Effusive eruptions

Definition

Effusive eruptions are volcanic eruptions characterized by the gentle flow of lava onto the surface, rather than explosive ejections of ash and gases. These eruptions typically occur at shield volcanoes and along divergent plate boundaries, where magma is low in viscosity and allows for the relatively smooth escape of lava. The nature of effusive eruptions leads to the formation of extensive lava plateaus and can create new landforms over time.

5 Must Know Facts For Your Next Test

1. Effusive eruptions are most common at shield volcanoes like Mauna Loa in Hawaii, where the lava flows can travel long distances.
2. The lava produced in effusive eruptions is typically basaltic, which has a low viscosity, allowing it to flow easily.
3. Effusive eruptions can create significant landforms such as lava tubes and extensive lava fields, contributing to landscape evolution.
4. In contrast to explosive eruptions, effusive events are generally less dangerous to nearby populations due to their predictable flow patterns.
5. The behavior of an effusive eruption can be influenced by the amount of gas dissolved in the magma; lower gas content typically leads to less explosive activity.

Review Questions

• How do the characteristics of effusive eruptions differ from those of explosive eruptions?
  • Effusive eruptions are characterized by the gentle outpouring of lava, leading to slow-moving lava flows and the formation of extensive landforms like lava plateaus. In contrast, explosive eruptions involve violent blasts that eject ash, gases, and fragmented rock into the atmosphere. The differences stem from magma composition and viscosity; effusive eruptions typically occur with low-viscosity basaltic magma, while explosive eruptions often involve more viscous and gas-rich magma.
• Discuss the role of divergent plate boundaries in facilitating effusive eruptions.
  • Divergent plate boundaries are critical for effusive eruptions because they allow tectonic plates to pull apart, creating spaces for magma to rise easily from the mantle. This upward movement of magma often results in low-viscosity basaltic lava flowing out onto the surface without significant pressure buildup. As these lava flows accumulate over time, they can form large shield volcanoes or extensive lava fields characteristic of effusive volcanic activity.
• Evaluate how understanding effusive eruptions contributes to volcanic hazard assessment in regions near shield volcanoes.
  • Understanding effusive eruptions is crucial for volcanic hazard assessment because it helps predict lava flow behavior and potential impacts on nearby communities. By studying past effusive events at shield volcanoes, scientists can determine likely flow paths and areas at risk, allowing for better planning and response strategies. Additionally, recognizing factors such as gas content in magma can aid in forecasting changes that might lead to more hazardous explosive behavior. This knowledge ultimately enhances public safety and preparedness in volcanically active regions.

Related terms

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

Magma Viscosity: The measure of a fluid's resistance to flow, which significantly affects the style of a volcanic eruption.

Divergent Plate Boundaries: Regions where tectonic plates move apart, allowing magma to rise and often resulting in effusive eruptions.