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6.29: Volcanic Landforms

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Why is the Republic of Indonesia made of 17,508 islands?

Around the Pacific Rim is Indonesia, a nation built from the dotted volcanoes of an island arc. Indonesia is distinctive for its rich volcanic soil, tropical climate, tremendous biodiversity, and volcanoes. These volcanoes are in Java, Indonesia.

Landforms from Lava

Volcanoes and Vents

The most obvious landforms created by lava are volcanoes, most commonly as cinder cones, composite volcanoes, and shield volcanoes. Eruptions also take place through other types of vents, commonly from fissures ( Figure below ). The eruptions that created the entire ocean floor are essentially fissure eruptions.

A fissure eruption on Mauna Loa in Hawaii travels toward Mauna Kea on the Big Island.

Lava Domes

Viscous lava flows slowly. If there is not enough magma or enough pressure to create an explosive eruption, the magma may form a lava dome . Because it is so thick, the lava does not flow far from the vent. ( Figure below ).

Lava domes are large, round landforms created by thick lava that does not travel far from the vent.

Lava flows often make mounds right in the middle of craters at the top of volcanoes, as seen in the Figure below .

Lava domes may form in the crater of composite volcanoes as at Mount St. Helens

Lava Plateaus

A lava plateau forms when large amounts of fluid lava flow over an extensive area ( Figure below ). When the lava solidifies, it creates a large, flat surface of igneous rock.

Layer upon layer of basalt have created the Columbia Plateau, which covers more than 161,000 square kilometers (63,000 square miles) in Washington, Oregon, and Idaho.

Land

Lava creates new land as it solidifies on the coast or emerges from beneath the water ( Figure below ).

Lava flowing into the sea creates new land in Hawaii.

Over time the eruptions can create whole islands. The Hawaiian Islands are formed from shield volcano eruptions that have grown over the last 5 million years ( Figure below ).

The island of Hawaii was created by hotspot volcanism. You can see some of the volcanoes (both active and extinct) in this mosaic of false-color composite satellite images.

Landforms from Magma

Magma intrusions can create landforms. Shiprock in New Mexico is the neck of an old volcano that has eroded away ( Figure below ). The volcanic neck is the remnant of the conduit the magma traveled up to feed an eruption.

The aptly named Shiprock in New Mexico.

Summary

  • Landforms created by lava include volcanoes, domes, and plateaus.
  • New land can be created by volcanic eruptions.
  • Landforms created by magma include volcanic necks and domes.

Practice

Use this resource to answer the questions that follow.

1. What type of lava is produced by volcanoes?

2. How did the columns in the video form?

3. How was Fingal's cave formed?

4. Describe how the basalt lava flows?

5. How does basalt behave when it has a lot of gas trapped within it?

Review

1. What is Shiprock and how did it form?

2. How do lava plateaus form?

3. What types of landforms are created by very viscous magma?

Vocabulary

lava dome

lava dome

A dome-shaped plug of viscous lava that cools near the vent of a volcano.
lava plateau

lava plateau

A flat area formed by the eruption of large amounts of fluid lava.

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At Grade

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Date Created:

Feb 24, 2012

Last Modified:

Sep 23, 2014
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