GPY113 chap 9
Put the events in order (from top to bottom) that describe the eruption of Mount St. Helens in May 1980.
1. an earthquake occurred2.an avalanche released pressure in the magma chamber3.the volcano erupted in a lateral blast4.a pyroclastic flow swept down the mountain5.a column of ash rose 25km into the air
Gas lines that are ruptured during earthquake shaking often cause
fires or explosions
Basaltic lava is not very viscous, so it ______ after erupting from a vent or a fissure (crack).
flows downhill
An image similar to this one was created after the 1964 Alaskan earthquake at a time before plate tectonics was an accepted science. Looking at this image, we now can clearly see the area is a zone, with the ocean crust moving underneath the North American continent.
subduction
The higher the gas pressure builds in a magma, ______.
the more explosive an eruption it is likely to produce
Put the events of caldera formation in order. Begin with the first event (at the top) and end with the last.
1. underyling 2. magma 3. overlying .4 small valvanic
As shown by the number of ash beds in the image, over the past 2.1 million years, Yellowstone has experienced ______ huge caldera-forming eruptions, which spread ash over most of the western half of the United States.
3
Match the basin with the description of how it formed.
A matches Choice, A block dropped down on a normal fault. A block dropped down on a normal fault. B matches Choice, A thrust sheet pressed down the crust. A thrust sheet pressed down the crust. C matches Choice, Horizontal motion was accompanied by a block down-dropping. Horizontal motion was accompanied by a block down-dropping.
Match the type of differential stress with the appropriate image.
A matches Choice, Compression Compression B matches Choice, Tension Tension C matches Choice, Shear Shear
Based on the map, what is true regarding earthquakes in the locations indicated? (Yellow dots = shallow-depth earthquakes; green dots = intermediate; red dots = deep.)
A matches Choice, Mostly shallow earthquakes occur along the mid-ocean ridge. Mostly shallow earthquakes occur along the mid-ocean ridge. B matches Choice, This is a diffuse zone of seismic activity associated with continental rifting. This is a diffuse zone of seismic activity associated with continental rifting. C matches Choice, This is a large zone of seismicity associated with a continental collision. This is a large zone of seismicity associated with a continental collision. D matches Choice, Shallow, intermediate, and deep earthquakes occur along a subduction zone. Shallow, intermediate, and deep earthquakes occur along a subduction zone. E matches Choice, Very little seismicity occurs in this area, which is far from a plate boundary. Very little seismicity occurs in this area, which is far from a plate boundary.
Match the location with the best description for earthquakes formed in that area within a continent.
A matches Choice, Strike-slip motion mostly causes shallow earthquakes; some may be large. Strike-slip motion mostly causes shallow earthquakes; some may be large. B matches Choice, Moderate-size normal-fault earthquakes are created at a rift. Moderate-size normal-fault earthquakes are created at a rift. C matches Choice, Magma intrusions may cause small earthquakes as molten material moves through rock. Magma intrusions may cause small earthquakes as molten material moves through rock. D matches Choice, Preexisting faults readjust and move as the plate is subjected to new stresses; may produce large earthquakes. Preexisting faults readjust and move as the plate is subjected to new stresses; may produce large earthquakes.
Based on this map, what is true regarding earthquakes in the locations indicated? (Yellow dots = shallow-depth earthquakes; green dots = intermediate; red dots = deep.)
A matches Choice, Subduction zone causes earthquakes along the Aleutian Islands. Subduction zone causes earthquakes along the Aleutian Islands. B matches Choice, Most earthquakes occur due to volcanic activity. Most earthquakes occur due to volcanic activity. C matches Choice, Strike-slip earthquakes are common along the San Andreas fault. Strike-slip earthquakes are common along the San Andreas fault. D matches Choice, Shallow earthquakes follow the Mid-Atlantic Ridge. Shallow earthquakes follow the Mid-Atlantic Ridge. E matches Choice, Shallow, intermediate, and deep earthquakes occur along this subduction zone. Shallow, intermediate, and deep earthquakes occur along this subduction zone.
Match the location on the image with the best description for causes of earthquakes in that location.
A matches Choice, The oceanic plate is bent and stressed as it moves toward the trench. The oceanic plate is bent and stressed as it moves toward the trench. B matches Choice, Shearing occurs within the accretionary prism. Shearing occurs within the accretionary prism. C matches Choice, Magma is moving. Magma is moving. D matches Choice, Shearing and downward-pulling forces produce deep earthquakes. Shearing and downward-pulling forces produce deep earthquakes. E matches Choice, Compressive stresses associated with plate convergence cause thrust faulting behind the magmatic arc. Compressive stresses associated with plate convergence cause thrust faulting behind the magmatic arc.
Match the location on the image with the best description for causes of earthquakes in that location.
A matches Choice, Thrust faults form near the plate boundary and create large, shallow earthquakes. Thrust faults form near the plate boundary and create large, shallow earthquakes. B matches Choice, Megathrust forms along the plate boundary and creates large earthquakes between the two plates. Megathrust forms along the plate boundary and creates large earthquakes between the two plates. C matches Choice, Thrust faults or reactivated older faults may form within the interior of either continent. Thrust faults or reactivated older faults may form within the interior of either continent. D matches Choice, Oceanic plate material is detached, and deep earthquakes cease. Oceanic plate material is detached, and deep earthquakes cease.
Match the joint type with the correct image.
A matches Choice, Vertical joints Vertical joints B matches Choice, Columnar joints Columnar joints C matches Choice, Unloading joints Unloading joints
What is an intrusion?
A magma body that solidifies at depth
Which event triggered the eruption of Mount St. Helens in May 1980?
An earthquake that caused a landslide
A fold in which rock layers warp up in the shape of an A is a(n) , whereas a fold in which rocks fold down in the shape of a U is a(n)
Blank 1: anticline Blank 2: syncline
Sheetlike intrusions of magma that cut across existing layers are ; sheetlike intrusions that are parallel to surrounding rocks are
Blank 1: dikes Blank 2: sills
The formation of a caldera begins as magma fills a large magma chamber. Eventually, the magma erupts as columns and flows of pyroclastic material. The magma chamber is emptied and leaves behinds a large, steep-sided, circular feature that may have volcanic within it.
Blank 1: felsic or viscous Blank 2: domes
A composite volcano consists of layers of lava flows, flows, and deposits of mudflows and
Blank 1: pyroclastic Blank 2: landslides or ash
How does volcanism create local mountains?
By piling up different types of lava and pyroclastic debris
Which of the following accurately describe a cinder cone?
Form in a short amount of time Composed of a pile of loose rock fragments Created by basaltic lava fountains
Which of the following lists the four types of volcanoes shaped like hills and mountains?
Cinder cone, shield, composite, dome
Which of the following are forms of differential stress?
Compression Shear Tension
Match the location on the image with the best description for causes of earthquakes in that location.
D matches Choice, Spreading and slip occurs along normal faults; also intrusion of magma into fissures. Spreading and slip occurs along normal faults; also intrusion of magma into fissures. B matches Choice, Strike-slip earthquakes occur along faults that link adjacent segments of the spreading center. Strike-slip earthquakes occur along faults that link adjacent segments of the spreading center. C matches Choice, Plate cools, subsides, and bends as it moves away from the ridge; stress from the bending forms steep faults. Plate cools, subsides, and bends as it moves away from the ridge; stress from the bending forms steep faults. A matches Choice, Rocks here flow because they are too hot to fracture; earthquakes are small and numerous. Rocks here flow because they are too hot to fracture; earthquakes are small and numerous.
What is the primary difference between dikes and sills?
Dikes are intrusions that cut across existing layers, whereas sills are parallel.
A rock may respond to stress in one of three basic ways. Match the image with the type of response shown.
Displacement matches Choice, Image A Image A Rotation matches Choice, Image B Image B Strain matches Choice, Image C Image C
Rocks respond to stress in different ways. Match the types of stress response to their explanations.
Displacement matches Choice, Rock is moved from one place to another; faulting may occur. Rock is moved from one place to another; faulting may occur. Rotation matches Choice, Rock is folded, lifted, or spun horizontally. Rock is folded, lifted, or spun horizontally. Strain matches Choice, Change of shape occurs without layers breaking or tilting. Change of shape occurs without layers breaking or tilting. Unchanged matches Choice, There is a small amount of stress; volume of rock is the same. There is a small amount of stress; volume of rock is the same.
Which of the following are true of earthquakes related to continental collisions?
Earthquakes are widely distributed along the collision zone. They may occur in large thrust faults created near the plate boundary. A megathrust between the two plates creates large earthquakes. They may occur in either continental plate.
What is differential erosion?
Erosion that varies due to rock type
Match the expression of a fault with its description.
Fault scarp matches Choice, A step in the landscape created when fault movement offsets the surface A step in the landscape created when fault movement offsets the surface Termination of layers matches Choice, Motion along a fault causing layers of rock to be abruptly truncated Motion along a fault causing layers of rock to be abruptly truncated Linear scratch marks matches Choice, Created when fault surfaces slip and may be used to infer direction of fault motion Created when fault surfaces slip and may be used to infer direction of fault motion
What happened in and along the sea during the Great Alaskan Earthquake of 1964?
Faulting and uplift of the seafloor occurred, creating a large tsunami in the Pacific Ocean. Some areas subsided and were flooded by seawater. Some land that was below the sea was uplifted above sea level.
Compare a syncline to an anticline by putting the labels in the correct categories.
Figure A matches Choice, Anticline Anticline Figure B matches Choice, Syncline Syncline
______ per unit area is ______.
Force; stress
In which ways may a fault be recognized in a landscape?
Offset beds Scratched and shattered rocks Fault scarp
Which of the following accurately describe shield volcanoes?
Have vents and fissures from which lava escapes Have a broad and gently sloping form Composed of a succession of basaltic lava flows
If compressive stress is applied in the directions indicated by the arrows (consider that the arrows directly oppose one another), what will likely happen to the rock layers?
If rocks deform in a ductile manner, they will fold in a direction perpendicular to the stresses.
How might humans cause earthquakes and/or seismic waves?
Injecting wastewater underground may induce earthquakes. Explosions may compress Earth's surface. Constructing reservoirs may cause flexing and faulting of the crust.
How does folding create local mountains?
Layers are warped within Earth and then uplifted.
What are the different ways in which volcanic activity can create earthquakes?
Moving magma pushing rocks Landslides created by weakened rocks Volcanic gases escaping in an explosion Faulting associated with caldera collapse
What types of volcanic activity at a composite volcano create a local mountain?
Mudflows Ash layers Lava flows
Match the type of fault with its description.
Normal matches Choice, Block above the fault moves down relative to block below the fault. Block above the fault moves down relative to block below the fault. Reverse matches Choice, Block above the fault moves up relative to block below the fault. Block above the fault moves up relative to block below the fault. Strike-slip matches Choice, Fault motion is horizontal. Fault motion is horizontal. Thrust matches Choice, This is a low-angle reverse fault. This is a low-angle reverse fault.
Direct damage and secondary effects of earthquakes are listed below. Choose those that are secondary effects.
Ruptured natural gas lines cause explosions and fires. Flooding of dry land occurs as seawater inundates subsided areas.
What is the relationship between the viscosity of a magma and the ease with which its gases can escape?
The higher the viscosity, the harder it is for gas to escape.
Based on these images, which are true of the subduction zone and indicated earthquakes? (Yellow dots = shallow-depth earthquakes; green dots = intermediate; red dots = deep.)
The subducted plate is generally inclined from west to east, with the deepest portion of the slab to the east. Shallow earthquakes are closer to the trench, whereas deep ones are farther away.
What defines an earthquake?
The sudden release of energy stored in rocks
Which of the following is not true of calderas?
They are cone-shaped.
Choose all of the characteristics of volcanic domes.
They are domed-shaped. They vary in size from hundreds of meters to a few kilometers.
In which direction is subduction occurring at the location indicated on the map?
To the northwest
Erupting basaltic lava may first form a cinder cone when it is accompanied by gas, but once the gas is used up, the eruption becomes ______.
a lava flow
The most abundant igneous rock on Earth's surface is
basalt
A single volcano may produce ______.
both explosive and nonexplosive eruptions
Match the type of fault with the way in which it can form a local basin.
downdropping horizontal weight
Cinder cones are primarily made of ______.
ejected fragments of basaltic lava
When tilted and folded layers erode, ______.
erosion of soft and hard layers can carve a dip slope differential erosion of dipping layers can create a hogback
A magma that has a low viscosity will allow to escape relatively easily, resulting in nonexplosive eruptions. (The answer is just one word.)
gas, gases, or volatiles
We find basalt on Earth's surface ______.
in flow deposits on every continent as the upper part of ocean crust
Surface features formed from igneous rocks can be irregular in shape, like large batholiths, or can be pipelike, as with volcanic necks.
intrusive
different types of form due to tectonic stresses, the cooling and contraction of igneous rocks, and the uplift and unloading of buried rocks.
joints
subdivision
liquefaction
Regional mountain chains are associated with wide-scale tectonic processes that create thick crust, whereas ______ mountains are built in various ways on top of the crust.
local
Flood-basalt eruptions are fed by ______.
long fissures/dikes
A fold with a relatively simple single steplike bend is called a(n) ______.
monocline
What is the name of the simple fold shown here?
monocline
Earthquakes and/or seismic waves may be caused by ______.
nuclear explosions landslides movement along faults volcanic eruptions and magma movement
Moving magma associated with volcanic activity generates earthquakes by ______.
putting stress on nearby rocks
This thrust fault is a type of fault
reverse
The large magnitude of the 1964 Alaskan earthquake produced severe that caused landslides, building collapse, avalanches, and liquefaction.
shaking
True or false: Folding can create local mountains by processes that occur either at the surface or within Earth.
true
The breaking of underground ______ lines during the shaking of an earthquake commonly lead to and exacerbate fires.
water natural gas