Geology 1010 FINAL EXAM

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What conditions favor fossil preservation?

- Low oxygen environment (prevents decay) - Rapid burial (prevent destruction by scavengers) - Presence of hard parts (bones, teeth, shells, preserve better than soft tissue)

Hydraulic Conductivity

A measure of how fluid flows in porous material

Vadose zone

A zone above the water table and below the land surface that is not saturated with water

What is a metamorphic aureole?

An area that surrounds rock that has been changed and undergone Metamorphosis

Where are conglomerates found?

Close to the sediment source

How many mass extinctions have there been?

Five

Chemical Sedimentary Rock

Minerals precipitated directly from water solutions

How much would sea level rise if all mountain glaciers melt? Greenland Ice Sheets? Antarctic ice sheets?

Mountain glaciers: 0.7 meters Greenland ice: 7 meters Arctic ice: 70 meters

What are surface features of sedimentary structures?

Mudcracks and ripple marks

Are earthquakes predictable?

No

Is the current rate of sea level rise unprecedented?

No, it is not unprecedented

Is the Earth a perfect sphere?

No. Spinning had caused the Earth to "bulge" around the Equator (This is due the fact that the Earth is comprised of many different chemicals)

What are the four kinds of seismic waves?

P-waves S-Waves Love Waves Rayleigh Waves

How does sorting affect primary porosity?

Poorly sorted = low porosity well sorted = high porosity

Equation to calculate porosity

Porosity = volume of voids/total volume

How does porosity vary with grain size, sorting, and packing?

Porosity goes up as grain size goes down

Porosity

Porosity is spaces in sediment

What are the 3 main minerals found in felsic magmas?

Potassium Feldspar, Quartz, Plagioclase

What is an extrusive igneous rock?

Rocks that are formed when lava hardens above the Earth's surface

What is an intrusive igneous rock?

Rocks that are formed when magma hardens beneath Earth's surface

Angular unconformity

Rocks underneath horizontally layered sediments are tilted or folded.

Aquifer

Rocks with high permeability containing groundwater

Rayleigh Waves

Rolls in wave motion, surface waves

What kind of rocks are fossils found in?

Sedimentary rocks

Types of Foliated Rock

Shale Slate, Phyllite, Schist, Gneiss Sharks Sometimes Play with Scientists and Grandmas

Compare groundwater flow through shale and sandstone

Shale: K= 10 to the -6- m/day, Q= 1 mL/day (¼ teaspoon/day) Sandstone: K= 1m/day, 1 m to the 3/day, (about 6 barrels)

How deep in Earth do earthquakes occur in divergent boundaries?

Shallow

How deep in Earth do earthquakes occur in convergent boundaries?

Shallow-Deep

How deep in Earth do earthquakes occur in collision zones?

Shallow-Intermediate

How does sorting vary with energy or transport distance?

Sorting will increase with more transport distance and lower energy

Volcanic Arcs

Subaerial eruptions at convergent margins, andesitic to rhyolitic magma

Where do subducted slabs go?

Subducted slabs sink, ultimately reaching the core-mantle boundary

What are the 3 types of differential stress we considered?

Tensional Compressional Shear

How many ice sheets are on Earth at present?

Three

Love Waves

Undulates laterally, surface waves

What is Colorado's state rock?

Yule marble

Strike-Slip Fault

birds eye view, forward and backward motion

What are the two kinds of crust?

oceanic and continental

What is the Moho?

the boundary between the crust and the mantle. Where seismic velocity increases abruptly.

How do magnetic anomalies (magnetic stripes) on the seafloor prove seafloor spreading?

• Stripes parallel to mid-ocean ridge. • Stripes are symmetric about the Ridge. • Stripes are due to orientation of magnetic minerals in sea floor rocks

What are the 4 processes involved in metamorphism?

-Heat -Pressure -Shear (pressure/force with direction) -Hydrothermal fluids

Stratovolcanoes

-High silica content -High viscosity -Andesitic-granitic composition -Explosive eruptions -Steep sided

Unconformity

-Long period of time of non-deposition -Gaps (we have no rock left in that time interval; maybe eroded?) in geologic record

What are the basic features of the seafloor spreading hypothesis?

1) Basalt magma rising at mid-ocean ridges makes new crust 2) Crust moves away from the ridge as new eruptions occur Accumulates sediment 3) Crust must sink into mantle somewhere--- this occurs at oceanic trenches

What conditions affect the deformation behavior of rock?

1) Temperature- warmer temps are more likely to have plastic behaviors 2) Pressure- higher pressure likely to have plastic behavior 3) Deformation rate- slower deformation favors plastic behavior 4) Composition of rock- softer rock types are more likely to have plastic behavior

Within a convergent boundary, where would these metamorphic environments be found, and what rocks would be produced?

1) low-temperature, high-pressure 2) high-temperature, low-pressure 3) high-temperature, high-pressure

What pressure/temperature conditions and metamorphic rock types are associated with the following:

1) regional metamorphism in a mountain belt 2) contact metamorphism around a magma chamber 3) subduction zone metamorphism

What does water table topography look like?

1. Vadose zone (unsaturated) 2. Water table boundary 3. Groundwater (saturated)

What is 1 mm in microns?

1000 microns

How long ago was the big bang?

13.7 Ga

How long did Big Bang nucleosynthesis go on, and which elements were made?

3 minutes Hydrogen and Helium

What causes sea level rise?

30% of sea level rise is from thermal expansion of the ocean 55% glaciers/ice sheets 25% other causes

Grain size of Silt

4-62 microns (gritty)

What is the circumference of the Earth?

40,000 km

What is the density of the Earth?

5.5 g/cm³

Grain size of Sand

62 microns - 2 mm (sandy)

What is the radius of the Earth?

6370 km

What fraction of geologic time is represented by the Precambrian Eon?

90%

What fraction of the Solar System mass is in the Sun?

99.9%

Grain size of Clay

< 4 microns (creamy)

Grain size of Pebbles

> 2 mm

What does Ga stand for?

A Billion Years

What does Ma stand for?

A Million Years

What is a glacier?

A body of ice that flows

What is a fault?

A break in the earth's crust

What is a nebula

A cloud of gas and dust containing the remnants of stars

What is a trench?

A deep canyon in the ocean floor

What is a rift valley?

A deep valley that forms where two plates move apart

Non-Foliated Rocks

A metamorphic rock that does not have parallel layers of mineral grains

What is the definition of rock?

A naturally occurring solid composed of minerals or glass or organic matter. Usually a mixture.

How does particle shape vary with energy or transport distance?

A particle becomes more round with more transport distance

Uniformitarianism

A principle that explain how geologic processes that occurred in the past can be explained by current geologic processes.

What is a mineral?

A pure substance Naturally-occurring Inorganic solid with a specific internal structure (crystal structure) A definable chemical composition

What is metamorphic grade?

A scale denoting the level of pressure and temperature involved in forming a particular metamorphic rock

What is the (current record) oldest rock on Earth?

Acasta Gneiss. 4.03 billion years old.

Glacial Accumulation

All forms of delivery of snow or ice to glacier (Snowfall, windblown, avalanche)

Where are the volcanoes found in a convergent boundary?

Along the volcanic arc

What is a silica tetrahedron?

An Anion containing 4 oxygen atoms and 1 silicon atom; can directly bond to others by sharing oxygen atoms.

What is a seamount?

An active volcano that occurs along the crest of the mid-ocean ridge. HOT SPOT!

What are magnetic declination?

Angle of offset between magnetic pole (where your compass needle points) and geographic pole

Where would the oldest rocks be found in a dome?

Anticline = Oldest rocks in the middle

What kind of fold is a dome?

Anticline with center point

What is apparent polar wander?

Apparent polar wander paths measured on different continents don't line up. Therefore, continents move!

What defines the beginning of the Phanerozoic Eon

Appearance of "visible life"

How does melt viscosity vary with composition? How does this affect the volcanic eruption style?

As you increase the silica content, magma becomes more viscous.

Felsic Eruption Style

Ash, lapilli, bombs, tephra, pyroclastic flow, lahars Caldera

What is partial melting?

At conditions between the solidus and the liquidus, the rock undergoes partial melting

What are the layers of the Earth, defined by chemical composition?

Atmosphere Crust Mantle Core

What are isotopes?

Atoms of the same element with different numbers of neutrons

What are the physical properties of oceanic crust?

Basalt Composition Fe + Mg Dense Really thin (5-7 km)

What are three extrusive igneous rocks?

Basalt: low Si, mafic (Mg + Fe) Andesite: intermediate Si Rhyolite: high Si, felsic

Where is Sandstone found?

Beach Shore

What is a hanging wall?

Block above the fault

Contact

Boundary between formations

Water table

Boundary between unsaturated and fully saturated zones Rule of thumb: water table is subdued version of the surface topography

What chemical is Limestone made of?

Calcium Carbonate

Biochemical Sedimentary Rock

Cemented shells of organisms

What are the time spans of the Phanerozoic period

Cenozoic 0-66Ma Mesozoic 66-252Ma Paleozoic 252-541Ma

Name the Eras in the Phanerozoic Eon

Cenozoic, Mesozoic, Paleozoic

Where is Earth's magnetic field generated?

Circulating liquid iron in the outer core generates the magnetic field

What was dated to determine the age of the Earth?

Claire Patterson used uranium-lead to determine the age of the Earth in a meteorite.

What defines glacier ice?

Coarse grains and contains air bubbles

How does composition of the Earth compare to composition of the Sun?

Composition of Earth is similar to the Sun, except for low H and He Volatiles lost in solar system formation

What does differentiated mean, with respect to a planet?

Comprised of layers that differ in chemical composition and in physical properties

Clastic Sedimentary Rocks

Conglomerate Breccia Sandstone Siltstone Shale Mudstone Can Bees Save Silver Sharks' Mouths

What evidence compelled Alfred Wegener to propose the continental drift theory in early 20th century?

Continental shift theory, archean rock assemblages match, ancient mountain ranges line opposite sides of the Atlantic, Fossils of extinct organisms found on different continents.

Why does the lithosphere thicken and the ocean deepen with distance away from a mid-ocean ridge axis?

Cooler and thicker lithosphere sinks into the asthenosphere

What is the Core's composition and density?

Core • Fe • Iron (Fe) alloy (mixture with a little nickel (Ni) and other elements) • Super dense: 10-13.5 g/cm3

What can we do to protect ourselves from earthquake hazards?

Create buildings with reinforced corners

What are internal features of sedimentary structures?

Cross-bedding indicates deposited in flowing water or air in dunes or ripples Also... fossils

What is the Crust's composition and density?

Crust • O + Si • Light silicate minerals • Density 2.6-3.2 g/cm3 • Thin: 8-75 km

What is fractional crystallization?

Crystallization of part of a magma, leaving behind melted rock with a different composition from the original magma

Where is Mudstone found?

Deep Marine

Where is Shale found?

Deep Marine

What does the moment depend upon?

Depends on energy released which depends on length and distance of rupture

How does the energy release of a Mw 7 compare with the energy release in a Mw 6 Earthquake?

Difference in 1 unit = 31 x more energy

How does the energy release of a Mw 7 compare with the energy release in a Mw 5 Earthquake?

Difference in 2 units = 1000 x more energy

How do we identify the location of an earthquake?

Difference in P Wave and S Wave arrival times at 3 different sources

Where is there a better potential for geothermal energy?

Differences in tectonic settings Plate boundary on the west, but the east coast is passive margin

What are the 3 deformation styles that occur in response to differential stress?

Displacement Change in orientation (rotation) Change in shape (distortion)

Index Fossils

Distinctive fossils used to establish and compare the relative ages of rock layers and the fossils they contain. These are useful because of their... - Widespread geographic distribution - Existence for a limited period of time (then went extinct) - Easily preserved in sedimentary rock

What is a strain?

Distortion or the response to stress

What kind of fold is a syncline?

Down Fold, limbs dip toward the hinge

In general, where do earthquakes occur within the Earth? Where do the deepest earthquakes occur? Why?

Earthquake belts are wide at convergent margins. Deepest earthquakes occur in the Wadati-Benioff zone (earthquake belt along the subducting slab)

What are tectonic plates, and what is a good way to identify their edges?

Earthquake epicenter maps do good job outlining plate boundaries.

What is the moment (M0) of an earthquake?

Energy released

How are metamorphic rocks from deep in the crust ever exposed on the surface?

Exhumation - from collision or erosion

Where is the High Plains Aquifer?

Extends across 7 states

Where is it fatter—around the equator or the poles?

Fatter around the equator Reference spheroid has radius 6378 km around equator and 6357 km around poles

What are the four categories of magma, and what wt% silica define them?

Felsic 66-76 wt% Intermediate 52-66 wt% Mafic 45-52 wt% Ultramafic 38-45 wt%

What causes changes in water table level?

Fluctuations in the water table level are caused by changes in precipitation between seasons and years.

What are 3 ways to melt rock?

Flux melting, decompression, application of heat

How much does lithostatic pressure increase with depth?

For every ~3km in depth, pressure increases by ~1 kbar

Lateral continuity

Formations are still continuous even in eroded area spans

What is an metamorphic rock?

Formed by recrystallization of other rocks under heat and pressure

What is an sedimentary rock?

Formed from fragments of other rocks

What is the principle of fossil succession?

Fossil organisms succeed one another in a definite and determinable order, and therefore any time period can be recognized by its fossil content.

How is magma composition affected by partial melting or fractional crystallization?

Fractional crystallization and partial melting changes magma from being mafic to felsic.

What component of the cryosphere is the most extensive?

Frozen ground

What are three intrusive igneous rocks?

Gabbro: low Si, mafic (Mg + Fe) Diorite: intermediate Si Granite: high Si, felsic

What is the eruption style of a volcano that is located on a hotspot?

Gentle, effusive eruption style

Glacial positive balance

Glacier advances, sea level falls

What control's a glacier's speed?

Glacier mass balance

Glacial negative balance

Glacier retreats, sea level rises

What are the two largest freshwater reservoirs on Earth?

Glaciers and polar ice

What are the components of the cryosphere?

Glaciers, permafrost, and sea ice

What variables determine hydraulic conductivity?

Grain size, grain shape and, fluid viscosity

What are the physical properties of continental crust?

Granitic Composition Less dense Thicker (35-40 km)

Why does subduction occur?

Gravity causes older, denser oceanic crust to sink beneath less dense continental crust

How common are great earthquakes (Mw > 8)? How frequent are lower magnitude Earthquakes?

Great ones aren't so common, lower magnitude EQs are EXTREMELY common

What are some hazards from earthquakes?

Ground shaking- building damage Landslides and rockfall Sediment Liquefaction: Fire Tsunamis

Normal fault (What is the definition and stress regime?)

Hanging wall moves down (below) relative to the footwall Stress regime: Extension (lengthened/expanded by movement of the fault)

Reverse fault

Hanging wall moves up (above) relative to footwall Stress regime: Compression (shortened/narrowed by movement of fault)

What are the 3 main causes (drivers) of metamorphism

Heat, Pressure, and Hydrothermal fluids

What does felsic mean?

High silica and light coloration

Volcanic domes or plugs

High viscosity, small, steep

Pore connectivity

Higher connectivity, higher permeability

We can assess hazard from

History of earthquakes Monitoring of earthquakes Monitoring plate motion Understanding plate tectonics context and subsurface structure

Types of Non-Foliated Rock

Hornfels (silicates) Quartzite (quartz) Marble (calcium carbonate)

Where are hot spots relative to tectonic plates?

Hot spots are fixed relative to plates moving around on the surface

Hydrothermal Fluids

Hot water with dissolved ions and volatiles

What differs between the inner planets and the outer planets of the Solar System?

Hotter (inner) region where "refractory" materials dominate (solidify at high temperatures), while the Frost Line separates Colder (outer) region where volatiles (gases and ices) dominate

What were the objections to Wegener's continental drift theory?

How do continents move? Why do continents move? Coastal erosion by waves should erode coastline shapes

How is radioactivity used as a clock to date rocks?

If we know the half-lives of both the parent and the daughter atoms, we can determine the age of a rock by looking at the ratio of parent to daughter atoms. This picture should help.

Oxidation/hydration cracking

In biotite tetrahedral sheets Iron oxidises and biotite expands

What is the ratio of accumulation area to total glacier area for a stable glacier?

In stable glacier, accumulation at least 60% of glacier area

What is the moment magnitude (Mw) of an earthquake?

Index is called Moment Magnitude Mw Reported on logarithmic scale

What is an example of an active collision zone on Earth now?

Indian subplate combining with Eurasian plate

Formation

Interval of sedimentary strata composed of a specific rock type or group of rock types that can be traced over a wide area

What are the 3 main minerals found in mafic magmas?

Iodine, Pyroxene, Plagioclase

Oxidation

Iron reacts with water to make iron oxides

What are the three most abundant elements in Earth (by mass)?

Iron, Silicon, Oxygen

Confined Aquifer

Isolated from the Earth's surface. An aquifer surrounded by a layer of impermeable rock or clay that impedes water flow

Why is the High Plains Aquifer important to the U.S.?

It makes up 30% of groundwater irrigation

Who wrote "we find no vestige of a beginning, no prospect of an end", and what were they talking about?

James Hutton; geologic time and the principle of uniformitarianism

What is a supercontinent?

Jigsaw puzzle-like fit of continents together

What causes sediments to mobilize?

Landslides, rock fall, debris flows and creep

What is a shield?

Large area of exposed Precambrian crystalline igneous High-grade metamorphic rocks that form tectonically stable areas.

Breccia

Large clasts compiled together (Angular)

Conglomerate

Large grains compiled together (Rounded)

Pore Size

Large pores, higher permeability

What kind of lava is associated with volcanoes located on hotspots?

Lava is basaltic, mafic, low silica content, low viscosity

What is foliation?

Layers (visible in gneiss or schist) or alignment in rock form by a preferred orientation (in metamorphic rocks) Alignment of platy minerals (alternating light and dark minerals)

Exfoliation jointing

Like an onion skin, joints are fracture planes. Unloading is erosion taking load off rock. Created by erosion unloading; only found in strong, otherwise flawless rock.

Biochemical Sedimentary Rocks

Limestone and chert

Pattern of sedimentary bedding that shows transgression?

Limestone, Shale, Sandstone

How does the mobility (viscosity) of lava vary with silica content?

Low silica = low viscosity (runny and thin) High silica = high viscosity (thick)

What does mafic mean?

Low silica and dark/colored coloration

Shield volcanoes

Low silica content, low viscosity, gentle slopes

What is the "cone of depression"?

Lowered water table around a well

Organic Sedimentary Rock

Made of carbon-rich relics of plants or other organics

Clastic Sedimentary Rock

Made of particles from other rocks

How does magma differ from lava?

Magma is molten rock beneath Earth's surface; lava is molten rock at Earth's surface.

What is magnetic inclination?

Magnetic reversals recorded in the rocks. The field lines dip

What is the Mantle's composition and density?

Mantle • O + Si + Mg • 2/3 of the mass of Earth • Dense silicate minerals • Density: 3.3 to 5.4 g/cm3 • Extends to 2900 km depth

Where are transform boundaries found?

Many transform boundaries are found on the seafloor, where they connect segments of diverging mid-ocean ridges.

Nonconformity

Metamorphic or igneous rocks in contact with sedimentary strata

Metamorphic Rock

Metamorphic rock is rock formed from pre-existing rock (the protolith), by solid state change (no melting), in response to changes in its environment.

Where are metamorphic rocks generally found?

Metamorphic rocks are formed mainly in the lithosphere, wherever there is high pressure and high temperature. ... Metamorphic rocks are most abundant at convergent plate boundaries, but can occur in other areas where there are increased pressures and/or temperatures

What is a Mid-Ocean Ridge?

Mid-ocean ridges form long chains of mountains that rise up from the ocean floor.

Dissolutions

Minerals dissolve in water producing salt solutions and often clay minerals.

What are the main steps of formation of our Solar System?

Nebula Protoplanetary Disk Rings of Planetesimals The Eight Planets

What are the consequences of negative or positive mass balance?

Negative mass balance over many years leads to glacier retreat, while a positive balance over many years will advance.

Where would the oldest rocks be found relative to the fold axis in a Syncline?

Oldest on the limbs, youngest on the axis

Where would the oldest rocks be found relative to the fold axis in an anticline?

Oldest rocks on the axis, youngest on the limbs

In short, why do earthquakes occur repeatedly on the same failure surface?

Once a failure has occurred, that location is a plane weakness, makes it more likely for another failure to occur there, easiest place for a slip to be accommodated

What does "protolith" mean?

Original rock before change in property occurred

Products of Chemical Weathering

Oxide minerals & Clay minerals

What does it mean when rocks are red?

Oxidizing, most likely on land

What are the three most abundant elements in Earth's crust (by mass)?

Oxygen, Silicon, Aluminum

Which is the faster of the two body waves?

P waves are faster than S waves

Basalt Eruption Style

Pahoehoe, a'a, pillow lava

What is the Wadati-Benioff zone?

Pattern of shallow-deep EQs map the subducting slab

What is permafrost?

Perennially (2 or more years) frozen ( below 0 degrees celsius) ground

What is Peridotite, and where is it the dominant mineral?

Peridotite is a super ultramafic mineral that is predominantly located in the mantle

Disconformity

Periods of non-deposition and erosion, without tilting or folding of the rocks, produce a disconformity. Sedimentary layers above and below the disconformity are parallel.

Permeability

Permeability describes the ease of fluid movement or flow in a rock

Why are planets spherical, rather than potato or snowman shaped?

Planets must have enough mass and be made up of a material that is able to deform under the influence of gravity.

How does glacier ice form?

Plastic deformation

What is the asthenosphere and what are its physical properties?

Plastic layer Warmer (temperature >1280°C)

Differentiate plastic deformation and brittle deformation

Plastic: Recoverable deformation Brittle: Unrecoverable deformation

How do plates differ from continents?

Plates are bigger than continents

What are divergent plates?

Plates move apart Hot mantle (asthenosphere) rises, melts to form magma Magma rises Forms new crust with characteristic layering Bottom: Gabbro Middle: Basalt dikes Top: Pillow basalt Cooler and thicker lithosphere sinks into the asthenosphere

What are convergent plates?

Plates move toward each other Old oceanic plates are denser than the asthenosphere Plate bends, and sinks down into the mantle Earthquakes (breaking rock on faults) occur along the subducting slab (plate)

What are transform plates?

Plates slide past each other Earthquakes are generated No volcanic activity

What is the hypocenter (or focus) of an earthquake?

Point underground where earthquake occurred

What are the names of the 5 mass extinctions?

Present Cenozoic - Age of mammals 65.5 MYA - mass extinction (meteorite impact) Mesozoic - Age of dinosaurs (Reptiles) 251 MYA - mass extinction (volcanism) Paleozoic - Age of Marine Organisms 542 MYA - Cambrian explosion (dramatic increase in abundance, complexity, diversity of life)' Precambrian Late - age of soft-bodied life Early - age of single-celled life

Lithification

Process of sediments compacting under pressure.

What is groundwater recharge?

Process of water going through the soil and back to the aquifer

Glacial Ablation

Processes that remove ice (Melting, evaporation, removal by wind, calving/splitting of icebergs)

Darcy's Law

Q = -K * i * A K is hydraulic conductivity I is delta h/L (head difference and length, basically slope) A is cross section area of tube

Unconfined Aquifer

Reaches the Earth's surface. An aquifer made of porous rock covered by soil out of which water can easily flow

Thrust Fault (What is the definition and stress regime?)

Reverse fault w low angle (less than 30º) Stress regime: Compressive (shortening/narrowed by movement of fault)

What is the lithosphere and what are its physical properties?

Rigid layer 100-150 km thick Cooler (temperature <1280°C)

Foliated Rocks

Rock that contains parallel layers of flat and elongated minerals

Inclusions

Rock that formed before is engulfed in the intruding rock

What is an igneous rock?

Rocks formed from magma (molten rock)

Sedimentary Rock

Rocks made of fragments of other rocks cemented together. Minerals precipitated from water solutions at Earth's surface.

What is the typical organization of sedimentary units from shoreline beaches to deep ocean?

Sandstone Siltstone Shale Mudstone

Pattern of sedimentary bedding that shows regression?

Sandstone, Shale, Limestone

How are sedimentary rocks formed?

Sediment undergoes lithification

Original horizontality

Sedimentary rocks (and sedimentary rocks only) are formed in roughly horizontal layers

What is the Frost Line?

Separates Colder (outer) region where volatiles (gases and ices) dominate.

How deep in Earth do earthquakes occur in transform boundaries?

Shallow

Where is Limestone found?

Shallow Marine

Where is Siltstone found?

Shallow Marine

What is the geoid?

Shape the earth's surface would have if only gravity and rotation were involved, and other forces were absent

What kind of volcanoes are located on hotspots?

Shield volcanoes: low slopes and lava flows

What are the limbs of a fold?

Sides or flanks of folds

What chemical composition does chert have?

Silica

What is Granite?

Silica Content: Felsic/High Texture: Course Freezing Temp: Low (900-600C) Density: 2.5 g/cm³

What is Rhyolite?

Silica Content: Felsic/High Texture: Fine Freezing Temp: Low (900-600C) Density: 2.5 g/cm³

What is Diorite?

Silica Content: Intermediate Texture: Coarse Freezing Temp: Medium/Low (1000-900C) Density: 2.8 g/cm³

What is Andesite?

Silica Content: Intermediate Texture: Fine Freezing Temp: Medium/Low (1000-900C) Density: 2.8 g/cm³

What is Gabbro?

Silica Content: Low/Mafic Texture: Coarse Freezing Temp: High (1100-1200) Density: 3.0 g/cm³

What is Basalt?

Silica Content: Mafic/Low Texture: Fine Freezing Temp: High (1100-1200C) Density: 3.0 g/cm³

What are Feldspars?

Silicate Mineral Family Silica Content: High Mg-Fe Content: Low-Felsic Color: Light Density: 2.6 g/cm³ Melting Point: High -> 1000-1200C

What are Pyroxenes?

Silicate Mineral Family Silica Content: Low Mg-Fe Content: High-Mafic Color: Dark Density: 3.2 g/cm³ Melting Point: High -> 1000-1200C

What are Amphiboles?

Silicate Mineral Family Silica Content: Low-Medium Mg-Fe Content: High-Mafic Color: Dark Density: 3.2 g/cm³ Melting Point: High -> 1000-1200C

What are Olivines?

Silicate Mineral Family Silica Content: Lowest Mg-Fe Content: Very High-Ultra mafic Color: Green Density: 3.3 g/cm³ Melting Point: High -> 1000-1200C

What are Micas?

Silicate Mineral Family Silica Content: Medium Mg-Fe Content: High-Mafic Color: Dark or Light Density: 2.8 g/cm³ Melting Point: High -> 1000-1200C

What is Quartz?

Silicate Mineral Family Silica Content: Very High Mg-Fe Content: No Cations Color: Light Density: 2.65 g/cm³ Melting Point: Lower -> 650-900 C

What are the most abundant class of minerals in the Earth's crust and mantle?

Silicate minerals make up 95% of the crust and mantle, and of these, feldspars and quartz make up 75% of the crust

What kind of fold is a monocline?

Simple bend makes it not horizontal Only one limb Product of a reverse fault that occurred deep in the crust

How does grain size vary with energy or transport distance?

Size decreases with more transport distance and lower energy

How does ice flow?

Sliding

What do we mean by geologic structure?

Small scale deformation of earth's crust

Thermal expansion cracking

Spikes in surface temperature cause rock to expand (caused by fire, solar radiation, air temp)

What is the epicenter of an earthquake?

Spot above hypocenter above ground

How fast do plates move, and how do we know?

Spreading centers: 3-15 cm/yr Absolute rates measured directly from GPS receivers

What type of volcanoes are located on a convergent margin/subduction zone?

Stratovolcanoes

What is stress, and how does it differ from force?

Stress = Force acting over an area

What happens in collision zones?

Subduction zone is closed up Subducted slab (oceanic lithosphere) detaches Slab sinks into mantle Continental crust collides, thickens, fractures, forming Collisional mountain belt

Mid ocean ridges (In terms of volcanoes)

Submarine eruptions, basaltic lava types. In middle of rift---> not much volcanic edifice

Where would the oldest rocks be found in a bowl?

Syncline = Oldest rocks on the outside

What kind of fold is a bowl?

Syncline with center point

How is it possible to accumulate thousands of meters of sediments in an area?

Tectonic shifts that cause rifts, basins, and any other thinning of the crust tend to shift some of the mantle out of the way, creating space for sedimentation

What does dip measure?

The acute angle that a rock surface makes with a horizontal plane.

Relative Age

The age of a rock compared to the ages of rock layers

Absolute Age

The age of a rock given as the number of years since the rock formed.

How does the age of the ocean change with distance away from the mid-ocean ridge axis?

The age of the ocean increases the further it gets away from the MOR

Saturated zone

The area of permeable rock or soil in which the cracks and pores are totally filled with water.

Why doesn't the low spot fill with sediment?

The asthenosphere that is below the sediment, deforms from the weight of the sediments above.

How does the density of the Earth compare to the density of a typical rock?

The average density of a rock is ~2.7 g/cm³ while the density of the Earth as a whole is 5.5 g/cm³

What is a footwall?

The block of rock that forms the lower half of a fault

How do we know about the Cretaceous Interior Seaway?

The bottom of the seaway had very little oxygen, which meant that any of the unique sea creatures that died were fossilized

How does the depth of the ocean change with distance away from the mid-ocean ridge axis?

The depth of the ocean increases the further it gets away from the MOR

What does strike measure?

The direction of the line formed by the intersection of a rock surface with a horizontal plane

What is the axis of a fold?

The intersection of the axial plane with one of the strata of which the fold is composed

Why is the magnetic field important for life on Earth?

The magnetic field protects the Earth and the living creatures on the planet from solar wind.

What is radioactive decay?

The process in which unstable isotopes decay into other elements and emit radiation as they attempt to become more stable

Stellar Nucleosynthesis

The production of new, larger atoms by fusion reactions in stars created atoms Li -> Fe

Supernova Nucleosynthesis

The production of new, larger atoms by supernovae. Created atoms larger than Fe

What are fossils?

The remains or traces of organisms preserved in rocks

What is non-permanent deformation of rocks/surfaces?

The rock can return to its original shape when the stress is removed

What is permanent brittle deformation?

The rock cannot return to its original shape when the stress is removed

What is elastic deformation?

The rock returns to its original shape when the stress is removed

What kinds of igneous rocks are associated with convergent boundaries?

The rocks are mostly mafic

What kinds of igneous rocks are associated with divergent boundaries?

The rocks are mostly mafic

What do we mean by "geologic history"

The sequence of events recorded in rocks and cross-cutting relationships

Primary porosity

The space that remains between solid grains or crystals immediately after sediment accumulates or rock forms.

What is paleomagnetism?

The study of the magnetic properties of rocks. Features of the magnetic field are preserved in volcanic rocks (and some sedimentary rocks)

How does thickness of lithosphere change with distance away from the mid-ocean ridge axis?

The thickness of lithosphere increases the further it gets away from the MOR

How does thickness of sediment change with distance away from the mid-ocean ridge axis?

The thickness of sediment thins the further it gets away from the MOR

What is the half-life?

The time it takes for half of a group of a radioactive element's isotopes to decay

What is drainable water in storage?

The total amount of water that can be withdrawn in an aquifer.

What is an earthquake?

The vibration of Earth produced by the rapid release of energy

What is specific yield (with respect to groundwater)?

The volume of water released per volume of aquifer

What feeds springs and most flow in rivers (especially that between storms and snowmelt)?

The water flow from recharge areas to discharge areas, or where the water table intersects the ground surface

What are the two largest uses of water in the US?

Thermal electric power and irrigation

What does it mean when rocks are black/blue?

They are organic rich with little to no oxygen

Glacial total net balance

Total net balance = accumulation - ablation

Biological processes

Tree roots, fungal hyphae growing towards and through minerals.

What is the current rate of sea level rise?

Trend is 3.1 mm/year in sea level rise

What kind of fold is an anticline?

Up Fold, limbs dip away from the hinge

Tectonic Jointing

Uplift and displacement of the crust breaks rock, forming faults and pervasive sets of fractures called joints.

How are major time period boundaries defined?

Using fossils and the principle of superposition

What composition do volcanoes on a convergent margin/subduction zone have?

Volcanic arc has intermediate silica content, viscous magma where bubbles cannot escape easily

Why are volcanoes and trenches both associated with convergent boundaries?

Volcanic arcs parallel the trench, sit on the over-riding plate

What is the difference between a continental volcanic arc and an island arc?

Volcanic island arc forms on the overriding plate, while Continental volcanic arc forms on the continental overriding plate

Frost-cracking

Water in cracks might not freeze at exactly 0º C Water can migrate through porous material to freezing area.

What is a marine regression?

Water levels fall away from the shore

What is a marine transgression?

Water levels rise towards the shore

What are parent and daughter atoms?

We can measure the ratio of parent and daughter atoms to determine the geologic age. Parent atoms are the original isotopes, whereas daughter atoms are the newer isotopes.

Sediment Liquefaction

When pressure in the water in the pores push sediment grains apart so that they become surrounded by water and no longer rest against each other, and the sediment becomes able to flow like a liquid

What is the hinge line of a fold?

Where the limbs of the fold meet

How did post-WWII research lead to development of the theory of seafloor spreading?

World War II development of sonar led to mapping and revealed seafloor topography

Cross-cutting relationships

Younger features cut across older ones

Superposition

Youngest sedimentary rocks on top

What is a volcanic arc?

a row of volcanoes that forms on the overriding plate near a subduction zone

What does crystal structure mean?

atoms are arranged in a repeated, orderly pattern

S-Waves

back and forth, body waves, secondary waves, slower than p-waves

Types of sedimentary rocks

clastic, chemical, organic and biochemical

Oblique slip fault

combination of strike-slip and dip-slip

What are the three types of plate boundaries?

divergent, convergent, transform

What is the eruption style of a volcano that is located on a convergent margin/subduction zone?

explosive eruption: tephra (ash+lapilli+bombs)

What is an accretionary prism?

faulted sediments scraped up by subduction

What does geothermal gradient mean, and what is a typical geothermal gradient?

geothermal gradient = change in temperature with depth dt/dz (t is temp in C, z is depth in km) Usually about 25 C/km, but it varies from place to place Typically, west US has higher geothermal gradients

What is an abyssal plain?

large flat areas on the ocean floor

Intraplate Volcanism

mantle plume (hotspot), volcanic ocean islands

Left Lateral Fault

straddle fault→ Left foot comes towards you

Right Lateral Fault

straddle fault→ Right foot comes towards you

P-Waves

up and down, body waves, primary wave, travels through all layers of earth

What are the categories of organization of silica tetrahedra that define the 6 silicate mineral families?

• Silica content • Organization of silica tetrahedra • Types of cations present • Density


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