Geology 6

What is an accretionary wedge, and how does it form?

An accretionary wedge is an accumulation of deformed, thrust-faulted sediments and scraps of ocean crust. This wedge is plastered against the edge of the overriding plate from the subducting plate.

How is brittle deformation different from ductile deformation?

Brittle deformation describes a rock breaking as a result of stress, whereas ductile deformation describes a rock bending or folding as a result of stress.

Where are tectonic plates located?

Earth's surface

What is meant by elastic rebound?

Elastic rebound refers to how the slippage along a fault (i.e., earthquake) allows the deformed rock to regain its original shape in a new location.

With regard to earthquakes, what distinguishes intensity from magnitude?

Magnitude is a measure of how much energy is released by the earthquake, but intensity is a rough measure of local shaking

The Appalachian Mountains were formed when ________ and ________ collided more than 250 million years ago.

North America; Africa

Refer to the drawing below to review the different types of folds.

One side of the anticline dips more steeply than the other. At least one of the folds in this outcrop is asymmetrical.

motion that involves compression and expansion of the material through which it passes; may pass through solids, liquids, and gases

P wave

Which kind of seismic wave is fastest-moving?

P waves

What are the differences between P waves, S waves, and surface waves?.

P waves are the fastest and have the lowest amplitudes; S waves are the second fastest and have the second lowest amplitudes; surface waves are the slowest and have the highest amplitudes.

Which of the following best describes why the 2010 earthquake in Chile caused a large tsunami while the 2010 earthquake in Haiti only caused a small and local tsunami?

The earthquake in Haiti was the result of motion on a transform boundary, which does not produce any vertical motion of the sea floor, whereas the Chilean earthquake was the result of motion along a convergent plate boundary, which does.

How are faults, hypocenters, and epicenters related?

The hypocenter is the exact point underground along a fault where the slippage of the two blocks of rock occurs. The epicenter is the point on Earth's surface that is directly above the hypocenter.

Which layer is indicated by the letter B in the diagram and what is its composition?

The mantle. It is made of peridotite.

Which of the following statements about terranes is most accurate?

The margins of many continents have grown through the accretion of terranes.

Which one of the following is true of most tsunamis?

They are usually started by sudden movement on a megathrust fault, and have wavelengths that are many kilometers long and wave heights of less than a meter.

What is a tsunami?

a large ocean wave generated when a megathrust fault suddenly lifts a slab of seafloor

What is a terrane?

a slice of lithosphere that has been added to the margin of a continent during plate collision

What is necessary to create typical Andean-type mountain belts?

a subduction zone

Sediment scraped off the subducting plate builds up in a(n) ________.

accretionary wedge

Which of the following results from ductile deformation? Choose all that apply

an anticline a syncline a basin A dome

What kind of fold is illustrated in this photograph? At what sort of tectonic boundary situation is it likely to have formed?

anticline; convergent

The distance between a seismological recording station and the earthquake source is determined from the ________.

arrival times of P and S waves

Which of the following terms means "weak sphere"?

asthenosphere

Oceanic crust is primarily composed of ________.

basalt and gabbro

In addition to the destruction created directly by seismic vibrations, how else can earthquakes cause destruction? PLEASE SELECT ALL THAT APPLY.

by triggering a landslide by triggering a tsunami by triggering a firestorm within populated areas

How did the Himalayas form?

collision of India and Eurasia

Which type of force is responsible for reverse fault formation?

compressional force

Most orogenesis occurs along ________ plate boundaries.

convergent

In the plate tectonics model, which type(s) of plate boundary(ies) is/are most directly associated with Earth's major mountain belts?

convergent boundary

What type of deformation is shown in the Gigapan image?

ductile

When an earthquake occurs, energy radiates in all directions from its source region, called the ________, the spot in Earth's crust where a fault slips.

epicenter

What is a fault?

fractures along which rocks move

What does the Modified Mercalli Intensity scale tell us about an earthquake?

how intense an earthquake feels

What information is used to establish the lower numbers on the Modified Mercalli Intensity scale.

how the earthquake is felt by people in an area

Where does most terrane accretion occur?

in association with a continental-oceanic subduction zone

Earth's core is interpreted to consist mainly of ________.

iron and nickel

What kind of fault is illustrated in this figure? E

left-lateral fault

The phenomenon of transforming a somewhat stable soil into mobile material capable of rising toward Earth's surface is called ________.

liquefaction

What kind of fault is illustrated in this figure? A

normal fault

The collective term for any process that produces a mountain belt is called ________.

orogenesis

The ________ is a layer in Earth's interior that is in a liquid state.

outer core

What kind of fault is illustrated in this figure? B

reverse fault

What kind of fault is illustrated in this figure? D

rightt-lateral fault

Our greatest source of knowledge about Earth's interior comes from ________.

seismic waves

The record of an earthquake obtained from a seismic instrument is a(n) ________.

seismogram

A ________ is an instrument that is used to record earthquake vibrations.

seismograph

Which type of force is responsible for normal strike-slip formation?

shear force

Which type of fault has NO vertical motion of rocks associated with it?

strike-slip fault

On a typical seismogram, ________ will show the highest amplitudes.

surface waves

What do we call seismic waves that are transmitted along the outside of Earth?

surface waves

Which kind of seismic wave is responsible for the most shaking (and thus, the most damage to human structures)?

surface waves

What type of structure is shown in the photograph?

syncline

Which type of force is responsible for normal fault formation?

tensional force

A crustal block bounded by faults whose geologic history is distinct from the histories of adjoining crustal blocks is called a(n) ________.,

terrane

What are rocks below and above a fault called?

the footwall below and the hanging wall above

Which of the following does moment magnitude measure or estimate?

the total energy released during an earthquake

What kind of fault is illustrated in this figure? c

thrust fault

Which hazard generated by earthquakes can be destructive many hundreds of kilometers away from the epicenter?

tsunamis

Which of the following does not determine the amount of destruction caused by seismic shaking?

type of fault

A Richter magnitude 8 earthquake is ________ times greater than a Richter magnitude of 7.

10

In the seismograph shown above, what is the estimated time interval between points A and C?

5 minutes

motion that involves oscillation perpendicular to the direction of propagation; only passes through solids,

S waves

motion at Earth's surface that may move materials side to side, or up and down

Surface waves

Why are terranes added to continental margins, rather than subducting under them?

Terranes are too buoyant to subduct.

Which layer is indicated by the letter A in the diagram and what is its composition?

The crust. It has two main subtypes, the continental crust is granitic in composition and the oceanic crust in basaltic in composition.