal or severe compaction of the vegetative mat would cause similar adverse physical changes to takeplace over two to three decades and should therefore be avoided.

Unclassified

SECURITY CLASSIFICATION OF THIS PAGE(When Data Entered)

PREFACE

This report was prepared by Dr. Daniel E. Lawson, Research Physical Scientist,of the Earth Sciences Branch, Research Division, U.S. Army Cold Regions Researchand Engineering Laboratory. It is based upon field research in northern Alaska andlaboratory studies in Hanover that were conducted from 1977 to 1981.

This research was funded by the U.S. Geological Survey under the National Pe-

troleum Reserve-Alaska (NPRA) program. The author thanks Dr. Max C. Brewer,Dr. John Haugh and James Stout of the Office of the NPRA for their assistance andenthusiastic support of this project, and the many personnel at Camp Lonely in theNPRA who provided continuous logistical support. The author thanks DanielCrowner, William Davies and Richard Mead who assisted in the field, Dr. JerryBrown, Dr. L. David Carter, Frederick Crory, Dr. K.R. Everett, Oscar J. Ferrians,Lawrence Gatto and Paul Sellmann for their helpful critical reviews of this manu-script, Eleanor Huke for drafting the figures and Edmund Wright for editing thereport.

The author especially thanks Bruce Brockett for his enthusiastic assistance in thefield, his perseverance in operating the drill rig and obtaining core of the permafrost

under sometimes very trying conditions, and his discussions of the research.The contents of this report are not to be used for advertising or promotional pur-

poses. Citation of brand names does not constitute an official endorsement or ap-proval of the use of such commercial products.

iii

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CONTENTS

PageA b s tra c t .............. . . .. ... ............ ..............P re fa c e .................. .......... ............. .........iiiS u m m a ry . ...... .... ........................ ..... ... v iIn tro d u c tio n ................. ...... .................. . 1M e tho d o lo gy ... ........... .... . ........................ . 2

G eo lo g ic se ttin g ........ ..... ................. ............... 3Camp construction and occupation 5.............. ............... 5Types of d isturbance ..... ................................... 8

Degradational processes and the effective area of impact ............. 11A real effects of disturbance ...................................... 16

T o p o g ra p hy ..... .............. ..... ..... ..... ........... 1 7

Groundwater, surface water and drainage ......................... 17Sediment properties and near-surface stratigraphy ................. 17

Su rfic ia l p ro cesses ... .... .................................... 21D epth of thaw ................................... 22

Com parison to Fish C reek ........................................ 24D iscussion and conclusions .......................... .......... .. 30L ite ra tu re c ite d ............................... .................. 30

ILLUSTRATIONS

Figure1. Location of the East Oumalik, Fish Creek and Oumalik drill sites in

th e N P R A ......................... .......... ......... 22. Topographic map of the region surrounding the East Oumalik drill

s it e ........... ....................................... 33. Undisturbed upland surface looking east of the former drill site in

19 8 0 ......... ............... .. .. ............ 4

4. Aerial photograph of the East Oumalik drill site on 6 September 1948prior to occupatio n ..................................... 5

5. Equipment in use in 1949 at the Oumalik drill site before tear-downand transport to the East Oumalik site in 1950 ............... 6

6. Locations of primary structures and roads at the East Oumalik drillsite determined by observations of the site in 1978 .......... 7

7. Lightly disturbed areas ......... . ....... .. . 98. Subsided area traversed by camp vehicles on northeast area of site.. 109. Former bulldozed trail at northeast corner of former site .......... 10

10. Former drainage ditch on north margin of site .................... 1111. Thermal and physical modifications of ice-rich permafrost terrain at

E a st O u m alik ..... ... .............. .. .................. 1 212. Schematic process-response flow chart illustrating the common se-

quences of processes that caused the modification of the EastO u m a lik site ....... ........ . .. . ........................ 1 3

iv

r r .. - , ° , _ , , _- . . - , r - -

Figure Page13. Stratigraphic cross sections of undisturbed and disturbed upland

sedim ents at East O um alik ............................... 1414. Representative frequency curves and cumulative curves of grain size

distribution of samples from upland silt at East Oumalik ...... 15

15. Water content of frozen undisturbed silts compared to their liquid-ity in d e x . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 6

16. Mosaic of aerial photographs of the East Oumalik drill site in 1978. 18

17. Topographic map and cross sections of the East Oumalik drill site in1 9 7 8 . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 9

18. Comparison of properties of typical stratigraphic sections of undis-turbed upland and thaw depression in disturbed upland ....... 20

19. Stratigraphic profile observed above partly melted ice wedge at EastO u m a lik . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1

20. Isopach lines of active layer thickness on 26 July 1978 ..... 23

21. Comparison of active layer thickness in July 1978 in disturbed andundisturbed parts of upland and surrounding stream valleys... 24

22. Aerial photograph of the Fish Creek dirll site in 1977 .............. 25

23. Representative frequency curves and cumulative curves of grain sizedistribution in samples of eolian sand at Fish Creek ......... 26

24. Stratigraphic cross sections of undisturbed and disturbed areas atFish Creek .............................. ........ 27

25. Aerial photograph of area around concrete drill pad at Fish Creek site 28

TABLES

Table1. Classification of disturbance by activities and their initial modifica-

tion of vegetation, soils and sediment ..................... 82. General comparison of physical modifications of terrain at East

O um alik and Fish Creek drill sites .......................... 273. Selected properties of near-surface sediment from undisturbed and

disturbed locations at the East Oumalik and Fish Creek drill sites 28

v

SUMMARY

Camp construction and drilling activities that took place during approximately10 months in 1950/1951 at the East Oumalik drill site in northern Alaska initiatedextensive degradation of ice-rich permafrost and irreversible modification of

about 3.5 km2 of the terrain. Certain degradational processes remained activealong the southwestern margin of the site and at a few locations within the site in

.- 1981. Such continuous, long-term modifications of permafrost terrain as the re-sult of man's activities have not previously been documented.

The East Oumalik site was studied from 1978 to 1981 to determine the re-sponse of near-surface materials and processes to the drilling activities of 1950and to define the degradational processes that modified the site to its presentcondition. Near-surface geology was defined mainly by field and laboratoryanalyses of disturbed and equivalent undisturbed parts of the upland. These

*analyses included coring 76 holes of 1.5- to 34-m depth within representativeparts of the upland and also augering 360 holes of 1.5-m depth along transectsacross it. Frozen and thawed samples from the cores were analyzed for variousphysical attributes, such as grain size distribution, moisture content, ice volumeand Atterberg limits. Similar analyses were made of material from another olddrill site, Fish Creek, in order to compare the effects of disturbance with those atEast Oumalik.

The East Oumalik drill site was established upon a moderately drained, low re-lief upland surface composed of perennially frozen, ice-rich silt. Terrain disturb-ances, such as bulldozing of roads, excavation, construction of camp structures,and off-road vehicle trafficking, disrupted the thermal regime of the frozen silt,causing thawing of the permafrost and a subsequent thickening of the active lay-er. Melting of the ground ice, which composes 42 to 90% by volume of the upper15 m of the frozen silt, caused subsidence and initiated slumping, gravitationalflow and collapse of slope material into the subsiding areas. Depressional areasbecame interconnected as lateral slope erosion and active layer thickening con-tinued beneath individual disturbances. Thermal and hydraulic slope erosion wasextensive in drainage ditches and wherever drainage channels formed withintrails, wedge troughs and other sloping thaw depressions. Degradational proces-ses were probably most active for 10 to 15 years after disturbance, with activitygradually diminishing to its present level.

Lateral erosion caused the impacted area to be larger than the area initiallydisturbed. Such lateral expansion was facilitated by the high ice content of thesilt, the frequency and large dimensions of wedge ice, the instability of the siltupon thawing, and local variations in relief, including those that developed asthaw subsidence took place. At this site thawed silts are saturated to oversatur-ated and their water contents immediately after thawing are significantly greaterthan their liquid limits; furthermore, their liquidity index indicates that the mater-ials are at failure upon thawing. Lateral expansion and deepening of subsidingareas apparently ceases only after enough sediment has been deposited in thethaw depression to retard thaw bulb expansion and permit slope stabilization.Deposition results when the drainage gradient between interconnected troughs islost or when insufficient meltwater is available to remove the sedimentssloughed into depressions by rapid headward erosion of degrading slopes.

vi

The upland has been transformed from a low relief and relatively featurelesssurface into an irregular, hummocky surface with numerous depressions, many ofwhich are filled with water year-round, Relief across the site was modified fromless than 2 m to greater than 8 m, with individual depressions up to 5 m deep. Sea-sonal thaw depths mostly reflect the new topography and moisture conditions ofthe disturbed areas. They are generally deeper than in undisturbed terrain adja-cent to the site, and they may not be in equilibrium with the modified terrain.

A comparison of the disturbances and degradational processes at East Ouma-Ilk to those at the Fish Creek drill site (175 km to the northeast) indicates that theseverity of disturbance is greater at East Oumalik. This dissimilarity results pri-marily from differences in the physical properties of the near-surface sedimentand terrain, and the types of degradational processes initiated because of theseproperties. In particular, the dimensions and volume of ground ice, mechanicalproperties of the sand and lower relief of the upland were critical factors limitingthe physical modifications of Fish Creek to those that result from thaw subsi-dence and consolidation.

This study indicates that geotechnical investigations of the subsurface mater-ials for selection of construction sites must include an analysis of the content anddistribution of ground ice to determine the properties of the sediments uponthawing. The impact of disturbance at East Oumalik indicates that in morphologi-cally similar areas of fine-grained, ice-rich sediments, adverse physical changeswill take place over an extended period of about two to three decades if the vege-tative mat is altered by either removal or severe compaction.

vii

LONG-TERM MODIFICATIONS OFPERENNIALLY FROZEN SEDIMENTAND TERRAIN AT EAST OUMALIK,NORTHERN ALASKA

Daniel E. Lawson

INTRODUCTION Lawson 1979). The distribution and volume ofice in near-surface materials are thus critical fac-

The impact of man's activities on the natural tors in determining the effect of disturbance onprocesses and properties of arctic tundra de- permafrost terrain. Because of the importancepends largely on the effect of these activities on of these factors, Ives (1970) proposed that differ-the thermal regime at the ground surface. Most ences in the susceptibility of permafrost to dam-

arctic regions are underlain by perennially fro- age by disturbance could be approximated as a

zen ground, which may contain substantial ratio of the volume of ice in the permafrost to

amounts of ice (e.g. Black 1969, Mackay and the mean annual ground temperature.Black 1973, Sellmann et a). 1975, Pollard and Although a number of studies have examined

French 1980). Disturbance of the tundra general- the short-term effects (about 10 years or less) of

ly reduces the insulating effect of the vegetation man's impact on permafrost terrain (e.g. Hegin-

and uppermost soil horizon, causing an increase bottom 1973, Radforth 1973, Rickard and Brown

in the mean annual temperature at the ground 1974, French 1975, 1980, Berg and Smith 1976,surface and thus in the annual depth of thaw Adam and Hernandez 1977, Abele et al. 1978),

i (e.g. Muller 1947, Brown et al. 1969, Mackay the response and recovery of permafkost terrain

1970, Heginbottom 1971, Viereck 1973, Brown to disturbance after longer periods of time has

" and Grave 1979). Melting of ice in the near-sur- been only poorly documented (Grave and Nekra-

face materials causes the ground surface to sub- soy 1962, Hernandez 1973, Isaacs 1974, Lawsonside (e.g. Muller 1947, Terzaghi 1952) et al. 1978, Lawson and Brown 1979). With the in-

Following disturbance of ice-rich tundra, thaw crease in development of arctic tundra regions,

subsidence often modifies the drainage so that an understanding of the long-term effects is

some areas remain wet for longer periods of needed. This will allow a realistic appraisal of

time during the year while others become much the terrain's sensitivity to future developmentdrier. The increase in moisture collected in the and govern the techniques that must be utilized

active layer of depressional areas also results in to prevent unwanted environmental changes.greater heaving of the ground surface in winter Old drill sites in the Naval Petroleum Reservewhen it freezes. Increased thaw may induce oth- Number 4 (PET-4), now designated the Nationaler thermokarst-rplated processes, such as the Petroleum Researve-Alaska (NPRA) (Fig 1), pro-

* slump or flow of slope materials or the gullying vide examples of the effects of camp construc-

and removal of sediment by erosion in areas tion and drilling operations on permafrost ter-with sufficient local or regional relief (e.g. rain after approximately 30 years. From 1944 to

Muller 1947, Ferrians et al. 1969, Mackay 1970, 1953, the U.S. Navy drilled 36 exploratory wells

French and Egglinton 1973, How 1974, French in a variety of the geologic, topographic and cli-

1974, McRoberts and Morgenstern 1974a, b, matic settings in PET-4 (Reed 1958).

A ARCT c OCEAN', 1o Camp Beaufort,

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':"AtkasookFishCreek

Cumolik 00

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S'" ~ Umiat .,-'

River

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162* 160°

158* 156- 1540 1520

Figure 1. Location of the East Oumalik, Fish Creek and Oumalik drill sites inthe NPRA.

From 1978 to 1981, I examined the effects of analyses of equivalent undisturbed areas r xt todrilling activities that took place in 1950 at the the camp and exploratory well. These areas '/ere

East Oumalik drill site (69047 ' 29" N, 155032'39" identified by comparing the terrain and vegeta-W). The primary objectives of this study were to tion of the site and that of adjacent areas on ae-analyze the response of the near-surface mater- rial photographs of the upland in 194.1 and 1978.ials and surficial processes to those activities Because no observations were made on the siteand define the degradational processes that between 1951, when it was abandoned, andmodified the site to its present condition. The 1978, when this study began, the degradational

analyses indicate that various cryogenic and processes had to be interpreted from the ero-sedimentologic processes were initiated that sional effects and sedimentology of the depositshave caused extensive modification of the ther- of these processes. Wherever possible, trenchesmal regime, ground surface and drainage of the were dug to examine the sedimentology of dis-site. Comparison with another PET-4 drill site, turbed and undisturbed near-surface materials.Fish Creek, indi( ate, the importance of the pro- Near-surface sediment and soil of the acti~.eperties of near-surfa(e materials in determining layer and perennially frozen grouno in disturbedthe extent of I)hwis( al , tedification that took and undisturbed areas were sampled by coring.place Drill holes were located upon representative sur-

ficial features and along transects across dis-

turbed and undisturbed terrain. A total of 76METHODOLOGY holes were cored to depths ranging from 1.5 to

34 m. An additional 360 holes of 1.5-m depth andStandard geologi(al te(hniques were used to spacing of 2 m were augered along two tran-

analyze the response of the Last Oumalik site to sects. Detailed results of the drilling program

disturbance in 1950-51 Details of the near-sur- will be presented in a subsequent report in pre-face geology of the drill site prior to its occupa- paration.tion were defined mainly by field and laboratory

2

The geology of each drill hole, including the slope angles of 5o to 150 (Johnson 1978). Sedi-type and distribution of visible ground ice, was ments underlying the region are perennially fro-logged. Frozen and thawed samples were select- zen and consist mostly of Quaternary silt anded for laboratory analyses that included grain fine-grained sand (Black 1964, Williams et al.size distribution, moisture content, ice volume, 1978). Stratigraphic logs of the East Oumalik ex-organic content by loss on ignition, bulk density, ploratory well indicate that bedrock lies at aand liquid and plastic limits. These data were depth of about 30 m beneath ice-rich silt thatused to calculate various parameters such as de- contains sporadic lenses or layers of fine sand or

* gree of saturation, porosity, void ratio and tex- clay. These materials are continuously frozen totural statistics. a depth of 267 m (U.S. Navy 1951).

The site was surveyed using a self-leveling le- The camp and exploratory well were estab-vel and rod. Active layer thickness was mea- lished upon a mostly featureless, gently slopingsured by probing to refusal with a steel rod. and moderately drained upland surface (Fig. 3)

that is bounded on three sides by slopes ofstream valleys (Fig. 4). The main stream on the

GEOLOGICAL SETTING southern and western sides of the site is en-trenched about 15 m and meanders northward to

East Oumalik lies approximately 170 km the Oumalik River. This valley bottom containssouth-southeast of Barrow, Alaska, near the cen- meander cutoffs, small drained lake basins andter of the NPRA (Fig. 1) and just north of the marshes (Fig. 4). Solifluction lobes lie on the low-boundary between the Arctic Coastal Plain and er half of the valley slopes. The beaded tributaryArctic Foothills Provinces (Wahrhaftig 1965). stream on the northern margin of the site flowsThis region is characterized by upland surfaces within the upland materials.cut by meandering streams and active, often With the exception of linear patterns from ve-deeply incised, thaw lakes (Fig. 2). Relief be- hicle tracks north of the site, disturbance result-tween the uplands and valley bottoms, including ing from man is not evident in the 1948 aerialdrained lake basins, ranges from 3 to 20 m with photograph (Fig. 4). Thermokarst resulting from

155030'

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0/- 6 / -69-45 '

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Figure 2. Topographic map of the region surrounding the East Oumalik drill site(from USGS Ikpikpuk River Quadrangle, 1956). Contour interval in feet.

3

Figure 3. Undisturbed upland surface looking east of the former drill site in 1980.

natural processes was more prevalent elsewhere ice by volume. Both estimates are comparableon the uplands. Gully entrenchment, thermal to the values I measured in samples analyzed forerosion and other processes have modified the this study.drainage and developed areas with well-definedpolygonal trough patterns. A few locations in theregion exhibit large areas of thermokarst next to CAMP CONSTRUCTION AND OCCUPATIONvalley slopes that are apparently still expandinglaterally into upland sediments. Retrogressive The East Oumalik site was constructed andslumps and flows have modified valley-marginal subsequently occupied from April 1950 throughsediments at other locations. Such features indi- mid-January 1951. The drill rig, camp buildingscate the presence of frozen sediments with rela- and other equipment were moved overland fromtively high ice contents and thus their potential the Oumnalik drill site (Fig. 1) by sled-train duringsusceptibility to reworking by thermokarst pro- April and May of 1950 (Reed 1958). Suppliescesses if disturbed (e.g. French 1975). were also freighted on C46's and C54's during

Livingstone et al. (1958) used the process of April from Barrow to an airstrip located on a fro-thaw lake formation (e.g. Black 1969, Tedrow zen lake about 5 km from the East Oumnalik site.

41969) to estimate the quantity of ground ice that Camp construction began shortly thereafter,melted during the formation of a thaw lake in with the well being spudded on 23 October 1950.upland sediments located about 6 km east of the Drilling continued until 30 December 1950 withEast Oumnalik site. They estimated that ground the hole officially abandoned on 7 January 1951.ice composed 68% by volume of the upper 28 m The camp was then dismantled and the equip-of sediment in which the lake formed. Williams ment freighted by sled-train to Barrow over the

4and Yeend (1979) similarly estimated that a Oumalik trail (a main artery between Barrow anddrained thaw lake near Umiat had developed in lUmiat which passed through the site).perennially frozen silt containing 78% ground

4

4"

Figure 4. Aerial photograph ot the East Oumalik drill site on 6 September 1948 (BAR-124-147) prior to occu-.. patiott. Dashed line marks the camp boundary; black line outlines approximate area of activities. Examples

- of natural thermokarst in the region include (1) headward expansion and deepening of small gullies by ther-4 mal and mechanical erosion, (2) slump and flow of valley-marginal sediments, and (3) degrading upland ma-* terials next to a thaw lake.

5

'-7

a. Drilling rig.

|7;

II

'I

b. Derrick, camp buildings and other equipment used at East Oumalik.

Figure 5. Equipment in use in 1949 at the Oumalik drill site before tear-down and transport to the EastOumalik site in 1950.

The principal camp structures were 6.1-x walks, also on piles, joined many of the build-12 2-m (20- x 40-ft) Quonset huts used for a mess ings.hall, a galley, an oilfield warehouse, a recreation Drilling equipment included a Wilson Superhall and sleeping quarters; a lamesway hut also Titan rig, Ideco derrick and associated equip-used for sleeping quarters; and 11 wanigans used ment such as boilers, generators, cementingfor offices, shops, sleeping quarters, a latrine, units and mud and water tanks (Fig. 5). Vehicles

4 and water and equipment storage (Fig. 5). Build- used on the site included two weasels, an LVT, aings were supported by 1.2-m to 2.0-m-long wood D-8 Caterpillar dozer, a D-6 Caterpillar dozer, aor steel piles driven in* the permafrost. Board- TD-9 cherry picker, a Northwest crane and a

6

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forklift. Vehicles also transported supplies and TYPES OF DISTURBANCEwater to the camp from the airstrip and nearbystream (U.S. Navy 1951). The types of disturbance-camp activities

The drill was set on a foundation of 30.5-x and construction-can be categorized accord-30.5-cm (12-x12-in.) timbers beneath which a re- ing to the first physical modification theyfrigeration system was connected. This system caused. These categories are: 1) trampling andconsisted of 2.5-cm (1-in.) pipe cleated to the un- compaction of the organic mat including the liv-derside of each timber and through which me- ing vegetation, 2) killing of vegetation, 3) remov-chanically cooled diesel oil was circulated. This al of the vegetative mat and 4) removal of near-system was installed to prevent thawing of the surface sediment with vegetative mat (Table 1).ground beneath the rig (U.S. Navy 1951). This grouping is similar to that proposed by How

The layout of the camp and activities on the (1974), and by Grave (in Brown and Grave 1979).site were unfortunately poorly documented. The Each type of disturbance is described in moredrill rig, derrick and most camp buildings were detail in Table II of Lawson et al. (1978).removed in 1951, but items such as the rig foun- The response of the site to the various activi-dation, wooden structures constructed on site, ties differs according to the degree of alterationpiles and solid waste were left behind. The de- to the thermal regime of the affected area. Com-bris remained scattered across a 3-km 2 area in paction of the surface organic material or killingand around the camp's location in 1978 and was of plants modifies the thermal properties of theused to construct a map showing the approxi- vegetation, soil layer and possibly underlyingmate locations of structures, roads, excavations sediments, causing a reduction in the insulatingand dump areas (Fig. 6). This camp appears typi- properties of the surface materials during thawcal of others in PET-4 that are described in more (see for example, R.J. Brown 1963, Bliss anddetail by Reed (1958). This camp has since been Wein 1971, Heginbottom 1971, 1973, Linell 1973,cleaned up and the debris was either removed or Mackay 1970). However, the severity of tramp-buried in a pit excavated on-site in 1980-1981 by ling and compaction or the rate at which the ve-NPRA clean-up crews. This burial pit is located getation is killed can vary, resulting in some var-south-southwest of the original site in previously iation in at least the initial effect of disturbance.undisturbed upland materials. Areas affected by removal of the vegetative mat

Table 1. Classification of disturbance by activities and their initial modification to vegetation, soils andsediment.

Type ofdisturbance Initial modification Types of activities

I Trampling and compa(tion of a Off-road vehi(le novements. single a1n(d multiple passes Vby wheeled andvegetation ski-mounled vehi( les

b Snowpads (e g winter trails)

I F ootliathsd ]emlporary storage of supl)lies

2 Killing of original vegetation d Hydrocarbon %pills (diesel fuel, (rank(,i{, oil)b Hoardwalk and (levated buildings( Soli( waste (e g steel drums, larps, woo(l is, nonclegra da hi, wa sh,)d Iverm, (,poil piles) formed along bulldoed trails and ex( avaios

Renoval of vegetativi' mat a Shallow bulldo/ed roadsb Shallow e( avations for bUh dirig founrdations

( Piling (lo(al)d I ra( ked vehle rioveienis

4 Removal of near-surface sediment a fItulldoed roads

with vegetative mat b I x( ovfioiior tren( hes, draina di( hlis a (n sotimnpB( Iasement em avations for drill rig piiling

8

4

a. Former location of timber beam foundation for drill rig; pipes with re-frigerant were attached to the beams to retard thaw (disturbance category2).

b. Tilted steel pilings that formerly supported a camp building (distur-bance groups 3 and 2).

Figure 7. Lightly disturbed areas.

and upper soil horizons show the most extensive categories 3 and 4 (Table 1) are now character-and permanent changes, in some cases leaving ized by differential subsidence ranging from 3 tono trace of the initial cause of the degradation. 5.5 m, poor drainage with some standing water,Examples of areas affected by various types of an incomplete cover of vegetation and an active

4 disturbances are shown in Figures 7-10. layer thickness ranging from 0.8 to over 2 m.Areas at East Oumalik where the vegetative Areas in which the vegetation was simply killed

mat and soil were removed by the activities of but not removed by category 2 activities have 1)

9

Figure 8. Subsided area traversed by camp vehicles on northeast area ofsite (disturbance group 1).

Figure 9. Former bulldozed trail at northeast corner of former site (viewnortheast). Present ground surface is over 5 m lower in elevation than theoriginal ground surface (disturbance group 4). Polygonal trough pattern

• 0covers bottom.

10

Figure 10. Former drainage ditch on north margin of site; thermal and hy-draulic erosion developed channel over 3 m deep (disturbance group 4).

undergone a generally uniform subsidence rang- rain modification beyond the areas initially dis-ing from 0.1 to 1.1 m (typically 0.3 m), 2) become turbed.reasonably dry through most of the year, 3) been The primary reasons for this expansion arecompletely revegetated, and 4) developed a 0.3- three-fold: 1) the properties of the sedimentsto 0.6-m-thick active layer. made them highly unstable upon thawing, 2)

The degree to which compaction resulting both natural relief and changes in slope and ele-* from activities in category 1 has actually modi- vation due to thaw subsidence permitted runoff

fied the terrain depends upon the intensity of of meltwater and induced other degradationalcompaction and disruption to the uppermost or- processes, and 3) these degradational processesganic-rich soil horizon. For example, single-pass, perpetuated thermal disequiibrium and contin-off-road vehicle trails have minimal thaw subsi- ued expansion of thaw into adjacent near-sur-dence of 0.1 to 0.3 m with few other changes ex- face materials.cept in the composition of the vegetation, The increase in active layer thickness andwhereas multiple pass trails at East Oumalik deepening of the annual depth of thaw (taken asshow differential subsidence of up to 4 m, vari- the OC isotherm) which result from a local ter-able moisture and drainage conditions (often rain disturbance (Fig. 11a) are in general analo-with standing water), a mostly complete but gous to the development and expansion of amodified vegetation cover and active layer thaw bulb beneath lakes and rivers(Brewer 1958,thicknesses of about 0.6 to 1.5 m. Lachenbruch 1959). Ideally, the rate of expan-

sion of the thaw bulb is a function of effectivechange in temperature at the ground surface and

DEGRADATIONAL PROCESSES AND thermal properties of the sediment. Under iso-

* THE EFFECTIVE AREA OF IMPACT tropic and homogeneous conditions, the verticaland lateral expansion rate beneath a limited

The effects of camp and construction activi- area of disturbance will decrease with time untilties on the drill site were determined not only by it becomes stable (McRoberts 1978).the type of disturbance and its immediate modi- During thaw bulb expansion, however, melt-

fication of the terrain, but also by the more long- ing of ground ice will cause subsidence of theterm cryogenic and sedimentologic processes ground surface that is approximately proportion-initiated. These long-term processes are respon- al to the volume of ice in excess of the pore

S.sible for the extensive lateral expansion of ter- space of the sediment in an unfrozen state (see

11

!4

Q0

C CL

T 0

00

o C 0z C..

-~0 CD:3 0 CLC

.3-

CL Cu

0j

0

Ct -a

CUu0 -lC0

-CuL

____ 00.,C

'tz

o I .o ~Z~o12

-. ~ 0 '.

M~ 0~'0~

u~~o C c

q.

2

to tiEZi2 .,2' *~*

M cu cc 2 E

UO

CI

13a

for example, Morgenstern and Nixon 1971, Nixon If failure conditions are met repetitively and

and McRoberts 1973, Crory 1973, Nixon and Lad- thawed sediments undergo transport by massanyi 1978). If the meltwater flows away from the movement or are removed by meltwater duringsubsiding area, melting of the ground ice effec thaw subsidence, neither a stable physical condi-tively increases the depth to which thaw occurs tion nor a thermal equilibrium will develop.because insufficient sediment is released to Thus, the area of sediments affected by degrada-form an insulating cover. tional processes will continue to expand beyond

Melting of the ice during thaw consolidation limits defined by simple thaw bulb formation be-may also generate excess pore pressures that re- neath a disturbance.duce the strength of the thawed material (McRo- This "worst case" scenario represents the typi-berts and Morgenstern 1975, McRoberts et al. cal response to disturbance at East Oumalik (Fig.1978). Larger ice bodies (layers, large lenses and 12). As thaw began, melting of excess ice quicklymassive ice) can generate sufficient excess pore led to subsidence (Fig. 11b). Subsidence was sub-fluids to produce an unstable condition in over- stantial because of the high volume of ice in un-lying fine-grained sediment (Nixon 1973). These disturbed upland sediments. Samples containedmaterials will fail if excess pore pressures be- 40 to nearly 100% ice by volume (mean = 85%).come equal to the overburden weight of the Large ice lenses and ice wedges are common andthawed sediments. Remolding in response to compose an estimated 60% by volume of themovement can cause these materials to liquefy upper 10 m of perennially frozen upland mater-rapidly and flow. ials. The ice wedges range from 5 to 10 m in

Distonce (meters)(a) 0 10 20 30 40 50 60 70

, . .it5: - '0 T1 -

" - /Dots indicate

-" Ice

(b) 0 20 40 60 80 100 120 140 160

0 - .- Undisturbed Surfoce

* I , Surface4 ActiveLoyer

Drill -,Thickness

8X " Possible"- 8 ce -

. 0Dimensions

I (c) 0 20 40 so 0 100 120 140 160,7-

12

Figure 13. Stratigraphic cross sections of (a) undisturbed and(b, c) disturbed upland sediments at East Oumalik. Upper-most dashed line on (b) and (c) represents profile of theground surface prior to disturbance. Locations of ice were

" defined by drilling at indicated locations and in (a) by auger-ing to a 1.5-m depth every 2 m along the transect.

14

4i

width at the top and extend 7 to 14 m deep (Fig. (w-P w)13). There appear to be two sets of ice-wedge -(1)polygons, only one of which has surficial expres- (Lw-P)sion as a polygonal trough pattern. (where w is the natural water content, P the

The more rapidly subsiding areas were low- plastic limit and Lw the liquid limit) was usuallyered significantly below the elevation of the un- greater than 1. If I > 1, remolding will rapidly li-disturbed surface. The lateral slopes of these de- quefy the material (Terzaghi and Peck 1967).pressions were stable intially because of the Failure of such thawed materials on a slopingpermafrost within them, but this increase in re- permafrost surface will take place at very lowlief then became a factor in the lateral expan- slope angles (<150) (Morgenstern and Nixonsion of degradation. 1971).

The slopes bounding the depressions became Comparison of the in-situ water content and Ii-highly susceptible to failure as thawing laterally quidity index clearly demonstrates the inherentexpanded because of the physical properties of instability of the silt after thawing (Fig. 15).the sediments (particularly ice content). Undis- Based upon these data and comparison to dataturbed perennially frozen sediments of the up- of Nixon and Hanna (1979) and others, it is highlyland are rather homogeneous and composed of probable that the thawed silt had little or no

moderately sorted, medium silt (Fig. 14). Most shear strength. Melting of the prevalent massive

samples had a bimodal size distribution with pri- ground ice undoubtedly was also responsible for

mary modal sizes of coarse and fine silt. local increases in pore pressure and loss ofThe condition of the silt after it thaws is indi- strength. As a result of the silt's instability after

cated by its in-situ water content, degree of sa- thawing, gravitationally induced slope proces-

turation and liquidity index. Samples of undis- ses, including slump, debris flow and liquefied

turbed silt of the upper 15 m of upland had wa- flow, became active (Fig. 11c). The oversatur-ter contents ranging from 45 to 500% of dry ated silt also offered little resistance to hydrau-

weight (typically 70 to 160%) and most were lic erosion from meltwater flowing off the thaw-oversaturated. Similarly, the natural water con- ing slopes and within thaw depressions. Initial

tent of the thawed silt was usually greater than slope failures may have resulted from slumping

its liquid limit. The liquidity index I, of the silt, along the interface between thawed sediment

as defined by the ratio: and frozen sediment (or ice) after excess pore

100-

IA80 /

60

50, Ic

40 , 0 -

:_C 240-U , , *r

S30 - ~'

20 , 2i o

0-2 0 4 6 8 I0 -2 0 2 4 6 8 10

Phi Size Phi Size

a. Frequency curves. b. Cumulative curves.

Figure 14. Representative frequency curves (a) and cumulative curves (bi of grain size distribution of sam-

pies from upland silt (<10-m depth) at East Oumalik. Frequency curves computed by numerical differentia-

tion.15

•••part of the slope. Differential thawing rates ledto further degradation of the upper slope mater-

10.0 • ials at some locations, while at others, thawingo * was reduced sufficiently to stop spalling. At

these latter locations, vegetated tundra blocks0 soLremain perched at the top of the slope today

°° (Fig. lid). Similar blocks are also buried in sedi-1.0- ments of thaw depressions.0 - Several conditions developed to retard thaw

bulb expansion and stabilize slopes (Fig. lid).These conditions included 1) thickening of sedi-

-5.0 -- - ments in the thaw bulb due to thaw or deposi-0 100 200 300

In situ Water Content (% dry wt.) tion, including that at the base of depressionalFigure 15. Water content of fro- slopes, 2) deposition and/or differential thawzen undisturbed silts compared to along the longitudinal axis of gullies to reduce orher luditrbe ilts. celiminate the drainage gradient, 3) reduced melt-

twater production, perhaps as massive ice melted

completely or as rates of thaw slowed due topressures had reduced the shear resistance here sedimentation, and 4) revegetatio, af the bot-to less than the gravitational force (Terzaghi toms and lower slopes of depressions. Snow1950, Morgenstern and Nixon 1971). Lateral ex- banks that form within depressions and gulliespansion of thaw depressions by slope failures also slowed spring thaw and iocally reduced the

* eventuaily caused coalescence of depressions length of the melt season. Vegetation grows onthat had initially developed beneath unrelated much of the disturbed site today, with bare areasdisturbances. limited to the bottoms of the largest depres-

Meltwater flowing from the thawing sediment sions, the upper parts of steep near-verticaland from surface runoff created channels in sub- slopes, and the locations where solid debris wassiding areas beneath bulldozed roads. drainage removed during clean-up of the site in 1980. Con-ditches, polygon troughs and other inter( on. sidering the types and interrelationships of thenected thaw settlement features Thin1l lani degradational processes and the condition ofnated deposits in some of the former (h irmtI, the site from 1978 to 1981, the degradationalindicate that meltwater flow eroded and rted(i,'ri pro( esses were probably most active for 10 to 15buted sediments that had been transprt,.(I wt- ears following disturbance with activity dimin-the depressions by the mass wastnir w- - -.- shing sin( e then to its present level.The coalescence of depressions tormin t,.n, .,,t Areas that were not intensely disturbed (e.g.adjacent areas of disturban(e, alst, rt,,,, ., it, single oft-road vehicle passes, areas beneathgully formation wherever sutti( ent wdi,,i.nt huldings or next to piles) underwent thaw subsi-isted. Closed thaw depressiow som. "ith h,,n den, e. hut were generally unaffected by othernelized flow into them, filled viith rnltas er degradational processes. Thaw subsidence de-

When subsidence rates were mu( h grq-ater veloped smaller depressions without well-de-than rates of lateral expansion, steep, near erti tined slopes so that erosional processes werecal slopes developed (Fig. l() Su h slopes also less active Deeper subsidence in these areas re-developed when bank sediments of low (e (on- sulted from the partial melting of ice wedges.tent were adjacent to subsiding areas of high 0iecontent. These slopes did not fail immediatelybecause the frozen sediments outside the thaw AREAL EFFECTSbulb provided strength and stability. Differential OF DISTURBANCErates of thawing eventually induced tensionalfracturing of the sediments and vegetative mat The degradational processes resulting fromat the top of the sl,,)pe. As these materials be- disturbance have caused a substantial reshapingcame oversteepened, they underwent spalling or altering of the upland topography, drainage,and collapsed into the depressions. Banks ot near-surface sediments, vegetation (Kom~rkovAhigh ice content also failed by slump and flow. and Webber 1980) and soils.* These changesColluvial deposition in depressions retarded thisthawing and enhanced the stability of the lower "K R Everett, Ohio State University, pers comm . 1981

160

have apparently led in turn to a permanent areas in the disturbed parts of the upland arechange in the near-surface thermal regime of the now much wetter year-round. Across the site,site. water remains ponded in depressions between

drier hummocks and in trenches located above

Topography partly melted ice wedges; some of these have re-Surficial changes in the site are clearly evi- mained water-filled (up to 1.0 m deep) from July

dent on aerial photographs taken in 1978 (Fig. 1978 to September 1981. Individual depressions16). The relatively featureless upland surface on are often closed basins with water perched inthe 1948 aerial photograph (Fig. 4) is now cov- them above impermeable permafrost and withered by hummocks and depressions with a distri- individual basins separated by dry hummocks inbution controlled by the former location of the which the permafrost is closer to the surface.camp and vehicle trails. Depressions, up to 5.5 m Most former drainage ditches and interconnect-in depth, are mostly irregular in shape, size and ed depressions have water flowing in them dur-distribution (Fig. 17). The deeper depressions are, ing melting of the snowpack, but they containhowever, generally interconnected with drain- only standing water in isolated depressions dur-age ditches or gullies located on the valley ing the remainder of the year. Snow that drifts in-slopes. Relief across the site exceeds 8 m, where- to the various subsidence features in winter mayas relief was probably less than 2 m prior to oc- remain in the deeper depressions until late July,cupation. A polygonal pattern of troughs formed thus reducing the length of the thaw season andby the melt-out of ice wedges is apparent in the inhibiting water flow at these locations. Theseless intensely disturbed areas of the site (Fig. 16). snowbanks provide local sources of meltwaterIt is also present in the bottoms of some of the later into the summer than elsewhere on the up-larger and deeper depressions (Fig. 9). land.

Groundwater, surface Sediment properties andwater and drainage near-surface stratigraphy

Observations and measurements at different Properties of sediment beneath disturbedtimes throughout the year in Lndisturbed areas areas have been modified so that they now gen-of the upland indicate that the water content of erally differ from undisturbed active layer andthe active layer varies with the microtopography perennially frozen materials. Thawing has elimi-of the upland but shows relatively little point-to- nated the massive and segregated ice of the up-point variation. During winter, snow accumula- permost permafrost, while thaw consolidationtion is low on the upland (less than 40 cm) due to has increased the particle packing and de-lateral wind transport of the snow to other areas creased the pore spaces and voids in the dis-of higher relief. The snowpack melts rapidly in turbed sediment (Fig. 18). As expected, no signifi-spring and is normally completely dissipated by cant change in the grain size of the surficial sedi-mid-June. Runoff from snowmelt moves off the ments was found. Moisture contents have beenuplands in small rills (channels of 2- to 10-cm reduced and usually range from 18 to 40% ofdepth) between the tussocks on valley slopes dry weight in hummocks and up to 120% of dry("water tracks") and in somewhat larger (10- to weight in wet depressions. Ice volumes of sea-

* 20-cm-deep) polygonal troughs above ice sonally frozen sediments show similar variationswedges. Subsurface flow occurs on top of the and rarely exceed 50%. Bulk density in thesemineral soil at the base of the surface organic samples ranges from 1.6 to 1.9 g/cm'. an increaselayer and at the interface of the unfrozen and of about 30%. Porosity shows a comparable de-frozen horizon in the active layer. By summer's crease in value. The degree of saturation ofend, shallow groundwater from melting ground disturbed sediments in the frozen or unfrozen

i ice flows through the active layer on the upper state is consistently near 1 0 (saturated condi-surface of the permafrost. Standing water is gen- tion). The moisture content, ice volume and por-erally restricted to the small troughs above ice osity of disturbed sediments are less than in thewedges and to the deeper depressions between frozen active layer and perennially frozen sedi-tussocks, ment of the undisturbed upland. Density is also

As a consequence of the topographic changes significantly higherthe distribution and movement of both surface Disturbed sediments also bear several newwater and shallow groundwater flow above characteristics that were developed during de-permafrost have been substantially altered. Low gradation In undisturbed areas, a peat horizon

17

Cc'

to00

00

-Z 0 o :

'~7B

0,A

8,11

~ 0 50 10 10 00 25 30 350

~~019 8P

50 10 ISO 200 20 30

199

o 03

00*

WE-

NCA C,

C?- -t-- -------

-0

00 -

o) 0

0 0E__ _ __ _ _ .> . Co - a

C)I [!) Q

O 00 0

00 .t I-S,

a) C): -c -

1) 0-

C C.

00w 0-.

C V6

*20

_---- '-- - - - ----- - Organics and silt__ _~~_ a dded from thawing

slopes by degradation- - - - .- processes

Original 77-~~soil horizonz € 'l %%before disturboncet - Active layer thickness

- -I before disturbance

Initial depthDeformed-_ - -- -othaw dOrai

peat horizon - ---'----.-. ,, A ofthow Organic-,' ---_--_- - "- rich silt

--.- ---h released by- t 's melting of

__oon lj lice wedgeSeeas Disturbed depthice veinsthw

I Wedge

Figure 19. Stratigraphic profile observed above partly meltedice wedge at East Oumalik. Peat horizon was located on topsurface of ice wedge before melting began. Organic-rich silt ofthickness h2 was melted from the wedge and deposited in situ.Measurements of h, typically range from 0.35 to 0.60 m and ofh2 from 0.05 to 0.35 m.

commonly lies on the top surface of ice wedges. as excess ice melted and thawed sediment con-As these ice wedges melt because of disturb- solidated. The mass movement of slope materialance-induced thawing, they release the sediment onto oversaturated sediments in depressions al-and organics that are contained in the wedge so occasionally caused some to become convo-ice. This material is immediately deposited in luted.situ between the peat and the remaining wedge Slope processes also modified the stratigra-ice. The thickness of this layer (h, in Fig. 19) is phic profile in depressional areas by 1) buryingthus determined by the material content of the soils beneath slope-derived material, 2) trans-ice wedge-typically 0.5 to 5% by volume porting and depositing intact blocks of the tun-(mean 2.2% of 20 samples). This zone of melted- dra vegetation and soil, and 3) producing strati-out sediment was up to 0.35 m thick in the deep- fied sediments due to interspersed, repetitive pe-est depressions on the drill site. In each of the 10 riods of meltwater and sediment flow deposi-sequences above partly melted ice wedges exa- tion.mined, I found no indication of a contribution ofsediment from the lateral slopes. Surficial processes

This peat-sediment-wedge ice sequence is Most of the site no longer appears to be de-therefore a product of the disturbance-induced grading physically; however, some degradation-thaw at East Oumalik. This stratigraphic se- al processes remain visibly active along thequence may also be applicable elsewhere for de- southwestern margin of the disturbed area andfining areas where thaw depths have been in- locally within the site. The most important in-creased in the geologically recent past in re- elude the following:sponse to climatic or other natural modifica- 1. Thermal degradation and ground subsi-tions of the thermal regime (see Brown 1967, Fig. dence. These processes are active on the5, for a similar sequence above a buried ice southwestern margin where they are ex-wedge). panding thermokarst into apparently un-

Soil horizons and sedimentary stratifications disturbed parts of the upland (Fig. 16). Anwere folded and reoriented at several locations ice wedge exposed in a collapsing bank of

21

a thermokarst pond in 1978 subsequently depths of disturbed areas in July 1978 to thosemelted by 1980 and became a 2-m-deep de- from similar undisturbed areas of the uplandpression filled with water year-round. and adjacent stream valleys (Fig. 21) suggests

2. Spall and collapse. Spalling also appears to that factors such as drainage, presence of stand-be active in modifying steep slopes that ing water, topography and type of vegetationbound at least two of the deeper thaw de- may be determining the disturbed area's presentpressions on the former site. Fresh blocks seasonal thaw depth.of the vegetative mat and soil, typical of A more detailed analysis is required, however,those released by spalling, occur at the to determine if the new physical and thermalbase of these slopes, conditions are in equilibrium or if the seasonal

3. Mechanical and thermal erosion. Runoff in depth of thaw is still changing. The ice wedgesgullies remains important during peak flow which were exposed in 1978 and 1980 near theperiods, with some transport of sediment southwestern margin of the site are clearly indic-from the site into the adjacent valleys. The ative of continuing thermal modifications insediment appears to be derived mainly these previously undisturbed areas. Thermalfrom areas of bare ground and from collu- modification is also probably continuing to a Ii-vial material previously deposited by mited degree around the larger thaw depressionsfreeze-thaw and other slope processes. and slopes within the original site. For the re-

4. Freeze-thaw. Sediments exposed across the mainder of the site, which appears physically in-site are susceptible to freeze-thaw proces- active, it could not be determined by this studyses, which cause cracking and loosening of if thermal changes are continuing.aggregates of sediments in slope faces. The Unfortunately, there are few studies whichsediments move downslope by falling and have examined the length of time necessary torolling under the force of gravity, achieve thermal equilibrium at a disturbed site.

5. Eolian activity. Unvegetated, dry sediments Most of these studies have examined a site'sexposed at the tops of slopes bounding de- thermal stability for only a short time (10 yearspressions and hummocks are eroded and or less) after the initial disturbance. Some sitesblown about on windy days. have apparently reached thermal equilibrium in

this time frame (e.g. Mackay 1977), while othersDepth of thaw continue to show thermal modifications (e.g.

The seasonal depth of thaw beneath the drill French 1975, Viereck and Dyrness 1979, Vierecksite appears to be permanently altered. Active 1982). None of the studies provides sufficientlayer thicknesses measured by probing with a data to allow correlations between sites with dif-steel rod in July 1978, September 1979 and Sep- ferent types of disturbances or physical condi-tember 1981 were thicker and had a wider range tions. Studies by Linell (1973) and Viereck (1982)in value in disturbed areas than in the undis- however, indicate that the development of aturbed upland. In July 1978, for example, this dif- deep organic layer is probably very important inference in active layer thicknesses ranged from stabilizing active layer depth. Because of the10 to 90 cm between disturbed and undisturbed complex interaction of physical parameters that

areas. affect the thermal regime of a disturbed site,Within the disturbed upland, active laypr there are undoubtedly substantial differences in

thickness varies with the present topography and the length of time over which thermal as well asdrainage conditions (Fig. 20). Largest active layer physical changes will take place.thicknesses occur in depressions developed by An additional factor affecting both thermalremoval of the vegetative mat and soil by bull- and physical response (which could not be eval-dozing, or in former gullies developed by ther- uated for this study) is thermal disequilibrium

4 mal and hydraulic erosion. In less intensely dis- between the present climate and the permafrostturbed areas, such as beneath buildings and oft- of the region Other upland areas in this regionroad sites, thaw depths in depressions are gener- are now developing thermokarst in response toally lower by 30 cm or more. natural processes If a disequilibrium condition

The active layer thickness of disturbed areas exists, even a slight disturbance could cause de-may now represent thermal conditions deter- gradation to spread progressively into adjacentmined by the present physical conditions of the undisturbed areas and the intensity of distur-site, suggesting that the depth of thaw may be bance would not necessarily be related to theapproaching equilibrium. Comparison of thaw impact resdting from disturbance. The present

22

coJ

c

Ch

u

en

4r

-05a

C

23

UNDISTURBED TERRAIN DISTURBED TERRAIN

Stream Dry Valley Slope Upland Deep Slopes Bounding Shallow I Slightly iEdge Marsh Valley Lower Upper Polygon Polygon Depressions Depressions Depressions Modified Hummocks Channels Berms

Terrace (wet) (dry) Center Trough (wet) (dry) (upper) (lower) (wet) (dry) Upland

0*0

3.

50- :.o So.

3 0 ,o,00

0 0!

5, I I

t;t

4 100

L .

Activelydegrading

Figure 21. Comparison of active layer thickness in July 1978 in disturbed and undisturbed parts of upland and sur-rounding stream valleys.

activity of degradational processes near the basins and a stream valley (Fig. 22). The upper-site's southwestern margin may partly represent most 5 to 10 m of this upland is composed ofsuch a response. Further analysis is required be- moderately well-sorted, fine sand (Fig. 23) of eo-fore the thermal stability or instability of the lian origin (Carter 1981).Last Oumalik site is understood. Drill holes encountered very few ice lenses in

undisturbed upland sand with visible ice re-stricted mainly to pore ice (Fig. 24). Ice wedges

COMPARISON TO FISH CREEK range from 1.1 to 2.4 m in width at the top andextend about 1.5 to 3.2 m below the surface. At

Another old drill site in the NPRA, Fish Creek, this site, ice lenses occur more frequently in the175 km northeast of East Oumalik (Fig. 1), was sand and silty sand of the lake basins, but iceexamined in 1977 and 1978 to define the physi- wedges here are comparable in size to those ofcal and biological modifications that resulted the intervening uplands. The upland surface isfrom drilling activities that took place from relatively flat with tussock tundra vegetationMarch through October 1949 (Lawson et al. covering undisturbed areas. Maximum relief be-1978). I later examined the properties of near- tween the upland surface and bottom of the lar-surface materials in 1979 and 1980 for this study, gest lake basin is about 5 m. Construction activi-by coring 45 holes ranging in depth from 2 to 15 ties in 1949 were mostly confined to the uplandm and analyzing their properties using the same areas, but vehicle movements, drainage ditchestechniques as described earlier for samples from and trash dumps disturbed parts of the drainedEast Oumalik. lake basins (Fig. 22).

The camp and exploratory well at Fish Creek Although both sites experienced occupationwere established upon a moderately drained up- for about the same length of time during theland surface next to two naturally drained lake

24

Figure 22. Aerial photograph of the Fish Creek drill site in 1977. Camp activities were mostly confined to anupland area composed of eolian sand. Drained lake basins east and south of the main camp and the streamvalley to the west were also locally disturbed by bulldozing, vehicle movements and trash dumping. Theconcrete drill pad 1), buildings on pilings 2), bulldozed roads 3), off-road trails 4), multiple pass off-roadtrails 5), bulldozed drainage ditches 6) and a steel drum pile 7) are indicated.

same seasons and were disturbed by nearly iden- a ratio of the final area of impact (Afd) to the ini-tical activities, the modification resulting from tial area of disturbance (Aid):disturbance of the Fish Creek site is much lessextensive than that at East Oumalik (Lawson and Si = Afd lAid (2)Brown 1979).

As a simple comparison of the physical effects The disturbed area is defined as an area initiallyof disturbances on the terrain of each site, I have affected by some disturbance (e.g. the area ofcomputed a severity index (S) of disturbance as tracks of a wheeled vehicle). The impacted area

25

'4A

70 92

60I

S50- 79-k40

O.lQ .>,,

20 /

20 1",0 ,/! /

-I 0 I 2 3 4 5 6 7 8

Phi Size

a.

80A 80.

17/

60-.

41 92

a-

~40- 79-1 /

20- 94 / /

-i 0 I 2 3 4 5 6

Phi Size

b.

Figure 23. Representative frequency curves (a) and cumulativecurves (b) of grain size distribution in samples of eolian sand atFish Creek. Frequency curves computed by numerical differenti-ation.

0

is an area that is physically modified in response nent and thus some recovery occurred to return

to the initial disturbance. the area to its previous condition.

Thus for 5, = 1.0, the impacted area equals In Table 2, values for S at Fish Creek and East

the area initially disturbed. For S. > 1.0, the im- Oumalik are compared for the four general

* pact of disturbance has spread beyond the area types of disturbances. Typical depths of depres-

physically disturbed. Values of S < 1.0 indicate sions are also listed. S values measured at East

that the effect of disturbance was not perma- Oumalik (0.9 to 2.6) were generally much larger

26

Distonce (meters) than those at Fish Creek (0.9 to 1.2). At both sites,(a) 0 20 40 60 so 1000 20 4 6 8 removal of vegetation and soil had the most se-

0 ---- -,,- vere impacts. The areal extent of impact usually4 ;' covers or extends beyond the boundaries of the

original disturbance on the East Oumalik site,8 whereas it is most often limited to within the in-

dividual areas actually disturbed at Fish Creek.Similarly, the depth of depressions and also theincrease in relief are much larger at East Ouma-

M(b) 0 20 40 60 so lik than Fish Creek.; 0 -, - Three factors appear to be the most important

- 0influences on the physical modifications of the

two sites: 1) spatial variability in ice volume,which directly affects the mode of degradation,2) physical properties of the sediments, which af-fect their susceptibility to failure once thaw be-gins and 3) the local and regional slope, which

(C) 0 20 40 60 80 affects moisture conditions, drainage and thus0 ... degradational processes.

-- -The importance of material properties is4 shown bV comparing the grain size, water con-

tent, dry density, void ratio and other engineer-8 ing properties of samples of disturbed and undis-

turbed sediments of Fish Creek and East Ouma-lik (Table 3). These data indicate that the sedi-

Figure 24. Stratigraphic cross sec- ments at East Oumalik were generally unstabletions of undisturbed (a) and dis- at thaw. In contrast, the sand at Fish Creek clear-turbed (bc) areas at Fish Creek. Pre- ly had significant frictional resistance to shear.sence of ground ice was defined by Water contents of the sand remain well belowdrilling at the locations identified the liquid limits and they are generally unsatur-on the cross sections. Uppermost ated. Similarly, the granularity and relativelydashed line in (b) and (c) represents high porosity of the material suggest that poreprofile of surface prior to distur- pressures will not significantly increase duringbance. Other symbols defined on thawing.Figure 13. Location shown in Figure Volumetrically, ice composed 35% more of22. the near-surface sediments (upper 5 m) at East

Table 2. General comparison of physical modifications toterrain at East Oumalik (EO) and Fish Creek (FC) drill sitesdue to disturbances listed by groups (Table 1). Si representsareal effects and is defined in the text.

Initial S Depth ofdisturbance Site (Severity index) depressions (m)

Group 1 EO 1.1 to 1.43 07 to 42FC 1.0 01 to 07

Group2 EO 09 to 11 01 to 11

FC 09 to 1.0 Up to0.2

Group 3 EQ 17 to 26 (1 to 5.5

FC 10 to 12 02 to 15

Group 4 EO 1.25 to 2.5 10 to 5.0FC 1.0 to1.2 04 to 20

27

Table 3. Selected properties of near-surface sediment from undisturbed and dis-

turbed locations at the East Oumalik and Fish Creek drill sites.

last Oumnalik Fish Creekupland upland

Undisturbed Disturbed Undisturbed Disturbed

Crain-sie M,) mean mn - S. So m - 5 50 mn - 2 75 m - 2.75(m), std dev (d1 6 -1 2 6 - 12 d6-07 d -07

Moisture content 80 to 250 40 to 120 19 to 71 22 to 28(% dry wt) (sporadically

to 120%)

Ice volume M%) 6t0 to it0) 40 to 65 231 to b8 33 to 42(excludes i e wedges) (mi - 85) (m - 47)

Degree of satuiration 0 95 to 1 2 08 to 1 1 t0 6 to 1 05 0 6 to 1.0)Oroen) (m - 1,05) (m - 0 9b)

Bulk density t09tol1 6 1.6 tol1 8 1 5 to 22 1.8 to2l1(Og/um) (m - 1 2) (m - 1 65) (m - 20t) (m - 2.0)

Dry density 0 1to 11l (8 to 12 1 4to 18 1 5to 1

Voidl ratio 31 to 14 0.5 to 2 8 0t4 to 1 61 04 toO0 78

Liquidity index 1 6 to >15 0 9 to 1,2 -1 to ( 5 -1 to 0 3

0M

Figure 25. Aerial photograph of area around concrete drill pad at Fish Creek-site. Melting of ice wedges hy surficial disturbances formed a polygonal

e pattern of thaw depressions. View wvest.

28

Oumalik than at Fish Creek. Also, massive small differences between the properties of un-- ground ice composed only an estimated 20 to disturbed seasonally frozen sediment and dis-

25% of the upper 5 m of the Fish Creek mater- turbed perennially frozen sediment (Table 3). Ofials, whereas it composed greater than 65% at particular importance, ice volume decreasedEast Oumalik. This difference results from the from a range of 40 to 65% in undisturbed frozensmaller size of ice wedges and absence of ice sands to a nearly uniform 38-42% in the season-lenses and layers at Fish Creek (Fig. 13, 24). ally frozen sands (Table 3). Such a change

The distribution and size of massive ground amounts to a maximum subsidence of only 0.2.ice limited the depth of thaw subsidence and al- to 1 m after thawing. The bulk density and ',oidtered expansion of degradation at Fish Creek. ratios of disturbed and undisturbed sands are al-The low volume of ground ice resulted in a more so not significantly different and indicate thatrapid buildup of an insulating layer of thawed consolidation has had minimal effect on the up-sediment. Maximum subsidence values are ap- land terrain.proximately equal to or less than the largest Climate may have been a factor in determin-depths of ice wedges. Because of the low relief, ing the difference in response of the two sitesdrainage of the central part of the site was also but it is, however, probably less important thanlimited and meltwater apparently ponded in the physical properties of the terrain and sedi-most thaw depressions. Even in areas modified ments. Climatic data for these sites are sparseby removal of the vegetative mat and soil at Fish and discontinuous, but the more coastal andCreek, depressions are limited in size and extent. northerly Fish Creek site apparently has a colderWedge ice was generally not encountered in climate than the inland East Oumalik site. Meandrilling beneath these areas in 1979 and 1980. annual air temperatures (MAT) predicted fromWedge ice remains beneath such areas at East mostly suinner temperature data for 1978 toOumalik, however, and dimensions of depres- 1980 indicate a MAT at Fish Creek of -11.6°Csions are several times larger. and at East Oumalik of -10.4 0 C (Haugen and

The fact that thaw depressions at Fish Creek Brown 1980, Haugen pers. comm.*). The thawform a polygonal pattern determined by the season is also generally warmer and longer atformer location of ice wedges (Fig. 25) is indica- East Oumalik so that depth of seasonal thaw istive of a much less active role by gravitational similarly larger. These conditions suggest that aslope processes in physically modifying the Fish disturbance might cause more rapid and possi-Creek site. Present relief in disturbed areas sug- bly deeper penetration of thaw at East Oumalik.gests that thaw depressions did not develop mar- Thus, following the initial disturbance, terrainginal slopes exceeding 1 m in height and probab- modifications at Fish Creek were mainly the re-ly most were 0.5 m or less. suit of thaw settlement and consolidation. The

This increase in relief during thaw subsidence apparent one-to-one relationship noted in the in-is insufficient to generate gravitational proces- tensity of disturbance in 1949 to active layerses of the type and extent that occurred at the thickness in 1978 at this site (Lawson et al. 1978)East Oumalik site. Lateral movement of thawed probal results from the inactivity of degrada-sand into subsiding areas at Fish Creek was tional processes other than thaw settlement.therefore limited probably to creep (especially Comparison of the two sites also suggests thatwhere the vegetation provided additional resis- the activity of degradational processes hadtance to movement), small slumps, and possibly probably diminished within 5 to 10 years aftergranular flow of dried sand. It basically resulted abandonment of the camp at Fish Creek and thatin a reduction in the angle of side slopes of thaw further physical changes since that time havedepressions, drainage ditches and bulldozed been minimal.trails to near the natural angle of repose of the Certain of the construction practices used insand. Similarly, thermal and hydraulic erosion at 1949 at Fish Creek and in 1950 at East Oumalik,Fish Creek were active only within drainage such as bulldozing trails and off-road vehicleditches and bulldozed trails located on the movement, are generally prohibited in northernslopes of the stream valley or drained lake permafrost regions or Alaska today. Gravel padsbasins. are now used beneath camps and drill rigs, but

Subsidence of the ground surface resulting the long-term effects of these pads are notfrom thawing and consolidation of the sand wasminimal at Fish Creek and is now reflected in *R Haugen, CRREL, pers. comm 1981

29

0

known Other techniques, including excavation Analyses of the East Oumalik site suggest thatdnd burning of trash, continue to be used (e.g. the degradational processes were most activeFrench 1980) This study suggests that excava- for perhaps 10 to 15 years following disturbancetions or burning of trash may cause extensive in 1950, with the level of activity and physicalthaw subsidence and other modifications to ter- modifications to the site decreasing since thatrain composed of ice-rich, fine-grained materials time to that of the present. Degradational pro-such as at East Oumalik, yet will cause much cesses remained active at several locations inless thaw subsidence with few other effects in and around the site in 1981. The thermal regimeice-poor, coarse-grained materials such as at Fish is apparently approaching equilibrium with theCreek. Thus, if such techniques are used, they modified physical condition of the site, but ad-should be sited, when possible, in ice-poor, thaw justments to the thickness of the active layer arestable terrain. probably continuing. Areas southwest of the ori-

ginal site that are undergoing thaw subsidenceare, however, not likely to show cessation of

DISCUSSION AND CONCLUSIONS physical changes for about 10 years.Comparison of the impacts at East Oumalik

Camp construction and occupation of the and Fish Creek, where activities that causedEast Oumalik upland in 1950 caused an exten- disturbance and length and seasons of occupa-sive modification of the terrain, drainage, annual tion were similar, indicates that the types ofdepth of thaw, surficial processes and properties degradational processes differed and that thisof near-surface materials. These modifications difference is directly related to the properties ofwere induced by changes in the thermal regime the perennially frozen sediments and terrain.caused by the various activities that took place Fish Creek was not affected as extensivelyon the site. Increased ground temperatures re- because the upland sand possessed strength insuited in subsidence as the ice-rich, perennially the thawed state and was not highly susceptiblefrozen silt of the upland thawed, which subse- to failure or to erosion by meltwater. The lowerquently initiated a suite of degradational proces- volume of ground ice and relief minimized bothses. These processes eroded and removed thermal and mechanical erosion by meltwaterthawed sediment and meltwater from thaw and the activity of gravitational slope processes.slopes and depressions. Thawing of undisturbed Most modifications of the Fish Creek uplandsilt next to subsiding areas led to its failure, mass were simply the result of thaw subsidence andmovement into the depressions and a lateral ex- consolidation.pansion of physical changes to the upland be- The contrast between these sites indicatesyond the area actually disturbed. Some undis- that geotechnical investigations of areas under-turbed areas next to the camp are now being lain by perennially frozen ground should includemodified, apparently as the result of this lateral detailed analysis of the in-situ conditions andmigration process testing of materials for response during thaw.

The primary factors of the near-surface mater- Determining the texture, ice volume, void ratio,ials and terrain that determined the extent of density, water content and liquid limit of themodification at East Oumalik are 1) ice content, sediment appears to indicate the potential sus-2) dimensions and distribution of ice wedges and ceptibility of perennially frozen sediments toother massive ice, 3) properties of the sediments long-term and extensive impacts after they areafter thawing, and 4) relief before disturbance, disturbed. Further, natural relief of the site com-

and as modified by thaw subsidence. Thawing of bined with changes in elevation and slope due tothe ice-rich silt produced a sediment with little thaw subsidence determine drainage and affector no strength that was highly susceptible to fail- the type and extent of degradational processesure and erosion. Natural relief on the site, com- that act upon the thawed sediment.bined with local increases in relief as thaw subsi-dence took place, were sufficient to cause fail- LITERATURE CITEDure in thawing slopes by gravitational processesand cause meltwater erosion of interconnected Abele, G., D.A. Walker, J. Brown, M.C. Brewerthaw depressions. Degradation subsided only af- and D.M. Atwood (1978) Effects of low ground

*ter thaw bulb expansion was minimized by re- pressure vehicle traffic on tundra at Lonely,duced availability of meltwater, increased sedi- Alaska. CRREL Special Report 78-16.mentation in thaw depressions, and changes in ADA061777slopes.

- 10

6

Adam, K.M. and H. Hernandez (1977) Snow and French, H.M. (1974) Active thermokarst proces-ice roads: Ability to support traffic and effects ses, eastern Banks Island, western Canadian Arc-on vegetation. Arctic, vol. 30, p. 13-27. tic. Canadian Journal of Earth Sciences, vol 11, p.Berg, R. and N. Smith (1976) Observations along 785-794.the pipeline haul road between Livengood and French, H.M. (1975) Man-induced thermokarst,the Yukon River. CRREL Special Report 76-11. Sachs Harbor airstrip, Banks Island, NorthwestADA026637. territories. Canadian Journal of Earth Sciences,Black, R.F. (1964) Gubik Formation of Quater- vol. 12, p. 132-144.nary age in northern Alaska. U.S. Geological Sur- French, H.M. (1980) Terrain, land use and wastevey Professional Paper 302-C. drilling fluid disposal problems, Arctic Canada.

Black, R.F. (1969) Thaw depressions and thaw Arctic, vol. 33, p. 794-806.

lakes: Biuletyn Peryglacjalny, vol. 19, p. 131-150. French, H.M., and P. Egglinton (1973) Thermo-

Bliss, L.C., 1970, Oil and ecology of the Arctic. karst development, Banks I.sland, Western Cana-

Transactions, Royal Society of Canada, 4th Ser- dian Arctic. In Permafrost: Second International

ies, vol. VII, p. 1-12. Conference, North American Contribution. Wash-Bliss, L.C. and R.W. Wein (1971) Changes to the ington, D.C.: National Academy of Sciences Pub-

active layer caused by surface disturbance. Pro- lication 2115, p. 203-212.ceedings of a Seminar on the Permafrost Active Grave, N.A. and I.A. Nekrasov (1962) Some ob-Laver, Ottawa: National Research Council of servations on thermokarst in the vicinity of theCanada Technical Memorandum 103, p. 37-46. settlement of Aadyr. Problems of the North, no.Brewer, M.C. (1958) Some results of geothermal 4, p. 165-172.investigations of permafrost in northern Alaska. Haugen, R.K. and 1. Brown (1980) Coastal-inlandTransactions, American Geophysical Union, vol. distributions of summer air temperature and pre-

39. p 19-26. cipitation in northern Alaska Arctic and AlpineBrown, I. (1965) Radiocarbon dating, Barrow, Research, vol. 12, p. 403-412Alaska. Arctic, vol. 18, p. 36-48. Heginbottom, J.A. (1971) Some effects of a forestBrown, J. (1967) Tundra soils formed over ice fire on the permafrost active layer at Inuvik.wedges, northern Alaska. Soil Science Society of N.W.T. Proceedings on the Permafrost ActiveAmerica, Proceedings, vol. 31, p. 686-691. Layer, National Research Council of Canada,Brown, I., W. Rickard, and D. Vietor (1969) The Technical Memorandum 103, p. 31-36.effect of disturbance on permafrost terrain. Heginbottom, J.A. (1973) Some effects of surfaceCRREL Special Report 138. AD699327. disturbance on the permafrost active layer at In-

Brown, 1. and N.A. Grave (1979) Physical and uvik, N.W.T. Government of Canada, Environ-thermal disturbance and protection of perma- mental-Social Committee on Northern Pipe-frost. Proceedings of the Third International Con- lines, Report. 73-16.ference on Permafrost, Edmonton, Alberta, Cana- Hernandez, H. (1973) Natural plant recoloniza-da, Ottawa: National Research Council of Can- tion of surficial disturbances, Tuktoyaktuk Pen-ada, vol. 2, p. 51-92. insula Region, N.W.T. Canadian Journal of Bo-Brown, R.J. (1963) Influence of vegetation on tany, vol. 51, p. 2177-2196.permafrost. In Permafrost: International Confer- How, G.T.S. (1974) Effects on the terrain of con-ence, Lafayette, Indiana, Washington, D.C.: Na- struction of the proposed Mackenzie gas pipe-tonal Academy of Sciences Publication 1287, p. line project. In Research Reports, Environmental20-25. Impact Assessment of Mackenzie Gas Pipeline,Carter, L.D. (1981) A Pleistocene sand sea on the Alaska to Alberta. Winnepeg, Manitoba: Environ-Alaskan Arctic Coastal Piain. Science, vol. 211, mental Protection Board, p. 10-27.

p 181-383. Isaacs, R.M. (1974) Geotechnical studies of per-

Crory, F.E. (1973) Settlement associated with the mafrost in the Fort Good Hope-Norman Wells

thawing of permafrost. in Permafrost: Second In- Region, N.W.T. Government of Canada, Environ-

ternational Conference, North American Contri- mental-Social Committee on Northern Pipe-

bution, Washington, D.C.: National Academy of lines, Report 74-16.S(iences Publication 2115, p. 599-607. Ives, I.D. (1970) Arctic tundra: How fragile? AFerrians, 0.1., R. Kachadoorian, and G.W. Greene geomorphologist's point of view. Transactions,(1969) Permafrost and related engineering prob- Royal Society of Canada, 4th series, vol VII, p.

lems in Alaska. U.S. Geological Survey Profes- 39-42.sional Paper 678.

31

Johnson, K.M. (1978) Map of slopes and selected Mackay, J.R. (1977) Changes in the active layergeomorphic features, NPRA. U.S. Geological from 1968 to 1976 as a result of the Inuvik fireSurvey, Open File Report 78-206. Report of activities, Part B3 Geological Survey ofKomlrkovi, V. and P.J. Webber (1980) Succession Canada, Paper, 77-1 1, p 27 ,-275.and recovery of old wells on the Alaskan North McRobert, E.C. (1978) Slope stability in cold re-Slope. In High-Altitude Revegetation Workshop gions. In Geotechnical Engineering for Cold Re-No. 4 (C.L. Jackson and M.A. Schuster, Eds.). Col- gions (O.B. Andersland and D M. Anderson,orado State University Information Series no. 42, Eds.). New York: McGraw-Hill, p. 16?-404p. 38-64. McRoberts, E.C. and N.R. Morgenstern (1974a)Kurfurst, P.J. (1973) Terrain disturbance suscepti- The stability of thawing slopes Canad, in Geo-bility, Norman Wells area, Mackenzie Valley. technical Journal, vol. 11, p. 447-469.Government of Canada, Environmental-Social McRoberts, E.C. and N.R. Morgenstern (1974b)Committee on Northern Pipelines Report 73-24. The stability of slopes in frozen soil, MackenzieLachenbruch, A.H. (1959) Periodic heat flow in a Valley, N.W.T. Canadian Geotechnical Journal,stratified medium with application to per- vol 11, p. 554-573.mafrost problems. U.S. Geological Survey McRoberts, E.C. and N.R. Morgenstern (1975JBulletin 1052. Pore water expulsion during freezing. CanadianLawson, D.E. (1979) Human-induced thermokarst Geotechnical Journal, vol. 12, p 130-141.processes at East Oumalik, northern Alaska. McRoberts, E.C., E.B. Fletcher and J.F. NixonGSA Abstracts with Program, Geological Society (1978) Thaw consolidation effects in degradingof America Annual Meeting, San Diego, vol. 11, p. permafrost. Proceedings, Third International463. Conference on Permafrost. Ottawa: National Re-Lawson, D.E. and B.E. Brockett (1980) Drilling search Council of Canada, vol. 1, p. 693-699.and coring of frozen ground in northern Alaska, Morgenstern, N.R. and I.F. Nixon (1971) One-di-spring 1979. CRREL Special Report 80-12. ADA mensional consolidation of thawing soils. Cana-084277. dian Geotechnical Journal, vol. 8, p. 558-565Lawson, D.E. and 1. Brown (1979) Human-induced Muller, S.W. (1947) Permafrost or Permanentlythermokarst at old drill sites in northern Alaska. Frozen Ground and Related Engineering Prob-The Northern Engineer, vol. 10, no. 3, p. 16-23. lems. Ann Arbor, Michigan: ).W Edwards, IncLawson, D.E., 1. Brown, K.R. Everett, A.W. John- Nixon, J.F. (1973) Thaw consolidation in someson, V. Komakov, B.M. Murray, D.M. Murray layered systems. Canadian Geotechnical journal,and P.J. Webber (1978) Tundra disturbances and vol. 10, p. 617-631.recovery following the 1949 exploratory drilling: Nixon, J.F. and E.C. McRoberts (1973) A study ofFish Creek, northern Alaska. CRREL Report some factors affecting the thawing of frozen78-28. ADA065192. soils. Canadian Geotechnical Journal, vol. 10, p.Linell, K.A. (1973) Long-term effects of vegeta- 439-452tive cover on permafrost stability in an area of Nixon, J.F. and B. Ladanyi (1978) Thaw consolida-discontinuous permafrost. In Permafrost: Second tion. In Geotechnical Engineering for Cold Re-International Conference, North American Con- gions (O.B. Andersland and D.M. Anderson,tribution. Washington, D.C.. National Academy Eds.). New York: McGraw-Hill, p. 164-215.

, Sciences Publication 2115, p. 688-693. Nixon, J.F. and A.j. Hanna (1979) The undrainedLivingstone, D.A., K. Bryan, Jr. and R.G. Leahy strength of some thawed permafrost soils. Cana-(1958) Effects of an arctic environment on the dian Geotechnical journal, vol. 16, p. 420-427.origin and development of freshwater lakes. Lim- Pollard, W.H. and H.M. French (1980) A first ap-nology and Oceanography, vol. 3, p. 192-214. proximation of the volume of ground ice,Mackay, J.R. (1970) Disturbances to the tundra Richards Island, Pleistocene MacKenzie Delta,and forest tundra environment of the western Northwest Territories, Canada. Canadian Geo-Arctic. Canadian Geotechnical Journal, vol. 7, p. technical Journal, vol. 17, p. 509-516.420-432. Radforth, J.R. (1973) Long term effects of sum-Mackay, j.R. and R.F. Black (1973) Origin, com- mer traffic by vehicles on tundra. Governmentposition and structure of frozen ground and of Canada, Environmental-Social Committee onground ice: A review. Permafrost: Second Inter- Northern Pipelines, Task Force on Northern Oilnational Conference, North American Contribu- Development, Report 73-22tion. Washington, D.C.: National Academy of Reed, J.C. (1958) Exploration of Naval PetroleumSciences Publication 2115, p. 185-192. Reserve No. 4 and adjacent areas, northern Alas-

32

ka. U.S. Geological Survey Professional Paper Viereck, L.A. (1982) Effects of fire and firelines301. on active layer thickness and soil temperaturesRickard, W.E. and J. Brown (1974) Effects of off- in interior Alaska. In The Roger I.E. Brown Memo-road vehicles on the tundra landscape. Environ- rial Volume, Proceedings, 4th Canadian Perma-mental Conservation, vol. 1, p. 55-62. frost Conference (H.M. French, Ed.). Ottawa: Na-Sellmann, P.V., J. Brown, R.I. Lewellen, H. tional Research Council of Canada, p. 123-135.McKim and C. Merry (1975) The classification Viereck, L.A. (1973) Wild fire in the taiga of Alas-and geomorphic implications of thaw lakes on ka. Quaternary Research, vol. 3, p. 465-495.the Arctic Coastal Plain, Alaska. CRREL Re- Viereck, L.A. and C.T. Dyrness, Eds. (1979) Eco-search Report 344. ADA021266. logical effects of the Wickersham Dome fireTedrow, J.C.F. (1969) Thaw lakes, sinks and soils near Fairbanks, Alaska. U.S. Forest Service, Paci-in northern Alaska. Biuletyn Peryglacjalny, vol. fic Northwest Forest and Range Experimental20, p. 337-344. Station, Portland, Oregon. General Technical Re-Terzaghi, K. (1950) Mechanism of landslides. In port PNW-90.Application of Geology to Engineering Practice, Wahrhaftig, C. (1965) Physiographic divisions ofBerkey Volume, Geological Society of America, Alaska. U.S. Geological Survey Professionalp. 83-123. Paper 482.Terzaghi, K. (1952) Permafrost. Journal of the Williams, J.R. and W.E. Yeend (1979) Deep thawBoston Society of Civil Engineers, vol. 39, no. 1, basins of the inner Arctic Coastal Plain, Alaska.p. 1-50. In The U.S. Geological Survey in Alaska, U.S.

* Terzaghi, K. and R. Peck (1967) Soil Mechanics in Geological Survey Circular 804-B, p. 1335-1337.Engineering Practice. New York: John Wiley and Williams, J.R., W.E. Yeend, L.D. Carter and T.D.Sons. Hamilton (1978) Preliminary surficial depositsU.S. Navy (1951) East Oumalik Test Well No. 1: map of National Petroleum Reserve-Alaska.Drilling, engineering and geological completion U.S. Geological Survey Open File Report 77-868.report. Naval Petroleum Reserve No. 4. Bureauof Yards and Docks, U.S. Geological Survey.

33

A facsimile catalog card in Library of Congress MARCformat is reproduced below.

Lawson, Danel E.Long-term modifications of perennially frozen sedi-

ment and terrain at East Oumalik, northern Alaska /by Daniel E. Lawson. Hanover, N.H.: Cold Regions Re-search and Engineering Laboratory; Springfield, Va.:available from National Technical Information Service,1982.vii, 42 p., illus.; 28 cm. ( CRREL Report 82-36. )Prepared for U.S. Geological Survey by Corps of

Engineers, U.S. Army Cold Regions Research and Engin-eering Laboratory.Bibliography: p. 30.1. Alaska. 2. Environmental impact. 3. Erosion.

4. Ground ice. 5. Ice wedges. 6. Permafrost.7. Soils. 8. Thermal degradation. 9. Thermokarst.10. Tundra. I. United States. Army. Corps of Engin-eers. II. Cold Regions Research and Engineering Lab-oratory, Hanover, N.H. III. Series: CRREL Report82-36.

.4