MULTIPLE CHOICE
 

1. 1 meter = ___ km?

a. 1
b. 10
c. 0.1
d. 100
e. 0.001
 

2. 1000 cm = ___ meters?

a. 1
b. 10
c. 100
d. 0.1
e. 0.01
 

3. A caldera volcano:

a. is the result of the largest and most explosive volcanic eruption
b. causes the ground to subside
c. is built from particles and  blobs of congealed lava ejected from a single vent
d. b and c
e. a and b
 
feedback
The largest and most explosive volcanic eruptions eject tens to hundreds of cubic kilometers of magma onto the Earth's surface. When such a large volume of magma is removed from beneath a volcano, the ground subsides or collapses into the emptied space, to form a huge depression called a caldera

4. Lava domes:

a. are the simplest form of volcano
b. range in composition from dacite to rhylite
c. are masses of cooled lava
d. a and b
e. b and c
 
feedback
Most domes are composed of silica-rich lavas that have a lower gas content than do the lavas erupted earlier in the same eruptive sequence; nevertheless, some dome lavas still contain enough gas to cause explosions within a dome as it is being formed.  Domes ranging in composition from dacite to rhyolite have erupted on numerous occasions
 

5. Basltic lava in shield-volcanic eruptions:

a. can pour out of long fissures
b. can pour out of central vents
c. create lava domes
d. are usually very thin
e. all of the above
 
feedback
In some shield-volcano eruptions, basaltic lava pours out quietly from long fissures instead of central vents and floods the surrounding countryside with lava flow upon lava flow, forming broad plateaus
 

6. The origin of Yellowstone is:

a. stratovolcano
b. caldera
c. hotspot
d. ring of fire
e. volcanic dome

feedback
Scientists have traced Yellowstone's origin to a hot spot in the mantle, one of a few dozen such hot spots on Earth. Buoyant material from a hot spot rises through the upper mantle, bringing heat from the Earth's interior closer to the surface. The Yellowstone hot spot impinges on the base of the North American plate, one of several rigid plates that make up the Earth's crust. These plates move a few inches per year with respect to the stationary hot spots and each other, sometimes causing great earthquakes as the plates collide, grind past one another, or split apart
 
 

7. Volcanic cones consisting of lava rock interlayered with pyroclastic deposits is a:

a. cinder cone
b. caldera
c. volcanic dome
d. lava dome
e. composite cone

feedback
Mount St. Helens, like most other Cascade volcanoes, is a great cone of rubble consisting of lava rock interlayered with pyroclastic and other deposits. Volcanic cones of this internal structure are called composite cones or stratovolcanoes.
 

8. The word "phreatic" means:

a. explosion
b. steam-blast
c. nuclear explosion
d. pyroclastic blast
e. lateral blast

feedback
small phreatic (steam-blast) explosions

9. Endogenous means:

a. something that is native to an area
b. a person who studies volcanoes
c. growth from within
d. a person who studies earthquakes
e. growth from the ground up

feedback
endogenous growth (growing from within)

10. The Hawaiian Islands:

a. are intra-plate volcanoes
b. are inter-plate volcanoes
c. are over a hot spot
d. a and b
e. b and c

feedback
The Hawaiian Islands provide perhaps the best example of an "intra-plate" volcanic chain, developed by the northwest-moving Pacific Plate passing over an inferred "hot spot" that initiates the magma-generation and volcano-formation process.
 

11. The Jaun de Fuca Ridge is:

a. a submarine mountain chain in the Pacific ocean
b. a valley where older volcanoes are found in the Pacific ocean
c. a submarine mountain chain in the Atlantic ocean
d. the boundary between the Pacific and North American plates
e. a and b

feedback
The boundary between the Pacific and Juan de Fuca Plates is marked by a broad submarine mountain chain about 500 kilometers long, known as the Juan de Fuca Ridge. Young volcanoes, lava flows, and hot springs were discovered in a broad valley less than 8 kilometers wide along the crest of the ridge in the 1970's. The ocean floor is spreading apart and forming new ocean crust along this valley or "rift" as hot magma from the Earth's interior is injected into the ridge and erupted at its top.
 

12. The Cascades were formed by:

a. the collision of an oceanic and continental plate
b. the collision of the Jaun de Fuca and North American plates
c. intra-plate volcanoes
d. a and b
e. a and c

feedback
However, some active volcanoes are not associated with plate boundaries, and many of these so-called "intra-plate" volcanoes form roughly linear chains in the interior of some oceanic plates. The Hawaiian Islands provide perhaps the best example of an "intra-plate" volcanic chain. In the Pacific Northwest, the Juan de Fuca Plate plunges beneath the North American Plate, locally melting at depth; the magma rises to feed and form the Cascade volcanoes.

13. Divergent boundaries are found

a. at the mid-Atlantic ridge
b. in the Pacific ocean
c. in the rift valley
d. in the San Andreas fault
e. a, b and c

feedback
Divergent or spreading -- adjacent plates pull apart, such as at the Mid-Atlantic Ridge, which separates the North and South American Plates from the Eurasian and African Plates.
 

14. Earthquakes

a. occur along the other, brittle portions of tectonic plates
b. occur where temperatures in the rock are high
c. occur where temperatures in the rock are low
d. a and b
e. a and c

feedback
Earthquakes occur only in the outer, brittle portions of these plates, where temperatures in the rock are relatively low
 

15. Composite volcanoes

a. have a central vent
b. have a cluster of vents
c. have dikes that form ribs to strengthen the volcano
d. lava flow through breakers in the crater walls or fissures
e. a, b, c and d

feedback
Most composite volcanoes have a crater at the summit which contains a central vent or a clustered group of vents. Lavas either flow through breaks in the crater wall or issue from fissures on the flanks of the cone. Lava, solidified within the fissures, forms dikes that act as ribs which greatly strengthen the cone.
 

16. Shield volcanoes

a. erupt explosively
b. erupt non-explosively
c. are the same as composite volcanoes
d. are the same as a stratovolcano
e. are found in the Cascades

feedback
Composite volcanoes tend to erupt explosively and pose considerable danger to nearby life and property. In contrast, the gently sloping shield volcanoes, such as those in Hawaii, typically erupt nonexplosively, producing fluid lavas that can flow great distances from the active vents.
 

17. Volcanic domes

a. can result in high-velocity ash flows
b. are found on Mount Pelee
c. are the same as lava domes
d. commonly occur within the craters of composite volcanoes
e. all of the above

feedback
An extremely destructive eruption accompanied the growth of a dome at Mount Pelee in 1902. The coastal town of St. Pierre, about 4 miles downslope to the south, was demolished and nearly 30,000 inhabitants were killed by an incandescent, high-velocity ash flow and associated hot gases and volcanic dust.
 

18. Flood basalts

a. are theoliitic basalt magma flows
b. are olivine basalt magma flows
c. are cast composite accumulation of lava
d. can be sub-horizontal
e. all of the above

feedback
A term applied to those basaltic lavas that occur as vast composite accumulations of horizontal or subhorizontal flows and which, erupted in rapid succession over great areas, have at times flooded sectors of the earth's surface on a regional scale. They are generally believed to be the product of fissure eruptions and tend to conform to either one of two standard compositions, distinguished as the tholeiitic and olivine basalt magma types respectively
 

19. Deep sub-marine volcanoes

a. usually disturb the ocean surface when they erupt
b. produce lots of blasting steam
c. cause rocks to be thrown great distances above the water
d. are found on Hawaii
e. none of the above

feedback
 Submarine volcanoes and volcanic vents are common features on certain zones of the ocean floor. Some are active at the present time and, in shallow water, disclose their presence by blasting steam and rock-debris high above the surface of the sea. Many others lie at such great depths that the tremendous weight of the water above them results in high, confining pressure and prevents the formation and explosive release of steam and gases. Even very large, deepwater eruptions may not disturb the ocean surface
 

20. The Yellowstone hotspot

a. is formed from magma near the surface of a plate
b. shows the north-westward movement of the North American plate
c. is the largest hotspot in the world
d. is formed from rhylite magma explosions
e. is the most recent location of a hot spot that has affected land in Washington, Oregon, Idaho, California, and Nevada

feedback
The Yellowstone hot spot has interacted with the North American plate for perhaps as long as 17 million years, causing widespread outpourings of basalt that bury about 200,000 square miles in Washington, Oregon, California, Nevada, and Idaho under stacks of lava flows half a mile or more thick. Some of the basaltic melt, or magma, produced by the hot spot accumulates near the base of the plate, where its heat melts rocks from the Earth's lower crust. These melts, in turn, rise closer to the surface to form large reservoirs of potentially explosive rhyolite magma. Catastrophic eruptions have partly emptied some of these reservoirs, causing their roofs to collapse. The resulting craters, some of which are more than 30 miles (50 kilometers) across, are known as volcanic calderas. Because the plate was moving an inch or so per year southwestward over the hot spot for millions of years as the calderas formed, groups of calderas are strung out like beads on a string across parts of Idaho and Wyoming

TRUE/FALSE

1. More than half of the worlds active volcanoes are below sea level
 
 False.  More than half of the world's active volcanoes above sea level encircle the Pacific Ocean
 
 
2. A continental plate subducts beneath an oceanic plate
 
 False.  Where plates converge, one tips down and slides beneath the other. Generally, an oceanic plate slides ("subducts") beneath a continental plate (for example, along the west coast of South America) or another oceanic plate (for example, the east side of the Philippine Sea plate).
 
 
3. Shield volcanoes are built almost entirely on lava plateaus

False.   Shield volcanoes ... are built almost entirely of fluid lava flows.
 

4.  Cinder cone volcanoes rarely rise more than a thousand feet

True.  Most cinder cones have a bowl-shaped crater at the summit and rarely rise more than a thousand feet or so above their surroundings
 

5.  Yellowstone has erupted within the last 600,000 years

True.  Cataclysmic eruptions 2.0, 1.3, and 0.6 million years ago ejected huge volumes of rhyolite magma; each eruption formed a caldera and extensive layers of thick pyroclastic-flow deposits