Geology Chapter 10 Study Guide

Questions and Answers

What factors does the formation of magma depend on?

Heat, pressure, and water content.

Volcanoes that form far from plate boundaries form above what are called _____?

hot spots

What is the long belt of volcanoes that circles the Pacific Ocean called?

The Ring of Fire

What are the primary factors that determine whether a volcano erupts explosively or quietly?

Characteristics of the magma and the amount of dissolved gases in the magma. Signup and view all the answers

What is a volcanic vent?

An opening to the Earth's surface. Signup and view all the answers

Do all volcanic eruptions emit large amounts of gases?

True Signup and view all the answers

What are the three main volcanic types?

Shield volcanoes, cinder cones, and composite cones. Signup and view all the answers

How is decompression melting of rocks triggered?

When the pressure drops enough. Signup and view all the answers

What change allows rock melting to begin at convergent plate boundaries?

Water reducing the melting point. Signup and view all the answers

How many years have most 'hot spots' lasted?

Millions of years. Signup and view all the answers

What are particles ejected during a volcanic eruption called?

Pyroclastic material. Signup and view all the answers

What is the depression called that forms by the collapse of the top of a volcano?

Caldera Signup and view all the answers

What is the rock conduit called that remains when the surrounding cone has been eroded?

Volcanic neck. Signup and view all the answers

What is the wide area that forms when low-viscosity basaltic lava flows from fissures?

Lava plateau. Signup and view all the answers

What are the most dangerous volcanoes?

Composite volcanoes. Signup and view all the answers

What three characteristics are used to classify intrusive igneous bodies?

Size, shape, and relationship to surrounding rock layers. Signup and view all the answers

What is a sill?

When magma is injected along sedimentary bedding surfaces close to Earth's surface. Signup and view all the answers

What is a laccolith?

When magma is injected between sedimentary layers close to Earth's surface and collects as a lens-shaped mass. Signup and view all the answers

What is a dike?

When magma from a large magma chamber invades fractures in the surrounding rocks. Signup and view all the answers

What is a batholith?

A large intrusive igneous body with an area greater than 100 km2 exposed at the surface. Signup and view all the answers

How is temperature related to viscosity?

The temperature of the magma determines the magma's viscosity. Signup and view all the answers

What is the most abundant gas associated with volcanic activity?

Water vapor. Signup and view all the answers

How do we classify igneous bodies?

By size, shape, and relationship to surrounding rock layers. Signup and view all the answers

What is pyroclastic flow?

A scorching mixture of glowing volcanic particles and gases that sweeps rapidly down a volcano's flanks. Signup and view all the answers

What is pahoehoe flow?

A hotter, fast-moving basaltic lava that forms a smooth skin that wrinkles as the still-molten subsurface lava continues to flow. Signup and view all the answers

What is aa flow?

Aa flow is a cooler, slow-moving basaltic lava that forms a surface of rough, jagged blocks with sharp, spiny projections. Signup and view all the answers

What are volcanic bombs?

Pyroclastic particles that are larger than 64 millimeters in diameter that are ejected from the volcano as glowing lava. Signup and view all the answers

What are cinders?

Particles ejected during an eruption that range in size from small beads to walnut size. Signup and view all the answers

What is a lahar?

Mudflow made up of water-soaked volcanic ash and rock. Signup and view all the answers

What is a volcanic block?

Pyroclastic particles that are larger than 64 millimeters in diameter that are made of hardened lava. Signup and view all the answers

What are the three types of boundaries associated with volcanism?

Convergent, divergent, and intraplate boundary. Signup and view all the answers

What is a shield volcano?

It's magma type is a fluid basaltic lava, has a broad shape, slightly domed in structure that resembles a warrior's shield. Signup and view all the answers

What is a cinder cone volcano?

It's magma type is a gas-rich basaltic or rhyolitic magma, it has a cinder cone with 30' to 40' steep slopes and usually has a single eruption that can last from 2 weeks to a few years. Signup and view all the answers

Study Notes

Magma Formation and Eruption Types

Formation of magma relies on heat, pressure, and water content.
Volcanoes distant from plate boundaries emerge over "hot spots" in the crust.
The characteristics of magma and gas content dictate whether eruptions are explosive or gentle.
Most volcanic eruptions release significant gas quantities.

Volcano Classification and Evolution

The three primary volcanic types: shield volcanoes, cinder cones, and composite cones.
Decompression melting occurs when the pressure on rocks decreases sufficiently.
Water's presence at convergent boundaries lowers melting points, facilitating rock melting.

Volcanic Structures and Features

A volcanic vent is an opening to the Earth's surface where eruptions occur.
Particles emitted during eruptions range from fine dust to large fragments, termed pyroclastic material.
The depression formed by a volcano's collapse is known as a caldera.
Erosion of the surrounding cone leaves behind a rock conduit called a volcanic neck.

Lava and Igneous Bodies

Low-viscosity basaltic lava creates vast lava plateaus when erupted from fissures.
Composite volcanoes are recognized as the most hazardous volcanic type.
Intrusive igneous bodies classified by size, shape, and their relation to surrounding rock, include sills, laccoliths, dikes, and batholiths.

Lava Flows and Volcanic Products

Pahoehoe lava flows are fast, hot, and smooth, forming a wrinkled surface as the underlying lava continues to flow.
Aa lava flows move slower, cooler, and create a rough surface with sharp projections.
Pyroclastic flows contain rapidly moving, hot volcanic particles and gases.
Volcanic bombs are large pyroclastic ejecta exceeding 64 mm in diameter, expelled as glowing lava.

Additional Volcanic Terms

Cinders are small pyroclastic particles ejected during eruptions, ranging from bead to walnut sizes.
Lahars are destructive mudflows composed of water-saturated volcanic ash and rocky debris.
Volcanic blocks are hardened lava fragments larger than 64 mm.

Tectonic Boundaries and Their Impact

Volcanism occurs at three primary boundary types: convergent, divergent, and intraplate.
Shield volcanoes feature fluid basaltic lava, creating broad, dome-like structures resembling a warrior's shield.
Cinder cone volcanoes, with steep slopes, typically result from gas-rich basaltic or rhyolitic magma and can erupt for weeks to years.

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This quiz focuses on key concepts from Geology Chapter 10, detailing the formation of magma, hot spots, and volcanic regions like the Ring of Fire. Use these flashcards to reinforce your understanding of volcanic activity and tectonic processes.