ch 5 volcanoes

part b: which of the following pieces of evidence for a past volcanic eruption are present at yellowstone national park?

a caldera rim; pyroclastic material; lava flows

part h: what is a mantle plume?

a circular column of magma that rises from deep within earth

distinguish among a conduit, a vent, and a crater.

a conduit is the circular path through which magma ascends to the vent, which is the surface opening of the conduit. a crater is a funnel-shaped depression around the vent.

which of the following choices best explains the difference between a crater and a caldera?

a crater is a small, funnel-shaped depression; a caldera is a large depression that has a diameter of over 1 km

part b: what is the difference between a dike and a sill?

a dike intrudes across sedimentary layers, and a sill intrudes between sedimentary layers.

how does the composition of a typical lava dome differ from that of a typical fissure eruption?

a lava dome's flow is silica-rich and has a high viscosity, whereas a fissure eruption is basaltic and has a low viscosity.

part a: which of the following objects has a size similar to that of lapilli?

a marble (15 mm)

part c: which of the following often forms after continental rifting?

a new ocean basin

are volcanoes fed by highly viscous magma a greater threat to life and property than volcanoes supplied with very fluid magma?

a volcano fed by highly viscous magma is a greater threat to life and property because it is more explosive and, thus, is more difficult or impossible to predict.

how does the viscosity of the magma fed to volcanoes affect nearby life and property?

a volcano that expels highly viscous magma is a greater threat to life and property because it is more explosive and thus is more difficult or impossible to predict.

which of the following can be a product of a composite volcano eruption? choose all that apply.

all of the above (volcanic bombs; gases; andesitic lava; cinders; ash)

part c: yellowstone is best described as which of the following?

an active volcano that has erupted in the last 1 million years

which of the following would decrease the viscosity of magma?

an increase in temperature

why would flying a commercial jet through a cloud of volcanic ash be dangerous?

ash impairs visibility, clogs engines, and abrades engine parts.

what kind(s) of lava generate a cinder cone?

basalt

part e: what is a magma chamber called after the conduit has solidified and been exposed by erosion?

batholith

part f: how are island arc and continental arc magmas similar?

both are formed near subduction zones.

what three factors do volcanologists monitor in order to determine whether magma is migrating toward the earth's surface?

changes in the patterns of earthquakes caused by the movement of magma, inflation of the volcano, and the gases released from the volcano

when contrasting lava from composite volcanoes to lava from shield volcanoes,

composite volcanoes most often produce silica-rich lavas with high viscosities, whereas shield volcanoes produce basaltic lavas with low viscosities.

all types of volcanic cones share which feature?

conduit

part d: which of the following is the volcanic feature in which magma rises through before it is released at the surface?

conduit

part e: how are continental rift magmas and continental arc magmas different?

continental arc magmas are more viscous than continental rift magmas.

part a: which of the following are common tectonic settings associated with volcanic activity? choose all that apply.

continental arcs; island arcs; continental rifts; mantle plumes

part d: which of the following was a stage in the formation of yellowstone caldera?

crust bows upward above a magma chamber.

which type of plate boundary generates the greatest quantity of magma?

divergent

t/f: mt st helens was mostly effusive lava flows, while kilauea is mostly explosive volcanism

false

________ are small vents that emit volcanic gases.

fumaroles

the volcanoes in the ring of fire are generally described as

having violent eruptions, as most of these volcanoes are composite cones which eject andesitic lava.

part i: which of the following is an example of modern-day mantle plume volcanism?

hawaiian islands

a lava tube forms because the lava in the ________ part of the flow remains fluid, while the exposed surface ________ and hardens

interior; cools off

part c: which of hawaii's five volcanoes are still considered to be active? choose the two that apply.

kilauea; mauna loa

part c: which of the following volcanic materials flows out of a volcanic vent?

lava

what kind of viscosity would flood basalts have?

low viscosity

part a: what lies underneath volcanic features at Earth's surface?

magma chambers and volcanic conduits

part a: which of the following scenarios best describes how the hawaiian islands formed in the pacific ocean?

magma generated from a hot spot burned through the overlying plate to create volcanoes.

part b: which materials in hawaii's lava help to keep it fluid for longer at the surface (as opposed to cooling and solidifying quickly), thus allowing extensive lava flows to develop? select the two that apply.

magnesium; iron

part g: which of the following are examples of modern-day island arcs? choose all that apply.

mariana islands; aleutian islands

part b: volcanic ash is best described as which of the following?

microscopic pieces of rock ejected by a volcano

part d: where are continental volcanic arcs found?

on the overriding plate near a subduction zone

contrast pahoehoe and aa lava flows.

pahoehoe flows exhibit smooth surfaces, are hotter, and are more fluid than aa flows, which exhibit jagged surfaces with sharp edges.

what kind of volcanic hazard can be triggered by the collapse of a lava dome?

pyroclastic flow

choose the correct description of viscosity. under what conditions does magma have high viscosity?

resistance to flow. magma has a higher viscosity if it has a lower temperature, is rich in silica, and contains very few dissolved gases

what is scoria, and how does it differ from pumice?

scoria is a vesicular ejecta that is produced from mafic magma. although pumice is also vesicular, it differs from scoria in that pumice is felsic.

match the following pyroclastic materials in order from smallest to largest.

smallest: ash neither smallest or largest: lapilli largest: volcanic bombs

part d: which of the following has the single most immediate effect on lava's ability to solidify?

temperature

part b: which of the following is a present-day example of a continental rift?

the east african rift valley

which volcanic landform listed below is primarily composed of loose fragments of scoria?

the parícutin cinder cone

part e: based on the ages of the volcanic islands, in what direction was the tectonic plate moving toward?

toward the west

which type of volcanic hazard can decrease global temperatures?

volcanic ash

part c: what is a volcanic conduit called after the conduit has solidified and been exposed by erosion?

volcanic neck

part d: why are volcanic rocks often exposed at earth's surface as hills, ridges, and mountains surrounded by areas of lower elevation?

volcanic rocks are often more resistant to erosion than surrounding rock.

part a: which of the following features at yellowstone national park is evidence for a magma chamber beneath the park? choose all that apply.

welded tuff; rising (or bowing upward) ground near yellowstone river; geysers and hot springs (steam)