geol 101 exam 2

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At what depth do rocks begin to ductilely deform in response to stress rather than brittlely deform?

15 km

Shale is metamorphosed into three rock types: (1) a banded gneissic rock; (2) a rock with small mica crystals with a shiny aspect; (3) a very shiny rock with large mica crystals; and (4) a dull slate with cleavage. Which of the following lists these rocks in order of increasing metamorphic grade?

4, 2, 3, 1

On this figure of Bowen's Reaction Series, which mineral would crystallize last from magma?

4, K-feldspar

How much silica do mafic rocks contain?

44-55%

In what site on this figure would you expect high pressure/low temperature metamorphism?

A and B

Flood basalts influence life on Earth because

All of these choices are correct. (large volumes of flood basalts are erupted during a short time; eruptions can release large amounts of gas that cool the atmosphere; eruptions can release large amounts of gas that warm the atmosphere.)

Which of the following are true of felsic magmas?

All these are true of felsic magmas.

Which of the following activities is NOT used to monitor volcanoes?

All these are used to monitor volcanoes.

What is the role of pressure in melting?

At higher P higher T is required for melting and vice versa

In what site on this figure would you expect low pressure/high temperature metamorphism?

C

What is the typical relationship of cleavage to folds?

Cleavage is usually parallel to the axial surfaces of folds

Based on the image and your knowledge of metamorphic minerals, which of the following is true?

Garnet is diagnostic of moderate- to high-grade metamorphic conditions

Which of the following is a good interpretation of the environmental significance of an attribute of a sedimentary rock?

Graded beds indicate that the strength of the current decreased through time.

How does the addition of water cause melting?

It changes the location of the liquid-solid boundary.

The largest concentration of composite volcanoes on Earth is located along the

Pacific Ring of Fire.

How are fissures formed?

Pressure from magma pries open fractures in rock, and then magma fills the fracture.

In this section, a lower gray rock is successively overlain by beach sandstone, lagoon mudstone, and limestone. What is the best interpretation of what was going on?

The area was experiencing a transgression

What typically happens to the size, shape, and sorting of clasts as they are transported from steep mountains toward more gentle settings?

The clasts become more rounded.

How would the force and stress on the wooden pillar in this figure change if the stone weight was the same size but the wooden pillar were narrower?

The force would remain the same, but the amount of stress would increase.

What does this texture indicate about the formation of this rock?

The magma had abundant dissolved gas

What can you infer from this contact between an overlying conglomerate and underlying sandstone?

There was an abrupt event, such as a flood

Which of the following is NOT true about flood basalts?

They are fed from large interconnected composite volcanoes.

Which of the following is NOT a characteristic of a volcanic dome?

They are one of the largest types of volcanoes.

Which of the following are ways that viscosity affects gases in magma?

Viscous magma prevents gas from escaping easily.

A graded bed forms due to:

a gradual decrease in the strength of the current over time.

What type of volcanic eruption is shown in this photograph?

a pyroclastic column

If you were designing a rock that resisted weathering, which of the following characteristics would it have?

a quartz-rich rock

The most likely cause of graded bedding found in sedimentary rocks is:

a reduction in water current velocity.

An ophiolite is

a sliced-off piece of oceanic crust that has been thrust onto the edge of a continent or island.

Loose sand on the continental shelf or shelf slope that becomes unstable and flows downslope as a thick slurry of sediment and water is known as:

a turbidity current.

Which of the following is the best indicator that a volcano might be very dangerous?

a volcano that contains andesite and welded tuffs

All the following are tectonic settings where large magma chambers can form except

above existing lava fields

How does chert form?

accumulation of silica-rich organisms or mixing of seawater and groundwater

Bedding in sedimentary rocks is defined by:

all of the currents listed

The main source of heat energy for Earth's interior is a direct result of

alpha decay, which is an unstable atom losing 2 protons and 2 neutrons.

The most common volcanic rock found in lava flows on composite volcanoes is

andesite

What type of structure is shown in this figure?

anticline

A fine-grained mafic igneous rock is called

basalt

What type of volcanic eruption is probably shown in this photograph?

basaltic lava flow

If bubbles cannot escape easily from a magma, the resulting eruption is likely to

be explosive

What type of metamorphic feature is shown in this photograph?

cleavage

A relatively large, symmetrical volcano that contains interlayered lava flows, pyroclastic deposits, and volcanic mudflows is a

composite volcano

What kind of metamorphism is occurring in this setting as indicated?

contact

What is the typical setting for fold and thrust belts?

convergent plate boundaries

The igneous feature shown in this figure is a

dike

An igneous rock that solidifies on Earth's surface is a(n)

extrusive rock

This igneous rock is

felsic and coarse-grained.

This igneous rock is

felsic and fine-grained

What types of rocks would be most common in the volcano in this photograph?

felsic and intermediate lava flows and tephra

The deep-sea floor is characterized by sediment dominated by

fine dust and the remains of single-celled organisms.

Shield volcanoes commonly involve

fluid lava flows

What type of metamorphic feature is shown in this photograph?

foliation in banded gneiss

When basaltic lavas reach the ocean they

form pillow basalts

Which of these attributes preserved in sedimentary rocks gives us the most information about past climates?

fossils

Which of the following is NOT a rock typically found within calderas?

gabbro

A coarse-grained intrusive igneous rock composed mostly of feldspar and quartz is called

granite

A nonfoliated metamorphic rock not created by pressure or differential stress but by being baked by an igneous intrusion is a

hornfels

Under what conditions was this rock likely deformed?

hot and deep

The geothermal gradient is the

increase of Earth's temperature with increase in depth.

A mantle plume rises because

it is solid but less dense than material around it.

What is decompression and what happens when a rock decompresses?

it melts

What types of structures are shown in this photograph?

joints

The igneous feature shown in this figure is a

laccolith

A sinkhole is most likely to form from dissolution in:

limestone

Long, thin lava flows are typically produced by:

low-viscosity lavas

An igneous rock rich in olivine and pyroxene is classified as __________ in composition.

mafic

According to the fossil record, what events have coincided with the approximate times when flood basalts were erupting?

mass extinctions

What type of structure is shown in this figure?

monocline

What is the most likely change to this rock in response to metamorphism without deformation?

new minerals will grow

This photograph shows an iron formation. How does it form?

precipitation from seawater early in Earth's history

Cause of Temperature variations?

radioactive decay

The transition from the gray shale and limestone to the sandstone and breccia above represents a:

regression

The main cause of melting along subduction zones is the

release of water from the subducting plate.

This image is demonstrating chemical __________ during metamorphism and deformation.

remobilization

What type of fault is shown in this figure?

reverse fault

What type of rock would you form in this environment, showing a dried up lake bed?

rock salt and other evaporite minerals

The main way water gets into a subduction zone is by

seawater introduced into oceanic crust at the mid-ocean ridge, prior to subduction.

A graywacke is a type of

siltstone

The special geologic terms used to represent the direction of a horizontal line on an inclined surface (like in a fault) and the angle of that surface to the horizontal are

strike and dip

What is the plate-tectonic setting of Mount Rainier?

subduction beneath the Pacific Northwest

If a rock is subjected to differential stress, then it means that

the amount of stress is greater in some directions than in others.

Imbricated clasts in this river means that:

the current flowed from right to left

A lava solidifies into nonvesicular basalt instead of vesicular basalt because

the lava has low gas content

Which of the rock layers in this figure was most likely deposited by sand dunes on land?

the lowest red sandstone

The higher the gas pressure builds in a magma

the more explosive an eruption it is likely to produce.

A finely crystalline or glassy igneous texture indicates that

the rock cooled quickly

A porphyritic igneous texture indicates that

the rock cooled slowly and then quickly

A vesicular igneous texture indicates that

there was a lot of gas in the magma

Which way was the current (either wind or water) moving during deposition of this section of rocks?

toward the right

Downslope marine flows comprised of mixed masses of sand, mud, and water are called

turbidity currents.

Which of the following units was most likely deposited in the deepest marine water?

unit 5

What type of basaltic feature is shown in this photograph?

vesicles

Changes in topography, water chemistry, and gas output all are used to help predict

volcanic eruptions

The relationship between weathering and erosion can best be characterized as

weathering loosens material before erosion carries it away, but erosion can also scour and move unweathered material.

Which of the following attributes does NOT apply to these sediments?

well sorted

Columnar joints, such as the ones shown in the photograph, are formed

when hot but solid igneous rock contracts.

Role of water in melting? Does it help in melting?

yes


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