Lecture 1: Introduction

Geology - the study of the Earth, the processes that shape it, and the resources that could be obtained from

it.

Main branches

Physical Geology - deals with the materials that comprise the Earth and the processes that affect it (e.g.,

Volcanology, Seismology, Environmental Geology, Engineering Geology, Mining Geology, Petroleum Geology,

Mineralogy, Petrology, Geomorphology, Geophysics, Geochemistry, Planetary Geology)

Historical Geology - the study of the origin and evolution of the Earth through time (e.g., Paleontology,

Stratigraphy, Geochronology)

Basic Concepts

Catastrophism – proposed by Georges Cuvier; advocates the idea that sudden, worldwide catastrophes are

the agents of change that alter the physical features of the Earth over time and that the latter remains

unchanged in between these periods of upheavals; widely accepted by theologians in the early 1800s due to

similarity with Biblical events such as Noah’s Flood (James Ussher, mid-1600s)

Uniformitarianism - proposed by James Hutton (late 1700s, “The Father of Modern Geology”), modernized

by Charles Lyell (mid1800s); “The present is the key to the past”; advocates the idea that the Earth is

continuously modified by geologic processes that have always operated throughout time (at different rates),

and that by studying them we can understand how the Earth has evolved through time

Relevance to daily life

Everything we use comes from the Earth

Particularly in the form of natural resources provided through application of geologic knowledge.

Construction - cement, concrete and asphalt

Fuel, light and heat - oil, gas and coal

Water

Prediction and avoidance of hazards, earthquakes, floods, volcanoes, landslides, erosion.

Lecture 2: The Planet Earth

Cosmology: study of the universe and its origins and processes

Formation of the Universe: Big Bang Theory

Formation of the Solar System: Nebular Hypothesis

The Big Bang Theory: proposed by the Belgian priest Georges Lemaître in the 1920s ; contends that the

Universe originated from a cosmic explosion that hurled matter in all directions 15 and 20 billion years ago;

Edwin Hubble justified Lemaître’s theory through observations that the Universe is continuously expanding;

galaxies are moving away from each other

Evidence of Big Bang: red shift and cosmic background microwave radiation �metric expansion of space

Nebular Hypothesis: proposed by Emaneuel Swedenborg, Immanuel Kant and Pierre Simon de Laplace in the

18th century; the solar system originated from a single rotating cloud of gas and dust, starting 4.6 billion

years ago, which contracted due to gravity

1. The Big Bang produced enormous amount of matter: rotating cloud of gas and dust.

2. The rotating gas-dust cloud began to contract due to gravity. Most of the mass became

concentrated at the center, forming the Sun.

3. The remaining matter condensed to form the planets.

The Sun: a middle-aged star; mostly made up of hydrogen, the principal product of the Big Bang; sun’s

center became compressed enough to initiate nuclear reactions, consequently emitting light and energy (sun

became a star)

The Planets: composition depended on distance from the sun; planets nearest the sun contained high-temp

minerals (e.g. iron) while those that are far away contained lower-temp materials (e.g. methane and

ammonia, and some that contained water locked in their structures)

Mercury, Venus, Earth, Mars: inner or terrestrial planets (nearest the sun); rocky composition: largely

silicate rocks and metals (Si, Fe, O)

Jupiter, Saturn, Uranus, Neptune: giant or Jovian planets (outer planets; far from the sun); lack solid

surfaces: in gaseous or liquid form; composition: light elements (H, He, Ar, C, O, Ni)

The Earth: started as a “dust ball” from the nebular gas and dust brought together by gravity (accretion),

which was heated (heating) and eventually segregated into layers (differentiation) as it cooled; when cooling

set in, the denser elements (e.g., iron) sank while the lighter ones floated out into the surface, creating a

differentiated Earth

The Moon: said to have been formed by a Mars-sized impactor that collided the flanks of the Earth during its

early stages (not yet differentiated) removing a significant chunk of the still-molten Earth (Giant Impact

Hypothesis)

Earth’s Chemical Composition by mass: 34.6% Iron, 29.5% Oxygen, 15.2% Silicon, 12.7% Magnesium

Circumference was popularly computed by Eratosthenes

Shape: oblate spheroid

Equatorial Radius = 6378 km

Polar Radius = 6357 km

Equatorial Circumference = 40076 km

Polar Circumference = 40008 km

Volume = 260,000,000,000 cu. miles

Density = 5.52 g/cm3

Age: 4.6 billion years

Earth’s Large Scale Features

Continents (prominent features: mountains

mountains; mountain belts – mountain ranges that run across a vast area)

Ocean basins (prominent features: oceanic ridges; trenches; seamounts/guyots; abyssal hills/plains)

Internal Structure of the Earth

Geochemical layering: based on chemical composition of rocks

Geophysical layering: based on the physical characteristics of materials/rocks

Crust

1. Oceanic: basaltic composition (SiMa);

3 to 15 km thick; density: ~3.0 g/cm

2. Continental: granitic composition

(SiAl); 20 to 60 km thick; density: ~2.7

g/cm3

Mantle: extends to a depth of ~2900 km (Fe,

Mg)

1. Upper mantle – extends from the base

of the crust

2. Mesosphere – lower mantle; from 660

km depth to the core-mantle boundary

Core: iron-rich sphere with small amounts of Ni and other elements

1. Outer core – 2270 km thick; liquid

2. Inner core – solid sphere with a radius of

Discontinuities/boundaries: determined from the study of earthquakes

transmission of energy; passes through solid and liquid and S

of energy; passes through solid only)

1. Mohorovicic (Moho) discontinuity

2. Gutenberg discontinuity – core

3. Lehmann discontinuity – outer core

Mechanical layers: layers that move

1. Lithosphere

a. Upper crust – brittle; 4

b. Lower crust/uppermost mantle

2. Asthenosphere – weak sphere; beneath the lithosphere and within the upper mantle

3. Mesosphere – solid, rocky layer

Isostasy: from a Greek word meaning “same standing” (Clarence Dutton, 1889); basically concerned with the

buoyancy of the blocks of the Earth’s crust as they rest on the mantle; changes in the load over certain

(prominent features: mountains – elevated features of continents; mountain ranges

mountain ranges that run across a vast area)

nt features: oceanic ridges; trenches; seamounts/guyots; abyssal hills/plains)

based on chemical composition of rocks

based on the physical characteristics of materials/rocks

: basaltic composition (SiMa);

3 to 15 km thick; density: ~3.0 g/cm3

: granitic composition

(SiAl); 20 to 60 km thick; density: ~2.7

: extends to a depth of ~2900 km (Fe,

extends from the base

lower mantle; from 660

mantle boundary

rich sphere with small amounts of Ni and other elements

2270 km thick; liquid

solid sphere with a radius of 1216 km

: determined from the study of earthquakes (P-waves: primary waves; parallel

transmission of energy; passes through solid and liquid and S-waves: secondary waves; normal transmission

of energy; passes through solid only)

(Moho) discontinuity – crust – mantle

core – mantle

outer core – inner core

layers that move

brittle; 4-15 km depth

Lower crust/uppermost mantle – ductile; 15 to 100 or 200 km depth

weak sphere; beneath the lithosphere and within the upper mantle

solid, rocky layer

: from a Greek word meaning “same standing” (Clarence Dutton, 1889); basically concerned with the

buoyancy of the blocks of the Earth’s crust as they rest on the mantle; changes in the load over certain

elevated features of continents; mountain ranges – chains of

nt features: oceanic ridges; trenches; seamounts/guyots; abyssal hills/plains)

waves: primary waves; parallel

waves: secondary waves; normal transmission

ductile; 15 to 100 or 200 km depth

weak sphere; beneath the lithosphere and within the upper mantle

: from a Greek word meaning “same standing” (Clarence Dutton, 1889); basically concerned with the

buoyancy of the blocks of the Earth’s crust as they rest on the mantle; changes in the load over certain

regions causes the lithosphere to make adjustments until isostatic equilibrium (i.e., neither rising or sinking)

is reached

Pratt’s theory: regional scale; elevation is inversely proportional to density. Thus, the higher the mountain,

the lower is its density; that is, light rocks “float” higher.

Airy’s theory: regional scale; Mountains have “roots” which extend down into the mantle. Thus, elevation is

proportional to the depth of the underlying “root”.

Vening Meinesz’ Theory: local scale; a.k.a. flexure theory; lithosphere is flexible; redistributes loads by

bending, like in Hawaii

Isostatic rebound in Ferroscandian region, Canada and Utah

How old is the earth?

Cooling through conduction and radiation (Lord Kelvin, 1897): ~24 – 40 m.y.

Rate of delivery of salt to oceans (John Joly, 1901): ~90 – 100 m.y.

Thickness of total sedimentary record divided by average sedimentation rates (1910): ~1.6 b.y.

Amount of evolution of marine mollusks (Charles Lyell, 1800s): ~80 m.y. for the Cenozoic

Radioactivity (Henri Becquerel, 1896): ~500 m.y.

Radiometric dating: 4.5 – 4.6 b.y.

Oldest dated Earth rocks: 3.4 to 4.03 b.y.

Meteorites and moon rocks: ~4.5 b.y.

Lecture 3: The Restless Earth

Continental Drift Theory: introduced by Alfred L. Wegener in his book “The Origin of Continents and

Oceans” in 1915

Supercontinents: Vaalbara, Kenorland, Columbia/Nuna, Rodinia (1.1 Ga-750 Ma); Pangaea (Laurasia and

Gondwanaland) (300-200 Ma)

Evidence for Continental Drift Theory

1. “Jigsaw puzzle” fit: e.g. Africa and South America

2. Fossils: Lystrosaurus, Cynognathus, Mesosaurus and Glossopteris

3. Rock type and structural similarities: rocks found in one continent closely match (in age and type)

those rocks found in the matching continent, e.g. glacier tillites, coal deposits, evaporates, mountain

belts like Appalachians in east coast of North America and Western Europe and Cape Fold Belt in

South America and Africa

4. Paleoclimatic evidence

a. Glaciers in South America, Africa, India and Australia

b. Coal in Antarctica

Sea Floor Spreading Hypothesis: introduced by Harry Hess (1960s); ocean floor around 130Ma while

continental rocks 4.6Ga; new material formed at mid-oceanic ridges

Wilson Cycle: from John Tuzo Wilson; explains life of an oceanic basin from sea-floor spreading hypothesis

Paleomagnetism and Continental Drift: Magnetic minerals (e.g. magnetite) in rocks align themselves in the

direction of the existing magnetic field at the time they were formed; rocks formed at the same time =

record of magnetic field should be the same; Positions of ancient magnetic poles for continents do not

coincide, therefore continents moved!

Magnetic reversals: Earth’s true (geographic) north coincides with magnetic north (normal polarity) and

Earth’s true (geographic) north coincides with magnetic south (reversed polarity); due to periodic

fluctuations in the inner core

Continental drift + Sea floor spreading + Paleomagnetism > Plate Tectonics

Plate Tectonics: Unifying theory of geology; all geological features and processes are related; concepts were

drawn together in 1968; lithosphere is made up moderately rigid plates (may consist of oceanic or

continental lithosphere; 7 major plates + several smaller plates)

Plate Boundaries

1. Convergent Plate Boundary: “crashing”; places where plates crash into each other; destruction of

crust

a. Oceanic-continental: subduction of oceanic crust beneath continental crust, formation of

volcanic arcs, e.g. Andes (from Nazca plate under South American Plate) and trenches

b. Continental-continental: collision and deformation of continental crust, formation of

mountain belts and ranges, e.g. Everest (from Indian Plate - Eurasian Plate collision) and

Appalachians (from North American Plate – Eurasian Plate collision)

c. Oceanic-oceanic: subduction of faster and/or denser oceanic crust, formation of island arcs

and deeper trenches, e.g. e.g. Marianas Trench (from Pacific Plate subduction to Philippine

Sea Plate)

2. Divergent Plate Boundary: “pulling apart”; places where plates are being pulled away from each

other, forms mid-ocean ridges, e.g. Mid-Atlantic Ridge, rift basins, e.g. Great Rift Valley in Syria to

Mozambique (African Plate and Arabian Plate) and islands, e.g. Iceland (North American plate and

Eurasian Plate); creation of crust

3. Transform Plate Boundary: “sliding”; places where plates slide past each other, e.g. San Andreas

fault in North American and Pacific Plates

Plate Boundaries associated with volcanism and earthquakes

Driving Mechanism

Convection Currents: Hot materials rise, cold materials sink

1. Two-layer convection – separated at depth of 660 kilometers

2. Whole-mantle convection – entire 2900-km mantle

“Slab-pull”

Evidence

1. Hot-spots: provide a frame of reference for tracing

the direction of plate motion; relatively small, long-

lasting, and exceptionally hot regions which exist

below the plates; provide localized sources of high

heat energy (thermal plumes) to sustain volcanism,

e.g. Hawaii

2. Global Positioning System

Philippine Tectonics

1. Manila Trench

2. Negros Trench

3. Sulu Trench

4. Cotabato Trench

5. Philippine Trench

6. East Luzon Trough

7. Philippine Fault Zone

Plate Boundaries associated with volcanism and

earthquakes, even in the Philippines!

Lecture 4. Minerals

Naturally occurring

Inorganic

Homogeneous solid

Definite chemical composition

Ordered internal structure

Mineraloid: naturally occurring, inorganic material that is amorphous (ex. glass, opal)

Polymorphism: ability of a specific chemical substance to crystallize in more than one configuration, which is

dependent upon changes in temperature, pressure, or both (ex. FeS2: pyrite and marcasite, graphite and

diamond)

Physical Characteristics of Minerals

Color: caused by the absorption, or lack of absorption, of various wavelengths of light

Streak: the color of a mineral in powdered form; not always identical to the color

Hardness: resistance of mineral to abrasion or scratching

Mohs’ Scale of Hardness

1. Talc

2. Gypsum

2.5. Fingernail

3. Calcite

3.5. Copper coin

4. Fluorite

5. Apatite, Steel Nail

5.5. Glass

6. Orthoclase

6.5. Streak Plate

7. Quartz

8. Topaz

9. Corundum

10. Diamond

Crystal Form: the shapes and aggregates that a certain mineral is likely to form

Cleavage: the tendency of a mineral to break in particular directions due to zones of weakness in the crystal

structure

Fractures or irregular breakages occur when bond strengths in a crystal structure is equal in all directions.

Luster: the ability of minerals to reflect light

Specific Gravity: Ratio of volume of a substance and the weight of the same volume of water

Other properties:

1. Magnetism – ex. magnetite

2. Fluorescence – ex. fluorite

3. Reaction to acid – ex. calcite

4. Taste – ex. halite, borax

5. Odor – ex. sulphur

6. Feel – ex. graphite, talc

Classification of minerals: Silicates and non-silicates

Bases of classification

Composition:

1. Single element (e.g. Cu, Au, S)

2. 2 elements (e.g. halite, pyrite)

3. Greater number of different kinds of atoms (e.g. KAl3Si3O10(OH)2)

Crystal Structure

The Silicates: largest group of minerals; compounds containing silicon and oxygen; building block: silicon

tetrahedron (SiO4)-4

Silicate

Group

Silicate

Structure Mineral Group Cleavage Example Associated rock

Nesosilicate "island" Olivine Group none olivine ferromagnesian

rocks

Inosilicate "single-

chain" Pyroxene Group

2 directions

at 90

degrees

pyroxene ferromagnesian

rocks

"double-

chain"

Amphibole

Group

2 directions

at 60-120

degrees

amphibole

mostly

ferromagnesian

rocks

Phyllosilicate "sheet" Mica Group 1 direction

biotite,

muscovite,

clay

minerals

felsic rocks

Tectosilicate "3D

network" Feldspar Group

2 directions

at 90

degrees

plagioclase

feldspar,

orthoclase

feldspar

both

ferromagnesian

and felsic rocks

Quartz Group no cleavage quartz felsic rocks

Sorosilicate "sister" Epidote Group 1 direction epidote metamorphic

rocks

Cyclosilicate "ring" Beryl Group no cleavage emerald,

aquamarine

metamorphic

rocks

The Non-silicates

Mineral Group Characteristics Examples

Native Elements Single elements Gold (Au), Diamond (C), Silver (Ag)

Oxides Metallic ion and oxygen Hematite (Fe2O3), Magnetite (Fe3O4)

Sulfides Sulfur and a metallic ion Galena (PbS), Realgar (AsS)

Sulfates Metallic ion, sulfur & oxygen Barite (BaSO4), Gypsum (CaSO4)

Carbonates Metallic ion and carbon and

oxygen (CO3) Calcite (CaCO3), Rhodocrosite (MnCO3)

Phosphates Metallic ion and phosphate

and oxygen (PO4) Apatite (Ca5(PO4)3(F,Cl,OH))

Halides Metallic ion and a halogen (F,

Cl, Br, I and At) Halite (NaCl), Fluorite (CaF2)

Common rock-forming minerals: Feldspar, Quartz, Olivine, Pyroxene, Amphibole, Mica (Biotite and

Muscovite), Clay, Calcite

Non-renewable resource – processes that create the resources are so slow (takes millions of years to

accumulate)

Ores – useful metallic (and some nonmetallic) minerals that can be extracted and which contain useful

substances

Economic Importance:

1. Mineral resources – sources of metals and other materials

2. Gemstones

Gold and copper associated with volcanism in the Philippines.

Lecture 5: Igneous Rocks

The Rock Cycle

Rocks: naturally-occurring aggregate of minerals,

mineraloids, organic components and rock

fragments; classification based on mineral, texture

and formational processes

Common rock-forming minerals

• quartz: glassy-looking, transparent or translucent mineral which varies in colour from white and grey to

smoky; hard (H=7), durable and no cleavage; most common mineral on the Earth’s crust

• potassium feldspar (orthoclase): generally dull to opaque with a porcelain-like appearance; color varies

from red, pink, white and buff gray; all have 2 cleavages at approximately 90° and a hardness of 6; occurs

in well shaped prismatic and tabular crystals, which are sometimes striated

• plagioclase feldspar: may have striations (very fine "razor-cut" grooves on selected cleavage faces), but

not always; color varies from green, gray, white; all have 2 cleavages at approximately 90° and a

hardness of 6; crystals are usually flat and bladed, and commonly in compact groupings

• muscovite: most common of the mica minerals; typically found as massively crystalline colorless, white,

pearly material in "books”; has the characteristic of peeling into many thin flat smooth sheets or flakes;

has a 1 direction perfect cleavage

• biotite: crystals are in thick flakes; similar to muscovite but in darker in color

• amphibole: mostly black, forms long, slender crystals with 2 cleavages at 60° and 120°; most common

member: hornblende

• pyroxene: usually dark-green or black minerals with hardness of 5 or 6 and two good cleavages at right

angles (square cleavages)

• olivine: olive green to black, translucent, with a conchoidal fracture, sugar-like appearance

• calcite: a very common mineral in sedimentary rocks; commonly white to grey, sometimes clear and

transparent; hardness = 3

• clay minerals: very fine grained and difficult to tell apart in the field; vary in colour from white to grey,

brown, red, dark green and black

Igneous rocks formed from solidification of magma (intrusive) or lava which flows out from depths

(extrusive)

Magma: Molten material which may contain suspended crystals and dissolved volatiles (gases, such as water

vapor, CO2, SO2); composed of mobile ions of the 8 most abundant elements in the Earth’s crust: Si, O, Al, K,

Ca, Na, Fe, Mg

Formation of magma: Increase temperature, decrease pressure, add volatiles (i.e. water, carbon dioxide,

etc.)

Sources of heat

• original heat of the earth at the time of formation

• heat produced from radioactive decay

• heat transfer by conduction from a nearby body of magma

• hot mantle plumes

• frictional heat caused by rocks grinding past each other

Magma forms at Mid-Oceanic Ridges (MOR), Subduction Zones, Hot spots

Classification based on:

Silica content - amount of SiO2

Viscosity - resistance to flow

Temperature - temperature of melt formation

Basaltic magma

• High density

• Low viscosity

• Relatively low silica content

• “Dry”

• Crystallizes at high temperatures (~1000 -

1200ºC)

Granitic magma

• Low density

• High viscosity

• Relatively high silica content

• Gaseous

• Crystallizes at ~600°C

Kinds of igneous rocks

• Extrusive (volcanic) – molten rock solidified at the surface (ex., basalt, andesite, rhyolite)

• Intrusive (plutonic) – igneous rocks formed at depth (ex., gabbro, diorite, granite)

Intrusive Igneous bodies

• Stock – small discordant pluton

• Batholith – more than 100 sq. km. in

outcrop area

• Dike – tabular body cutting across

bedding (=discordant)

• Sill – concordant (= parallel to beds)

tabular body

• Laccolith – blister-shaped sill

• Lopolith – bowl-shaped sill

Textures

• Aphanitic – very fine-grained (<2mm

in diameter) as a result of rapid

cooling at the surface; minerals too

small to be seen by the naked eye

• Phaneritic – coarse-grained (>5 mm)

mineral sizes due to slow magma

cooling at depth.

• Porphyritic – very large crystals

(phenocrysts) embedded in smaller

crystals (groundmass)

• Vesicular – contains tiny holes called

vesicles which formed due to gas

bubbles in the lava or magma

• Glassy – molten rock quenched quickly as it was ejected into the atmosphere or contact with water.

• Pegmatitic – interlocking crystals greater than 1 cm

• Pyroclastic – formed when volcanic materials are extruded violently.

Pyroclastic Rock Identification (based on dominant fragment size)

• Ash – <2 mm in diameter

• Lapilli – 2-64 mm in diameter

• Block or bomb – >64 mm; block is extruded in a solid state (thus angular)while bomb is partially or

wholly molten (thus rounded or spiniform [football-shaped])

Cooling history based on crystal face geometry

• Euhedral – well-defined crystal faces

• Subhedral – intermediate faces

• Anhedral – no well-formed crystal faces

*suggests rate of cooling undergone by the magma (longer cooling period, more well-formed crystal faces)

Classification of Igneous Rocks based on mineral assemblage and other characteristics

Source of magma

Partial melting of mantle

Variation in magma composition due to:

• Assimilation: melting of overlying rocks and incorporation of melted rock material

• Magmatic differentiation, including:

• Fractional Crystallization

• Differential Settling: lighter minerals float, denser minerals sink

• Magma mixing: mixing of at least two chemically distinct melts

Classification (based chemical composition)

Felsic, Silicic or acidic: >63% SiO2

• Intermediate: 52-63% SiO2

• Mafic or basic: 45-52% SiO2

• Ultramafic or ultrabasic: <45% SiO

Viscosity

• ↑ temperature, ↓ viscosity

• ↑ SiO2, ↑ viscosity

• ↑ dissolved H2O, ↓ viscosity

Density

• heavier oceanic crust � mafic rocks

• lighter continental crust � felsic rocks

Lecture 6: Volcanism

Volcano: place on the Earth's surface (or any other planet's or moon's surface) where molten rock, gases and

pyroclastic debris erupt through the earth's crust

Eruption due to decompression (magma is lighter than surrounding rock)

Types of volcanoes

• Cinder Cones: relatively small (<300 m high); steep slopes (30

• Composite Volcanoes: layered structure (tephra and lava flows)

• Shield Volcanoes: slopes are gentle (15

ground; made up of successive lava flows

• Lava Domes: formed by relatively small, bulbous masses of lava too viscous to flow any great

distance; consequently, on extrusion, the lava piles over and around its vent

Rocks based on mineral assemblage and other characteristics

Variation in magma composition due to:

: melting of overlying rocks and incorporation of melted rock material

including:

Fractional Crystallization: minerals have different crystallization temperatures

: lighter minerals float, denser minerals sink

: mixing of at least two chemically distinct melts

composition)

<45% SiO2

↓ viscosity

mafic rocks

felsic rocks

: place on the Earth's surface (or any other planet's or moon's surface) where molten rock, gases and

pyroclastic debris erupt through the earth's crust

(magma is lighter than surrounding rock)

relatively small (<300 m high); steep slopes (30 – 40o); made up of pyroclastic material

layered structure (tephra and lava flows)

slopes are gentle (15o or less); shape resembles a Roman shield

ground; made up of successive lava flows

formed by relatively small, bulbous masses of lava too viscous to flow any great

extrusion, the lava piles over and around its vent

Rocks based on mineral assemblage and other characteristics

: melting of overlying rocks and incorporation of melted rock material

: minerals have different crystallization temperatures

: place on the Earth's surface (or any other planet's or moon's surface) where molten rock, gases and

); made up of pyroclastic material

shield lying on the

formed by relatively small, bulbous masses of lava too viscous to flow any great

Distribution of volcanoes

• Pacific Ring of Fire

• Hot spots

• Spreading centers

Volcanic Eruption Styles

Volcanic Explosivity Index or VEI - based on a number of things (e.g. plume height, volume, etc.) that can be

observed during an eruption

• Magmatic eruption: purely magmatic eruption, lavas and pyroclastic material only

• Hawaiian: calm eruptions where lava flows

• Strombolian: short-lived, explosive outbursts of pasty lava ejected a few tens or hundreds of

meters into the air

• Vulcanian: occur as a series of discrete, cannon-like explosions that are short-lived

• Pelean: mainly pyroclastic with nuee ardente (“glowing cloud”; hot glowing ash avalanche)

• Plinian: generate sustained eruptive columns; very destructive (Ultra-Plinian)

• Phreatomagmatic eruption: generated by the intereaction of magma with either groundwater or

surface water

• Surtseyan: volcanic eruptions that have come into contact with encroaching seawater

• Submarine: underwater eruptions

• Subglacial: under glaciers

• Phreatic eruption: steam and some rock fragments only, lava is unusual

Monitoring Volcanic Activity

• Remote Sensing

• Ground Deformation

• Seismicity

• Geophysical Measurements

• Gas

• Hydrology

Volcanic Hazard

Pyroclastic Flows: explosive eruptive phenomenon of fluidized masses of rock fragments and gases; gravity-

driven, which means that they flow down slopes.

Lahar: specific kind of mudflow made up of volcanic debris, remobilized pyroclastic deposits; can cause

fatalities years after an actual eruption

Volcanic Gases: can be directly harmful to humans, animals, plants, agricultural crops, and property (e.g.

CO2, SO2, HCl, H2S, F2, HF, etc.)

Lava Flow

Tephra: ejected material such as rock fragments

Benefits

Fertile lands

New islands

Pumice can be used as an abrasive

Porous volcanic rock can create fresh water aquifers

Tourism

Weather balance

Source of geothermal energy – benign source of electricity

Resources

• metallic resources, such as gold, copper, silver, platinum

o hydrothermal solution precipitates

• construction/ building materials

• tiles and countertops

• gravestones

• abrasive materials (for cosmetics)

• minerals