Effusive Eruption

Definition

An effusive eruption is a volcanic event characterized by the relatively gentle outpouring of lava onto the Earth's surface, as opposed to explosive eruptions that propel ash and gas into the atmosphere. These eruptions often result in the formation of broad, shield volcanoes and extensive lava flows, primarily influenced by the viscosity of the magma and its chemical composition.

5 Must Know Facts For Your Next Test

1. Effusive eruptions are commonly associated with basaltic magma, which has low viscosity and allows lava to flow easily across the landscape.
2. Unlike explosive eruptions, effusive eruptions typically produce less ash and volcanic gases, making them less hazardous to surrounding areas in terms of immediate explosive risk.
3. The Kilauea volcano in Hawaii is a well-known example of a volcano that frequently experiences effusive eruptions, leading to extensive lava flows that create new land.
4. Effusive eruptions can lead to the formation of various landforms, such as lava tubes and pahoehoe (smooth) or aa (rough) lava surfaces.
5. Monitoring effusive eruptions is crucial for predicting potential hazards, as changes in the behavior of lava flows can impact nearby communities and ecosystems.

Review Questions

• How do the characteristics of magma influence the type of eruption that occurs at a volcano?
  • The characteristics of magma, particularly its viscosity and composition, play a crucial role in determining whether an effusive or explosive eruption will occur. Magma with low viscosity, like basaltic magma, allows gases to escape easily, resulting in effusive eruptions where lava flows out smoothly. In contrast, high-viscosity magma tends to trap gases, leading to increased pressure and explosive eruptions when the pressure is finally released.
• Compare and contrast effusive eruptions with explosive eruptions in terms of their geological features and potential hazards.
  • Effusive eruptions are characterized by the steady outflow of lava, creating features like shield volcanoes and extensive lava flows. They typically pose lower immediate risk compared to explosive eruptions, which can eject ash and pyroclastic materials violently into the atmosphere. Explosive eruptions may create stratovolcanoes with steep profiles due to their buildup from alternating layers of ash and lava. The hazards associated with explosive eruptions include ashfall, pyroclastic flows, and volcanic gas emissions, while effusive eruptions mainly threaten through advancing lava flows.
• Evaluate the environmental impacts of effusive eruptions on ecosystems and human settlements.
  • Effusive eruptions can have significant environmental impacts by altering landscapes through the creation of new landforms from solidified lava. While these eruptions typically present lower immediate threats than explosive ones, they can still affect ecosystems by changing habitats and water drainage patterns. Human settlements near active volcanoes must be vigilant; even slow-moving lava flows can cause destruction if they reach populated areas. Long-term impacts may include changes in soil composition and vegetation patterns as new land is formed.

Related terms

Lava Flow: The movement of molten rock (lava) that emerges from a volcano during an effusive eruption, which can travel great distances and reshape the landscape.

Viscosity:

A measure of a fluid's resistance to flow; in the context of magma, lower viscosity allows for more fluid lava to flow easily during effusive eruptions.

Shield Volcano: A type of volcano built up by the flow of low-viscosity lava, creating a broad, gently sloping structure typical of effusive eruptions.