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What is Extrusive Volcanism?

When hot lava comes out of a volcano and touches the ground. Molten rock bursts forth, shaping our world.

Indonesia is a part of the Pacific Ring of Fire and has the most number of extrusive volcanoes in the world. We all have read about active, dormant, and sleeping volcanoes, but what is extrusive volcanism? You know extrusive volcanism plays an important role in shaping the surface and influencing the geological activity of the Earth. Extrusive volcanism is an important geological process that involves the eruption of molten rock or lava onto the Earth’s surface.  Let us find out more about it in detail along with its features and types.

1. What Extrusive Means?

Extrusive refers to rocks, minerals, and other materials that form when molten material from the Earth’s interior is forced onto its surface. This molten material is typically referred to as lava or magma and, upon cooling, forms different types of igneous-extrusive rocks like basalt and andesite.

Extrusive also includes materials thrown out into the air from a volcanic eruption, such as tephra or ash. The extrusion process happens quite quickly in comparison to other geological processes, so these new materials tend to be able to preserve their features since they cool much faster than intrusive formations like granite. But what is extrusive volcanism?

2. What are Extrusive Bodies?

Extrusive bodies are igneous rocks generated by volcanism, as magma intervenes in the Earth’s uppermost crust and cools rapidly. Extrusive bodies form the surface expressions of volcanic activity – from small-scale ash plumes to massive shield volcanoes rising high into the sky.

3. What is Extrusive Volcanism?

Extrusive volcanism is the process by which molten magma is rapidly ejected from the Earth’s upper mantle and then solidifies on the planet’s surface. This creates earthly landforms such as lava flow, ignimbrite, and pyroclastic material.

These volcanic materials can become mountains or piles of volcanic ash depending on the composition and other conditions present during the eruption. Observations near volcanoes can give insight into how past eruptions have shaped local landscapes and our understanding of underlying geologic processes.

The most common extrusive volcanism rock is basalt. Consequently, it is speculated that these rocks were produced by early volcanic episodes and later spread along the seafloor by plate tectonics. Have you ever wondered Why do people live near Volcanoes?

4. How Extrusive Volcanoes are Formed?

Extrusive volcanoes are formed when hot lava flows from an erupting volcano onto the Earth’s surface. This type of volcanic activity typically involves felsic, or silica-rich magma.

When this type of magma is exposed to cooler temperatures at the Earth’s surface, it rapidly cools and solidifies, forming volcanic rocks and landforms. The rapid cooling of the lava also causes air bubbles to become trapped within the solidified rock.

5. What are Intrusive and Extrusive Landforms?

After learning what is extrusive volcanism let us find out about what type of landform it forms. Intrusive and extrusive landforms are terms used in geology to describe specific forms of terrain generated by volcanic activity.

Extrusive landforms are formed when molten magma is ejected onto the Earth’s surface, while intrusive landforms are created when magma cools and solidifies beneath the terrestrial crust.

The result of such processes can range from imposing structures like cinder cones and lava domes to much more subtle features, such as columns, batholiths and diabase sheets. Come find out about What are Underwater Mountain Ranges?

6. What are the Characteristics of Extrusive Volcanism?

JAN23 What is Extrusive Volcanism 2

The characteristics and extrusive volcanic features examples are as follows:

  • Extrusive volcanic features are formed when molten magma from inside the Earth is expelled onto its surface, resulting in landforms such as lava flows, pyroclastic debris, and volcanic bombs.
  • Extrusive volcanic rock is characterized by the rapid cooling of lava that erupts from a volcano.
  • This type of activity produces volcanic rocks with small crystals, such as basalt and rhyolite, which have a fine-grained texture.
  • Extrusive volcanism typically creates steep-sided mountains or cones due to the thick layers of cooled lava.
  • The eruptions are explosive and form pyroclastic flows, which consist of ash, dust and other materials blasted from the volcano during an eruption along with gases like nitrogen compounds, Sulphur compounds, and trace amounts of chlorine, hydrogen, and argon.

7. What are the Two Types of Volcanism?

After learning about what is extrusive volcanism, get to know about the two types of volcanism.

  • A stratovolcano: It is a steep, conical-shaped volcano composed of many layers of hardened lava, tephra, and volcanic ash.
  • A shield volcano: A broad dome-shaped volcano made up of thin layers of basaltic lava flows. Both types can produce violent eruptions with devastating consequences for nearby communities and the environment.

Also do not forget to read about 10 Types of Beach Stones.

8. What are the Three Types of Extrusive Volcanism?

There are three classic types of extrusive volcanism: cinder cone volcanoes, composite volcanoes (stratovolcanoes), and shield volcanoes. 

  • Cinder cone volcanoes are composed of smaller fragments of rock called cinders that build up around the volcano’s mouth, creating a taller peak.
  • Composite volcanoes consist of alternating layers of hardened lava, ash, and other residue that builds up slowly over time to create even higher peaks than cinder cones.
  • Shield volcanoes are large, low-slope mounds made of accumulated layers of solidified basaltic lava flows created by repeated eruptions over long periods.

9. What is the Texture of Extrusive Volcanic Rock?

Extrusive volcanic rocks typically have an aphanitic texture, meaning that the crystals are too small to be seen with the naked eye. This is due to the rapid cooling of magma during its ascent to the surface. This results in small fine-grained crystals within these rocks

The answer to what is extrusive volcanism is a fascinating geological process that can have devastating consequences. While we often think of volcanoes as giant mountains, they come in all shapes and sizes. Some are even underwater! By understanding how types of extrusive volcanism work, we can better prepare for eruptions and protect people and property from the harmful effects of lava flows. (Also read What are Drawbacks of Urbanization?)


Written by Jack Williams

Jack Williams is a multifaceted lifestyle writer who has a passion for bringing interesting and enlightening content to his readers. With a strong background in researching and writing, he has made a name for himself in the world of lifestyle journalism, covering a wide range of topics including Wikipedia, facts, and trivia.

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