Geologic Time

Super what??!?!

Superposition: Younger rock layers are on top of older rock layers.

Used with the other principles of stratigraphy to study rock layers and layering.Stratigraphy : “Branch of geology concerned with the

study of the formation, composition, ordering in time, and arrangement in space of stratified rocks.” – USGS

Nicolaus Steno (1669)

http://stloe.most.go.th/html/lo_index/LOcanada8/801/2_en.htm

Principles of Stratigraphy superposition - in a vertical sequence of sedimentary or

volcanic rocks, a higher rock unit is younger than a lower one. "Down" is older, "up" is younger. 

horizontality - rock layers were originally deposited close to horizontal. 

Original lateral extension - A rock unit continues laterally unless there is a structure or change to prevent its extension. 

cross-cutting relationships - a structure that cuts another is younger than the structure that is cut. 

inclusion - a structure that is included in another is older than the including structure. 

"uniformitarianism" - processes operating in the past were constrained by the same "laws of physics" as operate today

http://www.talkorigins.org/faqs/dating.html :

Inclusion

Original lat. Ext.Cross

Cutting

Animations

Disconformity : http://duedall.fit.edu/wholeearth/PHysical%20geology%20animations/0012.swf

Geologic historyhttp://www.wwnorton.com/college/geo/earth2/content/chapter_12/animations.asp#12_1

Rock Layer Formation

Sedimentary: igneous rock that is broken down by weathering into fine particles. Compressed over time by it’s own weight and weight of layers above

Rock Layer Formation

Igneous: formed from liquid hot magma that cools above or below the earths surface.

Were are fossils found

Sedimentary rock -- yes, Most fossils are found in sedimentary rocks as an animal dies it get’s buried by sediment , perhaps along a river or lake bed, and the organic parts of the animal are replaced by minerals in the water/sediment that

Igneous rock -- nope, Fossils aren’t found in igneous rock because remember that igneous rock starts out as molten lava and if an animal were to be covered by it then it would melt or burn away.

How old are fossils? 2 Generic Methods:

Absolute ○ Several methods. ○ (radiometric) Measurement of the decay rate

of isotopes.Carbon 14 : 5730 years Dates organic materialPotassium – Argon : 50,000 to 2 billion years ago

Dates volcanic material

Relative○ Uses igneous rock above or below

sedimentary rock to determine age.

Which layers are Sedimentary/Igneous? S: 1,2,3,4,5,7,8,11,12 I: 10,8,6

Which layers are older? 1 - 12

What is a possible history for this area? 1-5 area was covered by an

ocean 7 - Oceans recede, area

appears to be covered by large amounts of plant life

9 small to mid size animals appear

11,12 larger animals appears

Resources http://www.usgs.gov/ http://jersey.uoregon.edu/~mstrick/AskGeoMan/geoQuerry13.ht

ml Wiki Sedimentary --

http://en.wikipedia.org/wiki/Sedimentary_rock http://www.talkorigins.org/faqs/dating.html http://www.pbs.org/wgbh/evolution/library/03/3/l_033_01.html http://pubs.usgs.gov/gip/geotime/time.html <- curvy geotime http://www.kidsgeo.com/geology-for-kids/0030-geologic-

time.php http://stloe.most.go.th/html/lo_index/LOcanada8/801/3_en.htm

“Geology an introduction to physical geology” , Chernicoff & Whitney, ISBN 0-13-147464-1 , Page 20

“Geology an introduction to physical geology” , Chernicoff & Whitney, ISBN 0-13-147464-1 , Page 234