Geology Test 1 CH 5

crater

A_____________is formed on the volcano summit by explosive eruptions and is composed of accumulated volcanic debris.

Conduit

All types of volcanic cones share which feature?

Convergent boundary

Along which tectonic boundary will chains of composite cone volcanoes be located?

Divergent boundaries: magma produced by decompression melting

Along which tectonic boundary would the greatest amount of magma be generated every year? Why?

Yellowstone

An example of a volcanic caldera that formed from the collapse of a magma chamber after large volumes of material were erupted is ________.

Kilauea

Around which volcano is a scientist likely find pillow basalts?

Stratovolcanoes

Composite cones are also known as _____________________

caldera

Depletion of the upper part of a magma chamber during a volcanic eruption can result in gravitational collapse of the volcanic summit to form a ___________

They are old dikes radiating from the main neck of the volcano.

How did the ridges around Shiprock form?

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.

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

Fluids are dehydrated out of the descending plate, which lowers the melting point of the surrounding mantle.

How is magma generated along subduction zones?

basaltic

In order to cover such large expanses of seafloor, shield volcanoes erupt ________ lava.

intraplate volcanism

Kilauea is a volcano created by ________.

Silica

Lavas erupting from composite cones are generally ________-rich, making them very viscous.

Magma

Molten rock found at depth that contains dissolved gases and some crystals

Cinder cones are generally the product of a single eruption and thus are constructed in less than a year or less than a month.

Over what time span do most typical cinder cones form?

Andesitic and rhyolitic

Pyroclastic materials are generally associated with which type of magma(s)?

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.

discover precursors that may warn of an impending or imminent eruption.

Scientists monitor volcanoes in an attempt to

False

T/F: The more the silica in magma, the lower the viscosity.

Volcanic cone

A ________ is a cone-shaped structure created by successive eruptions of volcanic materials such as lava or pyroclastic materials.

seamount

A ________ is a submarine volcano.

crater;caldera

A ___________ is a small, funnel-shaped depression; a ___________ is a large depression that has a diameter of over 1 km.

magma chamber

A ________________ results when magma collects or ponds due to its density being higher than that of overlaying materials.

parasitic cone

A _________________is a small cone on the side or base of a volcano that has formed during repeated flank eruptions.

vent

A ___________is an opening where volcanic materials erupt at the Earth's surface, and can form on the flanks of a larger volcano in the case of a parasitic cone.

conduit

The pipelike feature through which magma travels upward from an underground magma chamber is called a ____________

-Melting caused by decompression -Outpourings of lava/magma originating from the mantle.

The production of magma (magmatism) at divergent boundaries is characterized by...

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

The volcanoes in the Ring of Fire are generally described as

Microscopic pieces of rock ejected by a volcano

Volcanic ash is best described as...

decompression melting

What drives melting at divergent boundaries?

The rocks in Shiprock formed when magma solidified in the neck of an old volcano.

What geologic event led to the formation of the rocks that make up Shiprock?

a mudflow of volcanic debris saturated with water

What is a lahar?

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.

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

Gravity

What is the driving force behind pyroclastic flows?

Mantle Plumes

What is the source of magma for most intraplate volcanism?

Low viscosity

What kind of viscosity would flood basalts have?

Composite cone

What kind of volcano is most closely associated with pyroclastic flows?

Andesite

What kind(s) of lava are most closely associated with composite cones?

Transform boundaries

What tectonic settings does NOT produce volcanism?

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

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

Basaltic

What type of lava is produced at a divergent plate boundary?

Basaltic

Which lavas make up 90 percent of the total volume of lava on Earth?

Aa flows have sharp, jagged edges.

Which of the following is a feature of an aa flow? Aa flows can change into pahoehoe lava. Aa flows can develop lava tubes. Aa flows can produce pillow lavas. As flows have sharp, jagged edges.

Conduit

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

Cinder cones are composed of generally basaltic pyroclastic material and scoria.

Which of the following statements accurately describes the composition of a cinder cone?

Lava

Which of the following volcanic materials flows out of a volcanic vent?

an increase in temperature

Which of the following would decrease the viscosity of magma? an increase in temperature a decrease in dissolved gases an increase in silica content a decrease in water content a decrease in the slope of the volcanic flank

Basaltic and andesitic

Which type of magma(s) will produce scoria?

Volcanic ash

Which type of volcanic hazard can decrease global temperatures?

cinder cones

Which volcanoes have flanks with the steepest angle of repose (between 30° and 40°)?

Shield

With the exception of volcanoes associated with a subduction zone, most volcanic islands are ________ volcanoes.

high viscosity (rhyolitic) lava

_____ is/are common in the final stages of growth of a typical shield volcano.

Fumaroles

________ are small vents that emit volcanic gases.

Pyroclastic material

________ is pulverized rock, lava fragments, and ash erupted from a volcano.

Lapilli

_____________are pyroclastic material that have diameters between 2 and 64 mm.