Geology HW 07: Volcanoes

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Questions and Answers

Which of the following are types of volcanoes? (Select all that apply)

Shield volcano (correct)

Composite volcano (correct)

Cinder Cone (correct)

Dome

What information do geologists use to classify volcanoes?

Shape and type of deposits

Cinder cones are made of ________.

pyroclastic deposits

In general, how often do most cinder cones erupt?

Most cinder cones erupt once. Signup and view all the answers

What are shield volcanoes generally made of?

Basalt flows Signup and view all the answers

What is the range of shield volcano height?

300 to 10,000 meters Signup and view all the answers

What are composite volcanoes made of?

Basalt flows, pyroclastic deposits Signup and view all the answers

Why are shield volcanoes wider than composite volcanoes?

The lava that flows out of shield volcanoes is more fluid than the lava that flows out of composite volcanoes. Signup and view all the answers

What type of magma erupts out of dome complexes?

Felsic magma Signup and view all the answers

What type of volcanoes are the tallest?

Shield volcanoes Signup and view all the answers

What is the range of dome complex height?

500 to 2,000 meters Signup and view all the answers

In which of the following lava types would you expect to see the development of pahoehoe?

Basaltic Signup and view all the answers

In which of the following lava types would you expect to find the greatest percentage of gases?

Rhyolitic Signup and view all the answers

In which of the following types of lavas would you expect to find the greatest production of pyroclastic material?

Rhyolitic Signup and view all the answers

What do we call pyroclastic material, ejected during a volcanic eruption, composed of incandescent lava that is greater than 64 millimeters (2.5 inches) in diameter?

Bombs Signup and view all the answers

Which of the following gases is most abundant in basaltic lavas?

Water vapor Signup and view all the answers

At which of the following tectonic settings would you expect to find volcanoes producing the highest volumes of pyroclastic material?

Subduction of an oceanic plate under a continental plate Signup and view all the answers

At which of the following tectonic settings would you expect to find volcanoes producing significant amounts of very fluid, high-temperature lavas?

Mantle plumes Signup and view all the answers

Which of the following would best describe the shape and composition of a volcano in the Cascade Range?

Cone-shaped volcano with alternating layers of lava and pyroclastic material Signup and view all the answers

Which of the following statements describe a part of the process of the formation of the Cascade Mountain Range?

Rising of magma to the surface, Partial melting due to the presence of water, Eruption of material at the surface Signup and view all the answers

Which of the following volcanoes is associated with the Ring of Fire?

Mt. Pinatubo Signup and view all the answers

Which of the following features at Yellowstone National Park is evidence for a magma chamber beneath the park?

Rising (or bowing upward) ground near Yellowstone River, Welded tuff, Geysers and hot springs (steam) Signup and view all the answers

Which of the following pieces of evidence for a past volcanic eruption are present at Yellowstone National Park?

Pyroclastic material, Lava flows, A caldera rim Signup and view all the answers

Yellowstone is best described as which of the following?

An active volcano that has erupted in the last 1 million years Signup and view all the answers

Which of the following was a stage in the formation of Yellowstone caldera?

Crust bows upward above a magma chamber. Signup and view all the answers

What is the term for a tabular igneous pluton that occurs in an orientation that is discordant with the bedding surfaces of adjacent sedimentary rocks?

Dike Signup and view all the answers

What is the term for a tabular igneous pluton that occurs in an orientation that is concordant with the bedding surfaces of adjacent sedimentary rocks?

Sill Signup and view all the answers

Which of the following terms is best described as a massive pluton?

Batholith Signup and view all the answers

Batholiths are known to form the cores of mountain ranges such as the Sierra Nevada. What is the implication of this observation?

Because batholiths form deep within Earth, the occurrence of one at the surface implies that it has since been uplifted and/or the rocks above have been removed. Signup and view all the answers

While working in the field, you find a dike cutting across some sedimentary rocks. What grain size would you expect to find in this pluton?

Fine-grained Signup and view all the answers

When will magma rise to Earth's surface?

When the magma is less dense than adjacent rock Signup and view all the answers

In general, when will melted rock in the mantle rise?

Almost always Signup and view all the answers

How are felsic magmas formed?

Heat from the mantle melts part of the lower crust. Signup and view all the answers

In general, why does Earth's crust sit on top of the mantle?

Earth's crust is less dense than the mantle. Signup and view all the answers

How do mafic volcanic rocks get to Earth's surface?

Pressure from overlying crust forces mantle magmas through cracks to Earth's surface. These magmas erupt out of volcanoes, cool, and solidify into rock. Signup and view all the answers

What type of volcanism characterizes the Ring of Fire? (Select all that apply)

Volcanism caused by convergent oceanic-oceanic boundaries Signup and view all the answers

What type of boundary is present along the eastern boundary of the North American plate?

Divergent oceanic-oceanic Signup and view all the answers

At what tectonic setting is Hawaii located?

Oceanic hot spot Signup and view all the answers

What drives melting at divergent boundaries?

Decompression melting Signup and view all the answers

Which of the following tectonic settings does NOT produce volcanism?

Transform boundary Signup and view all the answers

Study Notes

Types of Volcanoes

Shield volcanoes are characterized by broad, gently sloping sides and are primarily composed of basalt flows.
Composite volcanoes feature steep sides with alternating layers of lava and pyroclastic deposits.
Cinder cone volcanoes are comprised of pyroclastic deposits and generally erupt once.

Volcano Classification

Geologists classify volcanoes by examining their shape and the types of deposits they produce.

Lava Composition and Eruptions

Cinder cones consist of pyroclastic materials and typically erupt only one time.
Shield volcanoes are constructed from fluid basalt flows, contributing to their wider shape compared to composite volcanoes.
Composite volcanoes are made of both basalt flows and pyroclastic materials.

Volcano Height and Structure

Shield volcanoes can reach heights between 300 to 10,000 meters, making them some of the tallest types of volcanoes.
Dome complexes generally range in height from 500 to 2,000 meters.

Lava Types and Characteristics

Pahoehoe lava forms from basaltic flows, resulting in smooth, ropy textures.
Rhyolitic lava contains the highest percentage of gases and is associated with significant pyroclastic material production.

Volcanic Ejecta

Pyroclastic material ejected during eruptions includes "bombs," which are larger than 64 mm in diameter.
Water vapor is the most common gas found in basaltic lavas.

Tectonic Settings and Volcanism

High volumes of pyroclastic material are typically found at subduction zones, where an oceanic plate is forced under a continental plate.
Oceanic hot spots, like Hawaii, produce fluid, high-temperature lava.

Cascade Range and Yellowstone

The Cascade Range features cone-shaped volcanoes with layers of lava and pyroclastic materials.
The formation of the Cascade Mountains involves rising magma, partial melting due to water, and surface eruptions.
Yellowstone National Park exhibits signs of a magma chamber beneath it, such as rising ground, welded tuff, and geysers.

Different Plutons

A dike is a tabular igneous pluton that cuts across sedimentary rock layers, while a sill runs parallel to bedding surfaces.
Batholiths are massive plutons found in mountain ranges, indicating past uplift and erosion.

Magma Behavior

Magma rises when it is less dense than surrounding rock, and mantle melting often causes this process.
Felsic magmas form when heat from the mantle melts parts of the lower crust, allowing them to rise.

Tectonic Analyses

The eastern boundary of the North American plate is a divergent oceanic-oceanic boundary.
Volcanism occurs along convergent boundaries (both oceanic-continental and oceanic-oceanic) and not along transform boundaries.
Decompression melting drives the melting process at divergent boundaries.

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Description

Test your knowledge of volcano types and classifications with this Geology homework quiz. Explore the characteristics of shield volcanoes, composite volcanoes, and cinder cones, as well as how geologists differentiate between them. Perfect for reinforcing essential concepts in volcanic geology.