geoscience midterm

According to wegener’s hypothesis of continental drift, all continents were once attached and formed a single landmass that he called ___, He thought that this land mass survived until about the middle of the ** era

pangea / mesozoic

what is the relationship between the coastlines on the east side of the atlantic and those on the west side?

Continents on the east side could fit snugly against those on the west.

Which of the following statements about wegener’s reconstruction of late paleozoic pangea is true?

Areas glaciated during late paleozoic laid over the south polar region at the time

When wegener compared rock units how exposed on different continents bordering the Atlantic, what did he discover?

Fossils of identical land dwelling species occur on continents that are now separated from one another by the ocean

When wegener compared rock units now exposed on different continents bordering atlantic, what did he discover?

fossils of identical land dwelling species occur on continents that are now separated from one another by the ocean

Why did most geologists initially oppose wegener’s hypothesis of continental drift?

wegener could not explain how or why continents move

keeping in mind shape of magnetic field lines in space around earth, what is true?

Magnetic inclination is approx 0º at equator and 90º at poles

Why can samples of basalt exhibit paleomagnetism?

dipoles of tiny magnetite grains in basalt align with the earth’s field as the basalt cools and stay that way once the basalt is cold.

Today, what is the favored explanation of appareny polar wander paths?

Continental drift with respect to relatively fixed magnetic poles

When a magnetometer is towed over a positive marine mgnetic anomaly…

The measured magnetic field is stronger than expected

Studies of sea floor bathymetry demonstrate that

deep ocean trenches, the deepest of which have a depth of about 11 km, border chains of active volcanoes

Where is the heat flow of oceanic crust the greatest?

along the axis of the mid ocean ridges

Which of the following statements about earth’s magnetic field is correct?

The polarity of the magnetic field reverses every now nad then

A lihtospheric plate consists of

The crust and uppermost part of the mantle

What defines the location of plate boundaries?

The location of abundant earthquake epicenters

What is the difference between a passive continental margin and an active continental margin?

Passive margins are not plate boundaries, whereas active margins are

In the atlantic ocean, where does the youngest oceanic crust occur

adjacent to the mid ocean ridge

In which of the following pairs of terms does the second term represent the type of process that happens at the first term?

Mid ocean ridge / sea floor spreading

Which of the following processes happens at the axis of a mid ocean ridge?

all of the above (molten rock, mineral saturated water, stretching force)

Which of the following statements about a hot spot track is correct?

The youngest volcano of the track occurs at one end of the track

At a (blank), continental crust is being stretched apart. As a consequence, the crust becomes (blank) and volcanoes erupt

Rift / thinner

Why can’t continental crust be subducted?

Too buoyant and can’t sink into asthenosphere

Which of the following statements concerning the forces that drive plate motions is correct?

Ridge push and slab pull forces have the greatest influence on the velocity of plate motion

The character of a lava flow depends on the viscosity of the lava erupted. (blank) lava is less viscous than (blank) and thus flows out as (blank)

basaltic / rhyolitic / thin sheet

Volcanic ash consists of

tiny shards of glass

An avalanche of hot ash is flowing down the flanks of a volcano is known as

pyroclastic flow

What type of pyroclastic debris builds a streamlined form, as show by the image?

a bomb

A large, cone shaped volcano consisting of alternating layers of ash and lava is a

stratovolcano or composite volcano

If a volcano is erupting a gassy, felsic magma, then it is more likely to be (blank)

an explosive eruption

which of the following is not a hazard related to volcano eruptions?

heat wave

What measurable clues indicate that a particular volcano may erupt in the near future?

The volcano changes shape as the magma chamber fills

What is NOT a functional protection or mitigation effort to prevent volcanic hazards?

prediction of exact timing or style of the eruption

Mafic lava erupted at submarine volcano will produce

pillow basalt

which statement is NOT correct

aerosols from volcanic eruptions may be a cause of global warming

Mt. St. Helens erupted in 1980, sending out gas and pyroclastics. Geologists have found evidence of many eruptions of St. Helens, dating back 37,000 years. The mountain is huge and is composed of layers of lava and pyroclastics. Which of the following is most likely true?

It’s a stratovolcano (or composite cone)

Rhyolite lava…

all of the possible answers are correct

Lava is the greatest volcanic hazard to human life because it travels so fast

False, lava is not the greatest threat to human life

The point on the surface of the earth that lies directly above the place where a slip on a fault occurs is the

epicenter

On a (blank) fault, the hanging wall block slips down the surface of the fault, relative to footwall. If the fault displaces the ground surface, a (blank) develops

normal / fault scarp

According to the elastic rebound theory of earthquake generation…

a rock bending elastically before breaking; the sudden break and or frictional sliding causes earthquakes

which of the following is the correct sequence of seismic waves that will be recorded at a distance from the epicenter?

P waves, S waves, surface waves

A mechanical seismograph consists of a pen attached to a suspended weight, and a rolling drum with paper attached. During an earthquake,

the weight stays fixed in space, while the drum and the paper move

To locate the epicenter of an earthquake, what information do you need?

The difference in the arrival times of the P- and S- waves, as recorded at three different stations

The “intensity” of an earthquake…

is defined by the amount of damage caused by the earthquake

A magnitude 4 earthquake results in ground motion that is (blank) the ground motion that occurs during a magnitude 2 earthquake, and releases approximately ____ the amount of energy

100x / 1000 x

Which statement about the distribution of earthquakes on Earth is correct?

Earthquakes occur in discrete belts, along plate boundaries

Which statement about the distribution of earthquakes at convergent plate boundaries is correct?

Hypocenters occur in the Wadati-Benioff zone, down to a depth of about 670 km below the surface

All else being equal, which building would more likely survive a large earthquake?

One whose foundation is built on an exposure of granite bedrock

Tsunamis can be caused by

earthquakes at subduction zones

In the context of geology, a “joint” refers to

a natural crack, on which there has been no sliding, in rock

Both normal faults and reverse faults are considered to be ___ faults. The hanging wall block of a normal fault slides ___ the surface of the fault

dip-slip / down

The fault shown in the above diagram is a vertical surface, and the slip lineations on it are horizontal. What type of fault is it?

strike slip

The type of deformation does NOT depend on

Grain size

Major weather events such as hurricanes and tornadoes release as much energy as the great earthquakes

False. they do not.

A tsunami…

may be just a low and very broad wave at sea, but both slows in speed and grows in height as it approaches shore

If a rock undergoes enough stress to produce elastic strain, an earthquake always happens.

False. an earthquake does not always happen.

Geologists distinguish among different kinds of downslope movement based, in part, on

rate of movement

The gradual downslope movement of surficial sediment or soil in a temperate climate is called ___. If such movement occurs in the tunrdra, where it is permafrost, it is called ___

creep / solifluction

If the water table beneath a hill rises, because of either heavy rain or the impounding of a reservoir,

adjacent slopes become more unstable (because detachment surfaces become weaker)

Downslope movement can be triggered when

downslope forces exceeds resistance force

In a typical slump, the glide surface (slip surface) is ___, and at the uphill end, a ___ formes

curving (spoon shaped) / head scarp

Which of the following will increase the potential for mass movement on a slope?

deforestation

_____ in sedimentary rock may become a failure surface

Bedding plane

The principal difference between a debris slide and a debris avalanche is the _____

degree to which the displaced material remains internally coherent

The main difference between a slump and a debris slide is the ____

shape of the path taken by the moving mass

to a geologist…

all landslides are mass movements, but not all mass movements are landslides

moisture among sediment grains…

can promote stability if present in small amounts, but promotes mass wasting if sediment is saturated

which of the following factors decreases the risk of mass movements

adding vegetation to the side of the hill

slow downhill movement of regolith creep is due to

expansion and contraction

submarine landslides are…

responsible for catastrophic tsunamis

geologic mapping can identify regions at landslide risk by

identifying past failures and detecting slow movements