Effusive eruption

Definition

An effusive eruption is a volcanic event characterized by the gentle flow of low-viscosity lava, which results in the formation of broad, shield-shaped volcanoes. These eruptions are generally less explosive than other types, allowing lava to spread out over large areas, creating distinct landforms and contributing to the landscape's evolution.

5 Must Know Facts For Your Next Test

1. Effusive eruptions typically occur at hotspots or along divergent tectonic plate boundaries where magma rises easily to the surface.
2. The lava produced during effusive eruptions is often basaltic in composition, which has a low silica content and contributes to its fluid nature.
3. Unlike explosive eruptions that can produce pyroclastic flows and ash clouds, effusive eruptions primarily emit lava flows and gases.
4. Effusive eruptions can build large volcanic features like shield volcanoes, which can cover hundreds of square kilometers with their gently sloping flanks.
5. The frequency and duration of effusive eruptions can vary widely; some volcanoes may have continuous lava flow for years, while others may erupt sporadically.

Review Questions

• Compare and contrast effusive eruptions with explosive eruptions in terms of magma characteristics and eruption outcomes.
  • Effusive eruptions involve low-viscosity lava that flows smoothly and steadily from a volcano, often resulting in the formation of shield volcanoes. In contrast, explosive eruptions are characterized by high-viscosity magma that traps gas, leading to violent explosions and the ejection of ash and pyroclastic material. The differences in magma composition—basaltic for effusive eruptions versus andesitic or rhyolitic for explosive ones—result in distinct landforms and eruption dynamics.
• Discuss how tectonic settings influence the style of volcanic eruptions, particularly regarding effusive eruptions.
  • Tectonic settings play a crucial role in determining eruption styles. Effusive eruptions are commonly found at divergent plate boundaries, such as mid-ocean ridges or hotspots, where magma rises easily due to lower pressure. In these regions, the tectonic environment allows for the generation of low-viscosity basaltic magma that promotes gentle lava flows. Conversely, convergent plate boundaries often produce more explosive eruptions due to higher viscosity magma that accumulates gas pressure before erupting violently.
• Evaluate the environmental impacts of effusive eruptions on landforms and ecosystems over time.
  • Effusive eruptions have significant long-term effects on landforms and ecosystems. The gradual flow of lava creates extensive shield volcanoes that reshape the landscape over time. As these flows cool and solidify, they contribute to soil formation through weathering processes. Additionally, new landforms can create diverse habitats that support various ecosystems. Over time, these environments may adapt to changes in topography and substrate composition brought about by repeated effusive activity, influencing biodiversity and ecological succession.

Related terms

Lava Flow: The molten rock that erupts from a volcano and flows across the ground, which can vary in speed and consistency depending on its viscosity.

Shield Volcano: A type of volcano built primarily by the flow of low-viscosity lava, resulting in a broad, gently sloping structure.

Viscosity:

A measure of a fluid's resistance to flow, which influences how easily lava can move during an eruption.