Midterm 2

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What is a hanging wall?

Block above the fault

What chemical is Limestone made of?

Calcium Carbonate

Where are conglomerates found?

Close to the sediment source

What is a strain?

Distortion or the response to stress

What kind of fold is a syncline?

Down Fold, limbs dip toward the hinge

Chemical Sedimentary Rock

Minerals precipitated directly from water solutions

What are surface features of sedimentary structures?

Mudcracks and ripple marks

Are earthquakes predictable?

No

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)

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)

Foliated Rocks

Rock that contains parallel layers of flat and elongated minerals

Rayleigh Waves

Rolls in wave motion, surface waves

Types of Foliated Rock

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

How deep in Earth do earthquakes occur in divergent boundaries?

Shallow

How deep in Earth do earthquakes occur in transform 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

What is the geoid?

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

What are the limbs of a fold?

Sides or flanks of folds

What kind of fold is a bowl?

Syncline with center point

What are the 3 types of differential stress we considered?

Tensional Compressional Shear

What is a footwall?

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

Love Waves

Undulates laterally, surface waves

Frost-cracking

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

Strike-Slip Fault

birds eye view, forward and backward motion

What are the 4 processes involved in metamorphism?

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

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 is 1 mm in microns?

1000 microns

Grain size of Silt

4-62 microns (gritty)

Grain size of Sand

62 microns - 2 mm (sandy)

Grain size of Clay

< 4 microns (creamy)

Grain size of Pebbles

> 2 mm

What is a fault?

A break in the earth's crust

Non-Foliated Rocks

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

How does particle shape vary with energy or transport distance?

A particle becomes more round with more transport distance

What is metamorphic grade?

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

What is a metamorphic aureole?

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

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

Where is Sandstone found?

Beach Shore

Biochemical Sedimentary Rock

Cemented shells of organisms

Clastic Sedimentary Rocks

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

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

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)

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 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

How much does lithostatic pressure increase with depth?

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

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

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)

Hydrothermal Fluids

Hot water with dissolved ions and volatiles

Oxidation/hydration cracking

In biotite tetrahedral sheets Iron oxidises and biotite expands

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

Index is called Moment Magnitude Mw Reported on logarithmic scale

Oxidation

Iron reacts with water to make iron oxides

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)

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

Organic Sedimentary Rock

Made of carbon-rich relicts of plants or other organics

Clastic Sedimentary Rock

Made of particles from other rocks

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

Dissolutions

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

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

Chemical Weathering Products

Oxide minerals & Clay minerals

What does it mean when rocks are red?

Oxidizing, most likely on land

Which is the faster of the two body waves?

P waves are faster than S waves

What are the four kinds of seismic waves?

P-waves S-Waves Love Waves Rayleigh Waves

Differentiate plastic deformation and brittle deformation

Plastic: Recoverable deformation Brittle: Unrecoverable deformation

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

Point underground where earthquake occurred

Lithification

Process of sediments compacting under pressure.

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

Where is Limestone found?

Shallow Marine

Where is Siltstone found?

Shallow Marine

What chemical composition does chert have?

Silica

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

What do we mean by geologic structure?

Small scale deformation of earth's crust

How does sorting vary with energy or transport distance?

Sorting will increase with more transport distance and lower energy

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

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

Stress = Force acting over an area

Where would the oldest rocks be found in a bowl?

Syncline = Oldest rocks on the outside

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.

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 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

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

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 is an earthquake?

The vibration of Earth produced by the rapid release of energy

What does it mean when rocks are black/blue?

They are organic rich with little to no oxygen

Biological processes

Tree roots, fungal hyphae growing towards and through minerals.

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.

What is a marine regression?

Water levels fall away from the shore

What is a marine transgression?

Water levels rise towards the shore

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

What is Colorado's state rock?

Yule marble

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 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

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


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