Geo Exam 3

The primary proponent of the idea of continental drift was _______ ________.

Alfred Wegener

Ancient glacial deposits in the southern hemisphere reveal that portions of __________, ___________, ____________, and ______ were once grouped together near the _____ _____ with Antarctica.

Australia; India; Africa; South America; South Pole

Oceanic crust is

Basaltic

_____________ is the movement of sediment in a zigzag pattern along the beach, caused by the swash and backwash of water from each breaking water.

Beach drift

Many beaches in _________ are narrower than they were even a few years ago.

California

Two features in the United States produced when oceanic & continental crust collide include the __________Range and the considerably older _________________ mountains.

Cascade; Sierra Nevada

How does the type of land material affect the amount of destruction caused by an earthquake?

Different materials vibrate for different periods of times

T/F Normal faults indicate compressional forces are at work, while reverse faults result from tensional forces.

False

T/F When rock deforms plastically, it ruptures.

False

If a 20 mph wind steadily blows from the northwest over Lake of the Woods and over Lake Bemidji, which lake will produce the largest waves and why (use the proper term).

Lake of the Woods; it has a larger fetch

___________- refers to the movement of sediment parallel to the shoreline, within the surf zone

Longshore drift

To classify the damages following an earthquake, the U.S. Coast and Geodetic Survey uses the ________ scale.

Mercalli

The plate boundary in the Atlantic Ocean is called the ___________ __________.

Mid-Atlantic Ridge

Name (give the location of) two divergent plate boundaries.

Mid-Atlantic Ridge and the East Pacific Ridge

Are the Hawaiian Islands an island arc? Explain.

No because they results from hot spots, not oceanic-oceanic convergence

The east coast is situated midway within the _____________

North American Plate

The Hawaiian Island-Emperor Seamount Chain formed as the _________ plate slowly migrated over a ___________ hot spot.

Pacific; stationary

Which is the longest barrier island in TX, and how long is it?

Padre Island; 113 miles.

What denotes the global distribution of earthquakes?

Plate tectonics

The ________ scale classifies the recorded magnitudes of earthquakes on a logarithmic scale.

Richter

________ travel by shaking particles at right angles to the direction of wave travel

S-waves

The______ fault in California lies along a _______ boundary.

San Andreas; transform

________ are sites for potential major earthquakes in the near future

Seismic gaps

Give 3 examples of where both oceanic and continental crust contained within the same lithospheric plate

South American plate, African plate, North American plate

Is it true that some types of ground actually amplify the motion initiated by seismic waves? When is it most amplified?

Yes; when the material has a natural frequency matching the seismic wave

Barrier islands are only ______ kilometers wide, at most.

a few

Rank the following types of buildings according to susceptibility to earthquake damage: steel, wood, reinforced masonry, unreinforced masonry, and adobe

adobe, unreinforced masonry, reinforced masonry, wood, steel

Strong evidence for the Hawaiian Island-Emperor Seamount Chain being over a stationary hotspot is the observation that the ____ of the islands and the seamounts _______ progressively along the chain

age; increase

In the outcrop pattern, where are the oldest rocks found where an anticline has been eroded to flatness at Earth's surface?

along the axis

Magnitude is determined by measuring the _________ (height) of seismic waves.

amplitude

Linear upfolded structures with the oldest strata in the center are termed

anticlines

Rock folds in the shape of arches are known as ___________, while folds in the form of troughs are known as _____.

anticlines; synclines

Where two sea caves unite, a sea ______ is produced.

arch

Which way do the limbs of the anticline dip—away from the fold axis or toward it?

away

Major geologic activities such as mountain building, volcanism, and earthquakes occur primarily at or near plate ____________.

boundaries

A __________ is an offshore structure built to block incoming waves

breakwater

In _______, sand delivered to the quiet water zone by beach drift or longshore drift accumulates in the now-sheltered area and is not carried through to the other side.

breakwaters

A wave can be thought of as extending beneath the surface, but only to a depth of ____________________.

1/2 wavelength

Waves cannot interact with a bottom deeper than ___________

1/2 wavelength

An earthquake of magnitude 6 is ____ times greater in wave amplitude than one of magnitude 4, but the former earthquake releases ____ times more energy than the latter.

100; 1024

Sea level has risen between ____ and _____ centimeters over the past 100 years.

10; 15

No sediment older than __________ years occurs on oceanic crust, which is further evidence in support of the idea that ______ _____ is continually being recycled into the mantle

180 million; oceanic crust

Using the ages of magnetic reversals we find spreading rates range from __ to __ cm per year

2; 9

About _______ earthquakes occur annually that are strong enough to be felt.

30,000

How many earthquake occur annually that are strong enough to be felt by humans?

30,000

There are nearly _____ barrier islands along the Atlantic and Gulf coasts, from _______ to _________

300; Cape Cop; Padre Island

Each unit of Richter magnitude equates to approximately a ___-fold increase in _____.

32; energy

Some continental crust has been dated at greater than _________________ years, which supports the idea that "______" continental materials cannot subduct back into the mantle.

4 billion; granitic

The bend in the Hawaiian Island-Emperor Seamount chain occurred about _________ years ago when the motion of the plate changed from ________ to a more _____________ path.

40 million; north; northwesterly

At what water depth will a wave with a length of 13 feet first disturb bottom sediment?

6.5 feet

Sea _____ form where waves encounter less durable rocks.

caves

the oldest rocks in the Black Hills (a domal structure in South Dakota) should be located near the ________ of the structure.

center

Where are most the world's earthquakes located?

circum-Pacific belt

The outcrop pattern of a plunging anticline _____________ in the direction of its plunge

closes

Why doesn't the San Andreas Fault slip everywhere along its length during an earthquake

composed of multiple branches/fractures

List the 3 stresses rocks are subject to

compression, tensional, shear

Folding of rocks is the result of ________________ stress

compressional

As the total surface area of Earth must remain ______, new crust generated at _________ boundaries is eventually destroyed at ___________ boundaries.

constant; divergent; convergent

Where oceanic and continental crust converge, sediment carried by the oceanic crust eventually becomes scraped off and added to the mass of the ___________.

continent

Wegener's first piece of evidence for ______________________ was the apparent _______ ___ of the continents

continental drift; jigsaw fit

What type of plate interaction involving what type(s) of crust is producing the Himalayas?

continental-continental convergence

Neither crustal segment will subduct beneath the other when _____________ crust collides with _____________ crust.

continental; continental

In actuality, it is the ______________ that have drifted, while the magnetic pole has remained relatively near Earth's axis of ___________.

continents; rotation

Most geologists think that plate tectonics is driven by some type of thermal __________ in the mantle.

convection

It is important to realize that a single plate can, and normally does, contain both types of ________.

crust

The tallest natural features on barrier islands are _______, formed near the ________ edge where winds have reworked sand grains.

dunes; seaward

During the 1950s and 1960s, detailed mapping of the ocean floor was accomplished by ______

echo sounding

. When a rock is able to return to its original shape after it has been deformed, it is said to have experienced deformation.

elastic

The west coast is called an __________ coast because the land has been uplifted; thus it bears the markers of a ______ drop in sea level.

emergency; relative

The surface location directly above the focus is called the ____________.

epicenter

What do breakwaters and groins cause?

erosion downbeach

Chesapeake Bay is an ___________. It formed as the _______________ River was drowned by a rising sea.

estuary; Susquehannah

Movements of Earth's crust during an earthquake are commonly associated with fractures called ________

faults

List 4 ways earthquakes lead to deaths

fire, tsunamis, landslides, disease

Eventually, rupture will occur at the weakest spot, which is called the ________.

focus

Energy released during an earthquake travels in all directions away from the ______ as _______ ________.

focus; seismic waves

Some evidence for drifting continents included the presence of identical _________ of non-swimming creatures in the rocks of now widely separated continents.

fossils

Rising sea level is expected to continue or even accelerate as a result of both melting of ____________ and _________ of the oceans, in response to global warming.

glaciers; thermal expansion

In a fault, the down-dropped blocks are called ______ and the relatively upfaulted blocks are called _____

grabens; horsts

Continental crust is

granitic

Transform fault boundaries are zones where plates _______ each other.

grind past

Today, the driving force for continental movement is summed up as an unequal distribution of ______ within Earth's mantle.

heat

Swash and backwash is a never-ending process; so grains may be transported up to ________ of meters along a beach in a single day.

hundreds

Waves erode coasts through: 1) the ______ of the wave itself, 2) _______, and 3) _______.

impact; abrasion; hydraulic pressures

The ______ of an earthquake is determined rather crudely using primarily subjective information.

intensity

_________ occurs above a stationary mantle _________ or a hot spot.

intraplate volcanism; plume

Most submergent coasts have a very __________ shoreline. Most emergent coasts develop relatively _________ shorelines.

irregular; straight

Where oceanic crust collides with oceanic crust, the resulting volcanism will produce a volcanic ___________ _____ located away from any continental mainland

island arc

Artificial structures projecting toward the sea at the entrance to harbors or rivers are called _________.

jetties

List a four of the various early evidences supporting the notion that continents have "drifted."

jigsaw fit, fossil match across seas, rock types/geological features, ancient climate

Behind barrier islands is a quiet, shallow water body known as a __________

lagoon

The movement of grains by longshore currents is referred to as _________

longshore drift

What does the word recumbent mean?

lying down

Not all _______ rises along oceanic ridges or above subducted slabs

magma

Sea-floor spreading proposed that rising _________ produces new __________________ at oceanic ridge crests, and that older seafloor is forced to either side, eventually to be consumed back into the ________ at the sites of deep-ocean _________.

magma; oceanic crust; mantle; trenches

When minerals solidify from a melt, they contain a record of the orientation of Earth's _______ _______ at that time.

magnetic field

The magnetic record contained in rocks reveals that the location of Earth's ____________ has changed relative to the continents. The wandering of the poles is only __________.

magnetic poles; apparent

Earthquake ___________ refers to the amount of power released during an earthquake.

magnitude

Crust is recycled back into the __________.

mantle

At depth, a subducted slab begins to _______, producing ________ which rise to eventually produce _________ within the crust, or ________ at the surface.

melt; magmas; plutons; volcanism

A new _______ ________ is formed where the two continental plates meet.

mountain range

Colliding continents are responsible for the formation of new _______ _________.

mountain ranges

Divergent plate boundaries are zones where plates ____

move apart

Convergent plate boundaries are zones where plates ______

move together

does the footwall move in faults?

no

When the rock above a fault plane moves down relative to the rock below, a ______ fault has occurred.

normal

Because most waves do not reach the shore head-on, sand grains are rinsed up a beach at ______ angles to the shore.

oblique

Because of the ______ angle of incoming waves, a current becomes established within the surf-zone ________ to the shoreline. This current is called a ______________.

oblique; parallel; longshore current

The splitting of continental crust both leads to and results from the formation of new ________ ________.

oceanic crust

The pattern of magnetic recording is identical on either side of an ______ ______.

oceanic ridge

Tectonically speaking, what is required in order for deep- and even intermediate-focus earthquakes to occur?

oceanic trenches

What type of plate interaction involving what type(s) of crust is producing the Andes?

oceanic-continental convergence

What type of plate interaction involving what type(s) of crust is producing the Japanese Islands?

oceanic-oceanic convergence

We must consider Earth's surface to be made of two types of crust, ___________ and __________.

oceanic; continental

Where oceanic and continental crust converge (collide), the ________ lithosphere must sink beneath the more buoyant _________ lithosphere.

oceanic; continental

If erosion stripped the top off a dome, one would find the ______ rocks were exposed at the center.

oldest

The outcrop pattern of a plunging syncline ______________ in the direction of its plunge.

opens

The movement of sand from the beach and the dunes into the marshes along the backside of a barrier island during storms is called ________

overwash

__________ travel by compressing particles in the direction of travel of the wave.

p-waves

Body waves are divided into _________ and ____________.

p-waves; s-waves

____ waves are called __________ waves because they arrive first at recording stations.

p; primary

The net transport of beach grains is __________ to the beach, in a zig-zag or stair-step pattern similar, in a way, to what produces creep (mass wasting).

parallel

Where would the older bedrock be, near the center or near the perimeter of the Williston Basin?

perimeter

Most earthquakes are generated by the relative motions of large crustal blocks along _______ _________.

plate boundaries

The west coast is tectonically active because it is situated near a ____________.

plate boundary

Building upon the concepts of continental drift and sea-floor spreading, scientists have developed a more complete and unified model called ________

plate tectonics

The main reason for the difference in the character of the shorelines of the eastern and western United States coasts is related to ____________

plate tectonics

The splitting of continental crust both leads to and results from the formation of new oceanic crust. Colliding continents are responsible for the formation of new mountain ranges. The ideas in these two statements are part of the theory of _______ ________.

plate tectonics

what denotes the global distribution of earthquakes?

plate tectonics

Earth's crust is divided into many separate lithospheric ________ which are able to move as distinct units as they float upon the less rigid ("plastic") material of the ____________

plates; asthenosphere

Breakwaters result in a quiet water zone, which is commonly intended for the ___________.

protection of boats

The bending of waves is called wave __________.

refraction

There are recorded periods of ____ and ______ polarity of Earth's magnetic field.

regular; reversed

Very solid support for the idea of sea-floor spreading is found in the form of _________ preserved in rocks of the sea floor.

remnant magnetism

Echo sound mapping revealed the presence of a great oceanic __________ system near the middle of ocean basins and deep-sea _________ close to the margins of the oceans.

ridge; trenches

When spreading actually begins, the crust sinks through normal faulting, to produce a ____ ________.

rift valley

A central ____________was discovered along the length of the Mid- Atlantic _________, suggesting that _____________ forces were at work.

rift valley; Ridge; tensional

Name four types of rocks that will bend even under low levels of stress.

rock salt, shale, limestone, schist

Some evidence for drifting continents included the presence of similar ______ ______ and similar geologic structures at the locations where the shapes of continents had earlier suggested a fit.

rock types

____ waves are not transmitted through fluids, which is how we know Earth's outer core is ______.

s; liquid

____ waves are called ___________ waves because they arrive later.

s; secondary

At jetties, since the supply of ______ has been _______ to downbeach areas, they are subject to erosion, without redeposition, by waves and beach drift

sand; cut off

Groins deprive down beach areas of _______, so property owners there, in sequence, deploy their own __________.

sand; groins

Jetties are intended to interfere with the movement of ______ and to funnel ____________ to scour and deepen channels for ship traffic.

sand; wave energy

Cliffs produced by slippage along faults are referred to as ________.

scarps

If spreading continues, a new linear _____ will be produced.

sea

When a sea arch collapses, an isolated _______ might remain.

sea stack

A quiet zone within a seismic belt is called a ______________.

seismic gap

Only ________ ______ earthquakes occur along oceanic ridges

shallow focus

Many _______ focus earthquakes occur in the middle of the oceans, at locations coinciding with the _______ ______ system. Still other earthquakes occur within active mountain belts such as the ________.

shallow; ocean ridge; Himalayas

What type of stress (from question 3 above) produces the San Andreas Fault?

shear

When a wave does "feel the bottom", it _______ _____. This allows more seaward waves to ________ ____.

slows down; catch up

An extension of a beach part way into a bay is called a _______

spit

Divergent Thse boundaries are typically referred to as ____________ centers

spreading

Refraction concentrates wave energy upon the protruding portions of irregular coastlines, with the result that erosion tends to eventually ___________ such coasts.

straighten

_____ is the distortion or change in shape that results from stresses in rocks

strain

Stress buildup will cause rocks to ______ (bend) in an initially _________ manner.

strain; elastic

The compass direction of a line defines the _________ of the plane

strike

The general name for faults having primarily horizontal movements is

strike slip

A ____________________ fault's displacement is parallel its strike.

strike-slip

A ___________ zone will also form where oceanic crust collides with oceanic crust.

subduction

The site of crustal descent into the mantle is called a ___________ ______.

subduction zone

The east coast is called a ______________ coast because the land was covered by a rise in sea level following the retreat of ________________ ice sheets.

submergent; Pleistocene

An incoming wave that has felt bottom breaks in a region referred to as the _____ ______.

surf zone

_________ waves cause the greatest amount of destruction

surface

Seismic waves that are transmitted (propagated) along the surface are called ________ ________

surface waves

The motion of a sheet of water up a beach is called ________, and the return of that water back down the beach is called __________.

swash; backwash

Most earthquakes result from the gradual buildup of stress due to _______ forces.

tectonic

Only _________________ stresses could have produced such a series of fault-block mountains

tensional

With what type of stress does a block of rock slide down in the middle

tensional

Why are the oldest rocks in Iceland at the extreme eastern and western ends of that island?

the oldest sediment is the furthest distance from the ridge dividing Iceland

Why are sea cliffs common along the west coast of North America but uncommon along the east coast?

the west coast is tectonically active and the east coast is tectonically passive.

why are seismic gaps probable sites for stronger than average earthquakes?

they are storing strain

Oceanic & continental crusts vary in _______, but also in the type of ____ that comprise them.

thickness; rocks

In a near-surface environment, is granite more likely to bend or to break?

to break

Along an irregular coastline, waves are refracted __________ (toward, away from) headlands or promontories.

toward

Which way do the limbs of the syncline dip—away from the fold axis or toward it?

toward

In the outcrop pattern, where are the oldest rocks found where an syncline has been eroded to flatness at Earth's surface?

toward the limbs

Places where two plates slide past each other are called ___________ boundaries.

transform

If wave action noticeably has ________ a cliff, the overhanging cliff will eventually collapse.

undercut

What direction does the hanging wall move in a reverse fault?

up

dip-slip faults are classified as reverse faults when the hanging wall block moves _______ relative to the footwall.

up

An earthquake is any __________ of Earth caused by a rapid release of __________.

vibration; energy

Andes are an example of a __________ _____ produced when oceanic & continental crust collide.

volcanic arc

Eroded debris may accumulate at the seaward end of wave-cut platforms, producing an extension called a __________

wave-built terrace

Rocks below wave base are of course left in place, so that a ________ _________ is left behind as a wave-cut cliff retreats landward.

wave-cut platform

Grass-covered wave-cut platforms are called ________

wave-cut terraces

A ________ moves forward, but the ________ within it does not.

wave; water

The distance between successive wave crests (or any successive equivalent parts of a wave) is called the ___________.

wavelength

The result of slowing down & catching up of waves as they feel bottom is a decrease in __________, and a buildup in wave _________.

wavelength; height

All water waves other than tsunamis are produced by the _______.

wind

The amount of energy thus delivered to the water depends upon what three factors?

wind speed, wind duration, fetch

Scientists presently have some ability to predict earthquake locations and magnitudes, but can only predict the time for earthquakes within a range of ________________.

years or decades

Minerals can be used as fossil __________.

compasses

Name 3 barrier islands along the Texas coast.

Galveston, Brazos, Mustang

________ are structures built specifically to trap sand to widen a beach.

Groins

Who proposed the "sea-floor spreading" theory?

Harry Hess

Explain the origin of the Hawaiian Island-Emperor Seamount Chain.

Hot, rocky plume ascended through the mantle and dropped the confining pressure, causing decompression melting. As a result, a hotspot (an area of volcanism) appeared on the surface, involving crustal lifting, and the Pacific plate moved over the hot spot and built the Chain. The plume is long-lasting and stationary.

What plate lies just west of the state of Washington in the United States? What type of boundary does it make with the state of Washington?

Juan de Fuca plate; transform boundary

To what plate does Australia belong?

The Australian-Indian plate

How does the watering of lawns by people living atop sea cliffs along the U.S. Pacific coast affect the stability of those cliffs?

The elevated water table causes water to seep out of the cliff face, loosening grains and cutting the slope

T/F When older rocks overlie younger rocks, it may indicate that thrust faulting has taken place.

True

What is an estuary?

Where the river meets the sea

The largest shoreline features that are maintained solely by beach drift and longshore drift are called ________ _______.

barrier islands

A beach that extends completely across a bay is called a ___________ _____.

baymouth bar

Beaches commonly extend into or across _______ where grain migration is ________.

bays; active

The net movement of grains on a beach is called _______ _______.

beach drift

Barrier islands are maintained solely be _______ and _________

beach drift; longshore drift

Together, ________ and ________ supply sand to many regions that would otherwise be nearly sandless.

beach drift; longshore drift

Most earthquakes occur in ___ or ____, with the greatest amount of activity occurring along the borders of the _______ _______.

belts; zones; Pacific Ocean

A wave ______ when part of it "feels" the bottom before the rest of it does.

bends

Seismic waves that travel through Earth's interior are called ______ ______.

body waves

Beaches in Cali have been narrowed because sea level rise, but another is the interruption of sand supply from rivers because of the construction of ________.

dams

How do dams on rivers affect coastlines?

dams trap the sand; increased erosion

Wave water moves in circular orbits which steadily _________ in diameter downward because of energy losses due to friction.

decrease

__________, intermediate, and ________-focus earthquakes occur in association with deep-sea _______.

deep; shallow; trenches

___________ is defined as the angle of inclination of the plane measured perpendicular to the strike.

dip

When describing the orientation of a fault plane, the angle of inclination of this surface is termed

dip?

Fetch is the ________ the wind blows over open water.

distance

A single seismograph station can determine the ____________ to an earthquake epicenter, but ________ seismograph stations are needed to determine the ___________ of that epicenter

distance; 3; location

_____________ boundaries occur where plates spread apart

divergent

A recently formed __________ boundary separating Arabia from Africa is producing the still-widening ____ ____.

divergent; Red Sea

One of the earliest signs of the splitting apart of a continent includes uplift called _______ , with associated _______ cracks and perhaps volcanism.

doming; tensional

Dip-slip faults are classified as normal faults when the hanging wall block moves _______ relative to the footwall.

down

What direction does the hanging wall move in a normal fault?

down

The direction of backwash is ALWAYS directly __________-

downslope

One of the main objections to Wegener's hypothesis was the lack of a suitable _________ _________ for the movement of continents.

driving mechanism