Geology Exam Ii

Front 1

mineral vs. rock

Back 1

rocks made up of more than one mineral while a mineral is an entity itself

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3 types of rocks

Back 2

igneous, sedimentary, metamorphic

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Igneous Rocks

Back 3

formed by the solidification of molten rock
process known as crystallization as molten cools
form from melting of rocks in deep crust and upper mantle
make up most of the Earth
rocks melt b/c of earth's internal heat engine (accretion of planetisimals, heat-producing impacts, radioactivity)

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Magma

Back 4

melted rock in subsurface

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Lava

Back 5

melted rock above the Earth's surface (what comes out of volcanoes)

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extrusive rock

Back 6

also known as volcanic rock
form from lava cooling above the Earth's surface
faster cooling rate --> smaller crystals (fine-grained igneous rock)
i.e. basalt

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intrusive rock

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also known as plutonic rock
form from magma cooling just below the Earth's surface
slower cooling rate (hotter in the Earth than on surface) --> larger crystals (course-grained igneous rock)
i.e. granite

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glass

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opposite of crystalline
magma cools so fast that there are no crystals/crystalline structure

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Magma is made of:

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Silicon + Oxygen = silicon-oxygen tetrahedron
Aluminum
Calcium
Magnesium
Sodium
Potassium
Iron

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Volatiles in wet magma (15% of composition)

Back 10

Water
Carbon Dioxide
sulfur dioxide
nitrogen
hydrogen

Front 11

water is __% of gas erupted from volcano

Back 11

50%

Front 12

carbon dioxide is __% of gas erupted from volcano

Back 12

20%

Front 13

Commons minerals of igneous rocks

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SILICATES (b/c it's abundant and they melt at temps and pressures reach in lower parts of crust & mantle):
Pyroxene
Amphibole
Mica
Feldspar
Olivine
Quartz

Front 14

How igneous rocks differ from each other

Back 14

1.) Texture
2.) Silican Content
3.) Relative proportions of silicate materials

Front 15

How igneous rocks differ with respect to texture

Back 15

Depends on cooling rate:
Volcanic rocks - fine-grained (rapid cooling)
Plutonic rocks - course-grained (slow cooling)
i.e. pegmatite - VERY course-grained

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How igneous rocks differ with respect to silica content

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1. Felsic - 70% Silica; little Mg and Fe; coolest; most viscous
2. Intermediate - 55% silica
3. Mafic - 50% silica; rich in Mg and Fe
4. Ultramafic - 40% silica; more Mg and Fe; hottest; least viscous

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Melt viscosity

Back 17

hotter magma --> less viscous more volatiles --> less viscous
less silica --> less viscous

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2 eruption styles

Back 18

1.) Effusive
2.) Explosive

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Effusive eruptions

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Mafic
Volcanic deposits = Basaltic LAVA
Basaltic lava - darker in color, higher temp (1000-1200 deg C)
Quiet, slow, less viscous, lower silica content
i.e. Hawaiian volcanoes

Front 20

Types of lava in effusive eruptions

Back 20

Flood Basalts
Pahoehoe
Aa
Pillow Lava

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volcanoes

Back 21

planetary thermal-regulation system
site at which material reaches the surface of a planet from the interior
heat flow from temperature gradient

Front 22

volcanism

Back 22

molten rock rises buoyantly to the surface becasue it is less dense than surrounding rock

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Heat transfer modes

Back 23

1.) conduction
2.) convection
3.) advection (volcanoes)

Front 24

Flood Basalts (effusive)

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laval oozes out of fractures in earth's surface
last for millions of yrs
spread out in thin sheets that often pile up into basaltic lava plateaus
i.e. Great Columbian Plateau of Oregon and Washington

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Pahoehoe (effusive)

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congealed skin of lava cools, lava underneath still moving, twists and drags skin into coils
i.e. Mauna Loa Volcano, Hawaii

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Aa (effusive)

Back 26

lava moves slower, thicker skin forms, molten liquid still moves underneath and breaks thick skin into jagged blocks

Front 27

Pillow lavas (effusive)

Back 27

forms from underwater eruption
sacklike, ellipsoidal blocks

Front 28

Explosive Eruptions

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Felsic lava
pyroclastic deposits & rhyolitic lava & andesitic lavas
more viscous, rich in volatiles under high pressure
i.e. Western volcanoes

Front 29

Classification of pyroclasts

Back 29

Volcanic Ash --> fall and combine to form volcanic tuff
Volcanic bombs --> fall and combine to form volcanic breccia

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Obsidian

Back 30

pyroclastic deposit from explosive eruptions
"volcanic glass"
very Felsic
typically black in color (rich in Mg and Fe)

Front 31

Pumice

Back 31

pyroclastic deposit from explosive eruptions
light b/c of porous space

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Rhyolitic Lavas

Back 32

light in color
most felsic lava
erupts at temp of 800-1000 deg C
moves MUCH slower than basaltic lava

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Andesitic Lavas

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lava of explosive eruptions
intermediate silica content
properties that fall b/t basaltic and rhyolitic lavas

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Basalts (basaltic rock from basaltic lava - effusive eruptions)

Back 34

whole ocean floor made of basalts (i.e. pillow lava)
most abundant rock on Earth
volcanic islands made of basalt
oceanic & continental plateaus made of basalt

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2 eruptive styles

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1.) Central eruptions
2.) Fissure eruptions

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Central Eruptions

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1.) Shield volcanoes - effusive
2.) Volcanic dome - explosive
3.) Cinder-Cone - explosive
4.) Composite - explosive

Front 37

Shield Volcano

Back 37

broad, gently sloping cone
mafic lava (effusive eruptions)
i.e. Mauna Loa, Hawaii

Front 38

Volcanic Dome

Back 38

as though lava squeed out of vent like toothpaste; very little spreading
felsic lava (explosive eruption)

Front 39

Cinder-Cone Volcano

Back 39

vents discharge ONLY pyroclasts, no liquid
felsic lava (explosive)
i.e. Paricutin and Cerro Negro

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Composite Volcano

Back 40

= stratovolcano
emit lava as well as pyroclasts
steep-sided symmetrical cone
felsic lava (explosive)

Front 41

Fissure eruptions

Back 41

Basaltic lava flows out of cracks in Earth's surface
Flood basalts
Mafic lava (effusive)
i.e. Siberia and India

Front 42

Pyroclastic flow

Back 42

volcanic hazard
deposits of hot ash, dust and gases are ejected in a cloud that can eventually not support itself --> collapses and rolls down side of volcano and scorches everything in its path
can change climate by blocking out sun (i.e. Phillipines 1995)

Front 43

Crater

Back 43

bowl-shaped pit found at summit of most volcanoes, centered at vent
called a "lake" when it's filled with water

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Caldera

Back 44

large, steep-walled, basin-shaped depression
much larger than craters
resurgent - eruption, collapse, resurgence, eruption, ....
i.e. Yellowstone Caldera & Long Valley Caldera

Front 45

Phreatic Explosions

Back 45

volcanic hazard
steam explosions underwater caused when hot, gas-charged magma encounters ground water/sea water and generates steam --> explosion
i.e. Krakatoa, Indonesia

Front 46

Diatremes

Back 46

liquid comes from deep inside the Earth, unlike volcanoes whose lava comes from close to Earth's surface
vent and feeder channel left filled with breccia
i.e. Shiprock, NM

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Lahars

Back 47

torrential mudflows of wet volcanic debris caused when snow melts as volcano heats up --> flows down, picks up mud, rocks, debris along the way to create a thick slurry

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Edifice Collapses

Back 48

big piece of a summit breaks off, slides downhill in destructive landslide
perhaps caused by earthquake

Front 49

Volcanic Gases

Back 49

Water vapor (70-95%)
carbon dioxide
sulfur dioxide
traces of nitrogen
hydrogen
carbon monoxide
sulfur
chlorine

Front 50

fumaroles

Back 50

vents through which volcanoes continue to emit gas fumes and steam after a major eruption

Front 51

geyser

Back 51

hot-water fountain that spouts intermittently w/ great force;
circulating groundwater is heated by magma inside Earth;
water heats up --> less dense --> rises up --> fills chambers along path with steam & hot water --> high pressure --> released through explosion of water

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Grand prismatic (in hot springs)

Back 52

different colors around hot spring due to different bacteria living in different parts of the spring

Front 53

Western Volcanoes

Back 53

Baker
Glacier Pk
Rainier
St. Helens - most eruptions
Adams
Hood
Jefferson
Three Sisters
Newberry
Crater Lake
Medicine Lake
Shasta
Lassen

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Weathering

Back 54

general process by which rocks are broken down at Earth's surface, product STAYS in place

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Erosion

Back 55

set of processes that loosen and MOVE soil and rock downhill or downwind

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Importance of weathering and erosion:

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1.) produce clays, which make soil fertile
2.) produce soils
3.) produce dissolved substances that are carried by rivers to the ocean, which provide sustenance for ocean creatures

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Factors that control the weathering of rocks:

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1.) properties of parent rock
2.) climate ***
3.) presence or absence of soil - rock covered in soil will weather faster
4.) length of exposure

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2 kinds of weathering:

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1.) Chemical weathering
2.) Physical Weathering

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Chemical weathering

Back 59

chemical rxns that alter/destroy material (esp in warm, wet conditions - tropical climate)
Rxns:
1.) Dissolution
2.) Hydrolysis
3.) Oxidation
4.) Hydration
5.) Chemical weathering produced by organisms

Front 60

Dissolution (chemical weathering)

Back 60

dissolves the rock
carbon dioxide (atmosphere) + water (rain) = carbonic acid (acid rain)
calcite (what many rocks are made of) + carbonic acid = ions that dissolve in water --> thereby dissolving the rock
i.e. marble and limestone

Front 61

Hydrolysis (chemical weathering)

Back 61

water chemically reacts with (not dissolve) rocks and breaks them down - changes elements, chemical properties
chemical weathering of potassium feldspar: feldspar + carbonic acid + water = kaolinite (clay) + silica (dissolved) + potassium (dissolved) + bicarbonate ion (dissolved)

***like brewing coffee***

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Chemical effects of chemical weathering on silicates:

Back 62

1.) leaches cations and silica
2.) hydrates minerals
3.) makes the solutions less acidic

Front 63

Oxidation (chemical weathering)

Back 63

rock or minerals react with oxygen
olivine, pyroxene, amphibole - iron minerals present in rocks
iron and oxygen react to form iron oxide (rust)
rust = hematite (brown)
geothite = even more oxidation (yellow)
iron pyroxene + oxygen = hematite + silica (dissolved)

Front 64

Granite made of

Back 64

Quartz
Feldspar
Mica
Biotite
Amphibole

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Hydration (chemical weathering)

Back 65

absorption of water into crystal structure of minerals --> expands and breaks apart

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Chemical weathering produced by organisms

Back 66

microbes extract elements from rock for food --> destroys/decomposes rock
other microbes indirectly weather by acting as catalysts for other weathering processes

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Stability of minerals from fastest weathering, least stable to slowest weathering, most stable

Back 67

Halite
Calcite
Olivine
Ca-plagioclase
Pyroxene
Amphibole
Na-plagioclase
Biotite
Orthoclase
Quartz
Gibbsite
Hematite

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Physical weathering

Back 68

1.) natural zones of weakness
2.) exfoliation and spheroidal weathering
3.) root wedging
4.) frost wedging
5.) salt wedging
6.) differential thermal expansion of minerals creats stress in rocks (in deserts)
7.) other forces: rivers, glaciers, waves, burrowing creatures, humans

Front 69

Soils

Back 69

byproduct of weathering and erosion;
consists of rock and sediment that has been modified by physical and chemical rxns with organic material and rainwater to produce a substrate is fertile
1.) residual soil
2.) trasnported soil

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bedrock

Back 70

unaltered rock of any kind

Front 71

regolith

Back 71

any kind of unconsolidated debris that covers bedrock
*soil is one type of regolith

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residual soil

Back 72

formed directly from underlying bedrock

Front 73

transported soil

Back 73

forms from sedient that has been carried in from elsewhere (by rivers, glaciers, or wind)

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soil composed of:

Back 74

1.) fragments of bedrock
2.) clay minerals formed by the alteration of bedrock minerals
3.) organic matter produced by organisms that live in it

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3 processes that take place below Earth's surface that contribute to soil formation:

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1.) animals, plants, microbes and fungi interact with sediment - absorb nutrients, leave behind waste
2.) rainwater enters sediments and percolates downward: zone of leaching and zone of accumulation
3.) burrowing organisms churn soil

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zone of leaching

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O- to A-horizons
closer to surface where water dissolved ions and picks up find clay

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zone of accumulation

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B-horizon
further down from surface where new minerals precipitate out of water and it leaves behind the fine clay

Front 78

Idealized soil profile (temperate climate)

Back 78

O-horizon
A1-horizon
A2-horizon
B-horizon
C-horizon

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O-horizon

Back 79

mostly humus (partially decayed organic matter)

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A1-horizon

Back 80

humus has decayed further and mixed together w/ clay, silt, sand

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A2-horizon

Back 81

lighter-coloered
less organic matter

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nutrient-rich topsoil

Back 82

O and A1-horizons
dark in color, farmers till for planting crops

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B-horizon

Back 83

zone of accumulation - where ions precipitate to form new minerals and clay collects

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C-horizon

Back 84

material dervied from substrate (base) that's been chemically weathered and broken apart

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Factors to the diversity of soil

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1.) substrate composition and resistance
2.) climate
3.) slope steepness
4.) duration of soil formation
5.) vegetation type

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Climate's affect on soil

Back 86

more rain --> more leaching --> less fertile soil
temperate climate zone: good amt of rain
tropical/subtropical zone: too much rain, leaching
arid zone: not enough rain

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Laterite

Back 87

= Oxisol
tropical regions
minerals leached out
need treats to compensate for lost nutrients

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Pedocal

Back 88

= Aridisol
arid climate

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Pedalfer

Back 89

= alfisol
temperate climate