Geology Chapter 11 Quiz

Which of the numbered features is a pyroclastic flow?

4

What event triggered the main eruption of Mount St. Helens in May 1980?

A landslide removed rocks and released pressure on the magma.

What is common in most calderas?

A large circular depression with steep walls Thick sequences of volcanic ash Rounded mountains that are volcanic domes

Which of the following are differences between an eruption column and pyroclastic flow?

A pyroclastic flow forms when the gas flux cannot support the column.

Which of the following is not a major controlling factor on volcanic eruption style?

Age of volcano

Shield volcanoes, like Mauna Loa, have what kind of slopes?

Broad, gentle

Which of the following is not a hazard typically associated with cinder cones?

Bulldozing of houses from their foundations

Which of the following is not a typical eruption style during the growth of a composite volcano?

Caldera collapse

Huge circular depressions from which volcanoes erupt are called

Calderas

Eruptions on the island of Santorini in Greece resulted in

Collapse of a huge caldera that caused part of an island to disappear beneath the sea. A huge ash column and pyroclastic flows. Destructive waves that traveled across the sea.

Which of the following is a location in which flood basalts erupted?

Columbia Plateau

What type of material likely composes this volcano? (Game McGlmsey/Alaska Volcano Observatory)

Felsic to intermediate lava flows Pyroclastic flows Volcanic mudflows and landslides

What are the characteristics of actively erupting volcanoes?

Glowing orange lava flowing downhill. Fragments of molten rock blasting into the air. Billowing clouds of ash rising into the air.

What tectonic setting is interpreted to be the cause of volcanism at Yellowstone?

Movement of North America over a mantle plume

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

Pacific Ring of Fire.

Which of the following volcanoes is generally the largest?

Shield Volcano

Comparing these two photographs, which eruption has lower viscosity magma?

The fluid cascade of lava

Which of the following rock types is not characteristic of volcanic domes?

Vesicular basalt with very large holes from dangerous gas

Which of the following would be evidence that a volcano has not been active for a long period of time?

Well-developed soils on volcanic rocks

A volcanic eruption occurring beneath an ice sheet is likely to cause

a hazardous flood.

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

andesite

Composite volcanoes are so called because they

are composed of lava flows, pyroclastic material, and mudflows.

Shield volcanoes are composed primarily of

basalt lava flows.

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

be explosive.

A single volcano may produce

both explosive and nonexplosive eruptions. Correct

Which of the following types of eruptions is among the most deadly of natural disasters?

caldera-forming

A volcanic neck can form by

erosion of the volcano, leaving behind the solidified conduit inside the volcano. erosion of overlying rock layers exposing the conduit below the volcano.

Ash layers from the three most recent caldera-forming eruptions at Yellowstone (2.1, 1.3, and 0.64 million years ago) stretch

from Canada to Mexico.

Flood basalt eruptions are fed by

long fissures/dikes.

Earthquakes at Mount St. Helens prior to the major eruption in 1980 were caused by

magma rising in the volcano.

Compared to a younger cinder cone, an older cinder cone would have

more soil and plants.

The igneous feature shown in this figure is a

sill

When lava flows reach the ocean, they

solidify and add land to an island.

Shield volcanoes have low slopes primarily because

the low viscosity of basaltic magma allows it to flow downhill for long distances.

The higher the gas pressure builds in a magma,

the more explosive the eruption.