Geology 105- Final Exam Study Guide

What is the key difference between weathering and erosion?

Weathering breaks down rocks, while erosion transports them.

How are sedimentary rocks formed in the rock cycle?

Sedimentary rocks form from the accumulation and lithification of sediments derived from other rocks.

How are sedimentary rocks related to igneous and metamorphic rocks?

Sedimentary rocks can be formed from the weathering and erosion of igneous and metamorphic rocks.

Contrast clastic, biochemical, and chemical sediments.

Clastic sediments are fragments of other rocks, biochemical sediments are remains of organisms, and chemical sediments precipitate from solution.

Provide examples of clastic sedimentary rocks and how they form.

Shale (formed from compacted mud), sandstone (formed from cemented sand grains), conglomerate (formed from cemented gravel).

Provide examples of biochemical sedimentary rocks and how they form.

Limestone (formed from shells and skeletons of marine organisms), coal (formed from compacted plant matter).

Provide examples of chemical sedimentary rocks and how they form.

Rock salt (formed from evaporated seawater), gypsum (formed from evaporated seawater).

What is lithification?

The process by which sediments are compacted and cemented to form sedimentary rocks.

Explain compaction in the context of sedimentary rock formation.

The process by which the weight of overlying sediments reduces pore space and volume in the sediment.

Explain cementation in the context of sedimentary rock formation.

The process by which dissolved minerals precipitate in the pore spaces of sediments, binding them together.

What are sedimentary structures?

Features formed during or shortly after deposition of sediment, such as bedding, ripple marks, and mud cracks.

Give examples of sedimentary structures.

Bedding, cross-bedding, ripple marks, mud cracks, graded bedding

How can mud cracks be interpreted in terms of their formation environment?

Mud cracks indicate alternating wet and dry conditions.

How can ripple marks be interpreted in terms of their formation environment?

Ripple marks indicate flowing water or wind.

What is a depositional environment?

A specific physical, chemical, and biological setting where sediments accumulate.

How can sedimentary structures help identify the depositional environment?

Specific sedimentary structures are characteristic of certain depositional environments (e.g., ripple marks in a riverbed).

What is abrasion?

The process of wearing down or rubbing away by means of friction.

How can grain size be used to determine the transport mechanism of a sedimentary rock?

Larger grain sizes indicate higher energy transport mechanisms (e.g., fast-flowing rivers).

How can grain shape be used to determine the transport mechanism of a sedimentary rock?

More rounded grains suggest longer transport distances.

How can grain sorting be used to determine the depositional environment of a sedimentary rock?

Well-sorted sediments indicate consistent energy conditions (e.g., a beach).

What are sedimentary facies?

A body of sediment with distinctive characteristics reflecting a particular depositional environment.

What are the typical sedimentary facies of a meandering stream?

Channel deposits (gravel, sand), point bar deposits (sand, silt), floodplain deposits (mud, clay).

What is an ocean transgression?

The advance of the sea over land.

What is an ocean regression?

The retreat of the sea from land.

Explain how sedimentary facies help interpret rising and falling sea levels.

Changes in sedimentary facies vertically indicate changes in sea level over time (e.g., a transition from marine shale to beach sandstone indicates regression).

Explain the formation of metamorphic rocks in the rock cycle.

Metamorphic rocks form from pre-existing rocks that are changed by heat, pressure, or chemically active fluids.

How are metamorphic rocks related to the other two rock types?

Metamorphic rocks are formed from igneous or sedimentary rocks through metamorphism.

How do metamorphic rock formation processes differ from igneous and sedimentary?

Metamorphic rocks form from changes to existing rocks without melting (unlike igneous) or surface processes (unlike sedimentary).

What are the two main classes of metamorphic rocks?

Foliated and non-foliated.

What is recrystallization?

The process by which minerals change size and shape without changing composition during metamorphism.

What is metasomatism?

The change in a rock's composition by fluid transport of chemical substances.

What is foliation in metamorphic rocks?

A parallel alignment of platy minerals (like mica) or compositional banding in a metamorphic rock.

How are recrystallization and foliation related?

Recrystallization can facilitate alignment of minerals, leading to foliation.

What is lithostatic pressure?

Pressure exerted equally on a rock from all directions due to the weight of overlying rocks.

What is directed pressure?

Pressure exerted unequally on a rock in one or more directions.

Which type of pressure leads to foliation?

Directed pressure.

Will a rock composed only of quartz or calcite become foliated under directed pressure?

No, because these minerals are equant (equal dimensions in all directions) and do not easily align.

How does foliation occur in rocks with biotite or elongated minerals under directed pressure?

Elongated or platy minerals align perpendicular to the direction of maximum stress.

Will a rock with biotite become foliated under lithostatic pressure?

No, because lithostatic pressure is equal in all directions and does not cause mineral alignment.

What is an index mineral?

A mineral that forms within a specific range of temperature and pressure conditions during metamorphism.

What is a geobarometer?

A mineral or mineral assemblage that indicates the pressure at which a metamorphic rock formed.

What is a geothermometer?

A mineral or mineral assemblage that indicates the temperature at which a metamorphic rock formed.

What are metamorphic facies?

A set of metamorphic mineral assemblages that indicate a specific range of pressure and temperature conditions.

What are the general pressure and temperature conditions of the zeolite facies?

Low temperature, low pressure.

What are the general pressure and temperature conditions of the hornfels facies?

High temperature, low pressure.

What are the general pressure and temperature conditions of the blueschist facies?

Low temperature, high pressure.

What are the general pressure and temperature conditions of the greenschist facies?

Intermediate temperature and pressure.

What are the general pressure and temperature conditions of the amphibolite facies?

High temperature, intermediate to high pressure.

What are the general pressure and temperature conditions of the granulite facies?

Very high temperature and pressure.

What are the general pressure and temperature conditions of the eclogite facies?

Very high pressure and high temperature.

What is an earthquake?

A sudden release of energy in the Earth's crust that creates seismic waves.

Along what geologic features do most earthquakes occur?

Faults, especially at plate boundaries.

What is stress?

Force applied per unit area.

What is strain?

Deformation resulting from stress.

What is the elastic rebound theory?

The theory that earthquakes occur when built-up stress is suddenly released along a fault.

What is the earthquake cycle?

The process of stress buildup, rupture (earthquake), and aftershocks repeating over time.

What is a fault?

A fracture in the Earth's crust along which movement has occurred.

What is an earthquake focus?

The point within the Earth where an earthquake originates.

What is an earthquake epicenter?

The point on the Earth's surface directly above the focus of an earthquake.

What is a seismic wave?

An elastic wave generated by an earthquake or explosion.

What are seismic body waves?

Seismic waves that travel through the Earth's interior.

What are seismic surface waves?

Seismic waves that travel along the Earth's surface.

What is a P-wave?

A compressional seismic body wave that can travel through solids, liquids, and gases.

What is an S-wave?

A shear seismic body wave that can only travel through solids.

Which type of seismic wave is fastest?

P-wave.

Which type of body wave cannot pass through liquids?

S-wave.

What is a Rayleigh wave?

A type of seismic surface wave that causes vertical ground motion.

What is a Love wave?

A type of seismic surface wave that causes horizontal ground motion.

What is a seismograph station?

A location equipped with a seismograph to detect and record seismic waves.

What is a seismogram?

A record of seismic waves produced by a seismograph.

What is the Mercalli Intensity Index?

A qualitative scale that measures the intensity of an earthquake based on its effects on people and structures.

What is the Richter Magnitude scale?

A quantitative scale that measures the magnitude of an earthquake based on the amplitude of seismic waves.

How does the type of geologic substrate affect earthquake damage?

Soft sediments amplify ground shaking more than hard bedrock.

What is liquefaction?

The process where saturated soil loses strength and stiffness due to shaking during an earthquake and behaves like a liquid.

What is resonance?

The tendency of a system to oscillate with greater amplitude at a specific frequency.

What is a tsunami?

A series of ocean waves caused by a large displacement of water, typically from an earthquake.

What is a seismic gap?

A segment of an active fault that has not experienced a significant earthquake for a long period.

What are common types of hazards associated with earthquakes?

Ground shaking, landslides, liquefaction, tsunamis, and fires.

Why do rocks deform?

Rocks deform due to applied stress.

What are brittle and ductile deformation?

Brittle deformation involves fracturing, while ductile deformation involves flowing.

What are tensional, compressional, and shearing stresses?

Tensional stress is pulling apart, compressional stress is squeezing together, and shearing stress is sliding past each other.

What is the difference between stress and strain?

Stress is the force applied to a rock, and strain is the rock's deformation in response to the stress.

What are strike-slip faults?

Faults where the movement is horizontal and parallel to the strike of the fault.