CH 4 - Study Guide

Describe the eruption of Mount St. Helens by placing the labels next to the correct image depicting the order of events from top to bottom.

A bulge grows on the north side of the volcano. An earthquake loosens the bulge, causing an enormous landslide. The volcano erupts in a lateral blast. Gases propel ash vertically into the atmosphere.

_____ describes the surface of a basalt flow with a jagged, rubble surface.

Aa

Most of the better-known composite volcanoes on Earth are ____.

All the choices are correct, except in the mid-ocean ridge system.

_________ crystallizes from an intermediate composition lava.

Andesite

Shield volcanoes have ___ bases and ___ inclined slopes.

Broad; Gently

What type of volcano is short-lived, relatively small, and is commonly on the flanks of other volcanoes?

Cinder cone

The bottom left figure shows a ____________ (type of volcano) that forms from ____________ (type of eruption).

Composite Volcano; eruption of viscous, felsic lava

This figure shows the distribution of volcanoes along a ________- boundary. These volcanoes are typically _________ in structure and ________ in composition.

Convergent; Composite; Andesitic

Composite volcanoes are also called cinder cone volcanoes.

False

Earth is the only major body in the solar system on which there are active volcanoes.

False

Kilauea on the island of Hawaii has been erupting continuously since 1983.

False

Major volcanic peaks of the Cascade Mountains, like Mt. Rainier, Mt. Shasta, Mt. Hood, and Mt. St. Helens, have been active volcanoes for 30 to 40 million years.

False

Measurements indicate that the worldwide average temperature dropped about a half degree Celsius for a couple of years after the eruption of Mt. Pinatubo in 1991.

False

Most of the gas released by volcanic eruptions is carbon dioxide.

False

Silicic lavas, which are relatively high in silica, tend to be more fluid than mafic magmas.

False

Tsunamis account for most fatalities in volcanic eruptions.

False

Volcanic eruptions have no effect on climate.

False

Volcanic rocks, and the magma from which they formed, have a silica content that ranges from 45% to 75% by volume.

False

In what country was the largest fissure eruption of flood basalts documented by humans?

Iceland

A typical example of a shield volcano is

Kilauea in Hawaii

The term ___ is used for molten rock on the Earth's surface.

Lava

_____ are tunnel-like caves within a lava flow.

Lava Tubes

Drag the proper label of the eruption type to the correct photograph.

Left: Effusive, Explosive, Effusive Right: Effusive, Effusive, Explosive

An example of a composite volcano is

Mount Rainier Fujiyama Mount Vesuvius all of the preceding

The eruption of ______ is related to the fact that the North American plate is overriding a portion of the Pacific Ocean floor.

Mount St. Helens

The last volcano to erupt in the continental 48 states was __.

Mount St. Helens

One gas typically not released during a volcanic eruption is

Oxygen

_____ describes the surface of a basalt flow with a smooth ropy surface.

Pahoehoe

The Roman city of _____ was destroyed by the eruption of Vesuvius in 79 AD.

Pompeii

A(n) _______ is a mix of gas and dust emitted by a volcano that is so dense that it hugs the ground.

Pyroclastic Flow

List the volcanic hazards in order of explosiveness.

Pyroclastic flow, Flood Basalt, Aa Lava flow, Pahoehoe lava flow

The top left figure shows a ____________ (type of volcano) that forms from ____________ (type of eruption).

Scoria cinder cone; Pyroclastic material

The islands of the Hawaiian chain are an excellent example of a series of __.

Shield Volcanoes

Drag the proper label of the volcano type to the correct photograph.

Shield; Composite; Cinder Cone; Composite; Lava dome

These photographs show different types of eruptions. Drag the name of the eruption type to the correct photograph.

TL: Lava Flow. TR: Lava Fountain BL: Lava Dome BR: Eruption Column

What do we call the numerous volcanoes that circle the edge of the Pacific Ocean?

The Ring of Fire

What do Hawaii and Yellowstone have in common volcanically?

They are the result of a mantle plume.

What do Yellowstone, Crater Lake, and Long Valley, California, have in common volcanically?

They have had caldera eruptions.

Columnar jointing is a characteristic of basalt lava.

True

Pahoehoe lava flow is characterized by a ropy or billowy surface.

True

Pillow structures, pillow-shaped rounded masses, form where lava is extruded under water.

True

The islands of Hawaii are essentially a series of shield volcanoes built upward from the ocean floor over millions of years.

True

The original volcano Mount Mazama erupted to form Crater Lake, Oregon.

True

Tuff is a rock composed of fine-grained pyroclastic particles.

True

Volcanic domes are steep-sided domes or spine-shaped masses of volcanic rock formed from viscous lava that solidifies in or immediately above a volcano's vent.

True

Weathered volcanic ash and lava produce excellent fertile soils.

True

________ is a rock composed of fine-grained pyroclastic particles.

Tuff

Radar images of which planet show a surface that is young and still volcanically active?

Venus

How do scientists indicate the power of a volcanic eruption?

Volcanic Explosivity Index

The bottom right figure shows a ____________ (type of volcano) that forms from ____________ (type of eruption).

Volcanic dome; eruption of lava and ash

_________ is a hill or mountain formed by the extrusion of lava or ejection of rock fragments from a vent.

Volcano

Determine the type and plate setting of each specific volcano by placing the labels in the correct location.

Yellowstone, Caldera, Continental Hot Spot Mt. Rainer, Composite, Subduction Killauea, Shield, Oceanic Hot Spot

The most common mafic volcanic rock is __.

basalt

The largest pyroclasts are __.

bombs/blocks

Volcanic activity in Hawaii is beneficial in all the following ways except ______.

burying existing residential land

A _________ is a volcanic depression much larger than the original crater, formed when the volcano collapses into a vacated magma chamber.

caldera

A ______ is a volcano constructed of pyroclastic fragments ejected from a central vent.

cinder cone

Individual layers of basalt lava may be divided into vertical columns called ______.

columnar basalt

A _____ volcano is composed of alternating layers of pyroclastic fragments and solidified lava flows.

composite

Which volcano is not usually made of basalt?

composite cone

New oceanic crust is formed at ____________ plate boundaries where the volcanic activity is usually ____________ viscosity.

divergent; low

The Columbia Plateau in Washington is a good example of a ______, a massive volcanic outpouring of mafic, runny lava.

flood basalt

For the volcanic eruption in this photograph, complete the three missing parts of the sentence using the viscosity, composition, and resulting rock type.

high-viscosity; felsic or intermediate; pumice

For the volcanic eruption in this photograph, complete the three missing parts of the sentence using the viscosity, composition, and resulting rock type.

high-viscosity; felsic or intermediate; rhyolite or andesite

Mount St. Helens

last erupted violently in 1980 is part of the Cascade Range had a revival of dome growth in 2004 All choices are correct

For the volcanic eruption in this photograph, complete the two missing parts of the sentence using the type of volcanic feature and type of magma.

lava flow; eruption of low-viscosity, mafic lava

For the volcanic eruption in this photograph, complete the three missing parts of the sentence using the viscosity, composition, and resulting rock type.

low viscosity; mafic; vesicular basalt

Eruptions of shield volcanoes fed by mafic magma tend __.

not to be explosive or particularly dangerous

The lava that flows out on the sea floor near divergent plate boundaries takes the form of

pillow basalt

Several times in Earth's history, outpourings of magma covered many thousands of square kilometers in multiple flows called __.

plateau basalts

Which is not one of the aspects of reducing volcanic hazards?

prevention

A _____ is a mixture of gas and pyroclastic debris that is so dense that it hugs the ground as it flows rapidly into low areas.

pyroclastic flow

A _________, a mixture of gas and volcanic debris, may blast out laterally under a viscous plug capping a volcano.

pyroclastic flow

In 1902 the port city of St. Pierre on the island of Martinique was destroyed by a ___.

pyroclastic flow

Occasionally, a volcano will spew large amounts of fine volcanic dust into the high atmosphere. This dust can have the effect of __.

reducing the sunlight that reaches Earth's surface, suppressing photosynthetic processes. reducing Earth's surface temperature damaging aircraft that fly through the dust causing unusual weather All of the answers are correct

The most abundant silicic volcanic rock is __.

rhyolite

The top right figure shows a ____________ (type of volcano) that forms from ____________ (type of eruption).

shield volcano; eruption of basaltic lava flows

The largest volcano in the solar system is a ______ volcano on ______.

shield; Mars

Eplosive eruption tend to have higher _____ content in the source magma

silica

What are the three factors that influence viscosity of a lava?

silica content, temperature, dissolved gases

Because _____ magmas are the most viscous they are associated with the most violent eruptions.

silica-rich

Crater Lake is a volcanic feature of _____.

the Cascade Mountains

Whether volcanic eruptions are very explosive or relatively quiet is largely determined by

the amount of gas in the lava or magma the ease or difficulty with which the gas escapes to the atmosphere the viscosity of a lava All of the choices are correct.

Over 34,000 people died as a result of the ______ generated by the eruption of Krakatoa in 1883.

tsunami

The more _____ the lava, and the greater the amount of gas trying to escape, the more violent the eruption.

viscous

Volcanic domes are steep-sided, spine-shaped masses of volcanic rock formed from _______ magma.

viscous

Volcanic eruptions can affect the climate because

volcanic dust and gas can reduce the amount of solar radiation that penetrates the atmosphere

A lahar is a(n) ______.

volcanic mudflow