geol 101 exam 2
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