Quiz 4: Volcanism and Extrusive Rocks

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

Weathered volcanic ash and lava produce excellent fertile soils.

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.

Tsunamis account for most fatalities in volcanic eruptions.

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

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

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

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

Basalt is a variety of gabbro.

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

Basalt is the most common mafic rock.

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

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.

Columnar jointing is a characteristic of basalt lava.

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

Composite volcanoes are also called cinder cone volcanoes.

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

Rhyolite is a fine-grained extrusive rock composed of feldspar with some quartz.

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

Volcanic eruptions have no effect on climate.

The last volcano to erupt in the continental 48 states was __. A) Mount Garibaldi B) Mount Rainer C) Mount Mazama D) Mount St. Helens E) Mount Fuji

The term ___ is used for molten rock on the Earth's surface. A) lava B) tuff C) magma D) tephra E) cinder

A(n) _______ is a mix of gas and dust emitted by a volcano that is so dense that it hugs the ground. A) pyroclastic flow B) pahoehoe flow C) obsidian D) lava flow E) tuff flow

Condensation of the water vapor by degassing magma during the time following Earth's formation produced the ____. A) atmosphere B) geosphere C) hydrosphere D) magneosphere E) biosphere

The islands of the Hawaiian chain are an excellent example of a series of __. A) cinder cones B) composite volcanoes C) spatter cones D) shield volcanoes E) strata volcanoes

_____ are tunnel-like caves within a lava flow. A) Pores B) Vesicles C) Lava tubes D) Lava pipes E) Calderas

Shield volcanoes have ___ bases and ___ inclined slopes. A) broad; steeply B) broad; gently C) narrow; steeply D) narrow; gently

Occasionally, a volcano will spew large amounts of fine volcanic dust into the high atmosphere. This dust can have the effect of __. A) reducing the sunlight that reaches Earth's surface, suppressing photosynthetic processes B) reducing Earth's surface temperature C) damaging aircraft that fly through the dust D) causing unusual weather E) All of the answers are correct.

What are the three factors that influence viscosity of a lava? A) depth of magma, temperature, ease of gas escaping to atmosphere B) amount of gas, rhyolite, and vesicules in the magma C) origin of the magma, plate tectonic setting, condensation D) plate tectonic setting, thickness of the geosphere, amount of gas in the magma E) silica content, temperature, dissolved gases

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. A) silica flow B) lava flow C) pyroclastic flow D) change in viscosity E) pahoehoe lava flow

The Roman city of _____ was destroyed by the eruption of Vesuvius in 79 AD. A) Rome B) Pompeii C) St. Pierre D) Naples E) Florence

The more _____ the lava, and the greater the amount of gas trying to escape, the more violent the eruption. A) viscous B) fluid C) hot D) older E) oxygenated

How do scientists indicate the power of a volcanic eruption? A) Viscosity charts B) Volcanic Explosivity Index C) Hawaiian volcanic index D) Dissolved gas charts E) Volcanic Eruptive Indicator

Because _____ magmas are the most viscous they are associated with the most violent eruptions. A) silica-rich B) iron-rich C) carbon dioxide-rich D) water-rich E) older

The most abundant silicic volcanic rock is __. A) basalt B) andesite C) rhyolite D) tuff E) obsidian

The most common mafic volcanic rock is __. A) basalt B) andesite C) rhyolite D) tuff E) obsidian

A _____ volcano is composed of alternating layers of pyroclastic fragments and solidified lava flows. A) shield B) composite C) cinder cone D) caldera E) plateau

_________ crystallizes from an intermediate composition lava. A) Andesite B) Basalt C) Gabbro D) Composite E) Rhyolite

Eruptions of shield volcanoes fed by mafic magma tend __. A) to be violent and potentially dangerous events B) to be explosive but short-lived C) not to be explosive or particularly dangerous D) to result in the expulsion of vast amounts of tephra E) to cover the surrounding landscape in ash

Volcanic domes are steep-sided, spine-shaped masses of volcanic rock formed from _______ magma. A) viscous B) fluid C) mafic D) unusually hot E) low-viscosity

_____ refers to a rock's appearance with respect to the size, shape, and arrangement of its grains or other constituents. A) Crystallinity B) Texture C) Extrusiveness D) Magma E) Viscosity

_________ is a hill or mountain formed by the extrusion of lava or ejection of rock fragments from a vent. A) Caldera B) Flank eruption C) Pillow lava D) Volcano E) Cinder cone

The eruption of ______ is related to the fact that the North American plate is overriding a portion of the Pacific Ocean floor. A) Fuji B) Tamboro C) Mount St. Helens D) Mount Pelee E) Mauna Loa

In 1902 the port city of St. Pierre on the island of Martinique was destroyed by a ___. A) tsunami B) lava flow C) mud flow D) poison gas cloud E) pyroclastic flow

Over 34,000 people died as a result of the ______ generated by the eruption of Krakatoa in 1883. A) tidal wave B) suzuki C) roller D) tsunami E) whitecap

Crater Lake is a volcanic feature of _____. A) the Cascade Mountains B) Hawaii C) the Aleutian Islands D) the Ouachita Mountains E) Baja California

A _________ is a volcanic depression much larger than the original crater, formed when the volcano collapses into a vacated magma chamber. A) vent B) caldera C) basin D) ring dike E) crater

A ________ igneous rock is one in which larger crystals are enclosed in a groundmass of much finer-grained material. A) aphanitic B) phaneritic C) polyphonic D) porphyritic E) mylonitic

________ is a frothy volcanic glass with so much void space that it can actually float. A) Obsidian B) Sponge rock C) Pumice D) Lava E) A floater

The largest pyroclasts are __. A) ash and dust B) bombs/blocks C) cinders D) lapillis E) sand

_____ describes the surface of a basalt flow with a smooth ropy surface. A) Pahoehoe B) Aa C) Haleakela D) Poy E) Pele's hair

_____ describes the surface of a basalt flow with a jagged, rubble surface. A) Pahoehoe B) Aa C) Haleakela D) Poy E) Pele's hair

Individual layers of basalt lava may be divided into vertical columns called ______. A) pahoehoe B) columnar basalt C) pillow structure D) collapse structure E) tuff

A ______ is a volcano constructed of pyroclastic fragments ejected from a central vent. A) shield volcano B) caldera C) stratovolcano D) dome E) cinder cone

________ is a rock composed of fine-grained pyroclastic particles. A) Tuff B) Pumice C) Scoria D) Rhyolite E) Obsidian

________ are cavities in extrusive rocks resulting from gas bubbles in the lava. A) Phenocrysts B) Pleochroic C) Vesicles D) Vascular E) Holy

Several times in Earth's history, outpourings of magma covered many thousands of square kilometers in multiple flows called __. A) pillow basalts B) plateau basalts C) rift basalts D) sheet basalts E) regional basalts

A _________, a mixture of gas and volcanic debris, may blast out laterally under a viscous plug capping a volcano. A) pyroclastic flow B) mud flow C) debris flow D) lava flow E) lahar

Radar images of which planet show a surface that is young and still volcanically active? A) Mercury B) Venus C) Mars D) Neptune E) Saturn

Most of the better known composite volcanoes on Earth are __. A) in the mid-ocean ridge system B) in the circum-Pacific belt C) in the Mediterranean belt D) All of the choices are correct. E) All of the choices are correct, except in the Mediterranean belt.