Explosive eruption

Definition

An explosive eruption is a volcanic eruption characterized by the violent expulsion of magma, gas, and volcanic ash into the atmosphere. This type of eruption is typically associated with high-viscosity magma that traps gas, leading to intense pressure buildup and a sudden release, resulting in an explosive release of materials.

5 Must Know Facts For Your Next Test

1. Explosive eruptions are often associated with stratovolcanoes, which have steep profiles and are built up by alternating layers of lava flows and tephra.
2. Magma composition plays a significant role in determining whether an eruption will be explosive; high silica content increases viscosity and gas retention.
3. The presence of water in magma can enhance explosivity, as it turns into steam, contributing to pressure buildup within the magma chamber.
4. During an explosive eruption, the ejected materials can reach heights of tens of kilometers into the atmosphere, affecting air travel and weather patterns.
5. Explosive eruptions can produce significant hazards such as ashfall, pyroclastic flows, and lahars, which can devastate surrounding areas and pose risks to life and infrastructure.

Review Questions

• How do the physical properties of magma influence the style of volcanic eruptions, particularly in relation to explosive eruptions?
  • The physical properties of magma, such as viscosity and gas content, greatly influence whether an eruption will be explosive or effusive. High-viscosity magma tends to trap gas bubbles, leading to increased pressure within the magma chamber. When this pressure becomes too great, it results in an explosive eruption as the gas escapes violently along with magma and other materials. Conversely, low-viscosity magma allows gas to escape more easily, resulting in less explosive eruptions.
• What types of volcanic landforms are typically associated with explosive eruptions and how do they differ from those formed by non-explosive eruptions?
  • Explosive eruptions are primarily associated with stratovolcanoes, which feature steep sides formed from layers of lava flows and pyroclastic deposits. These volcanoes exhibit a conical shape due to repeated explosive activity that builds up their structure. In contrast, shield volcanoes formed by non-explosive eruptions have gentle slopes created by low-viscosity lava flows that can travel long distances. This fundamental difference in landform structure highlights how eruption style directly influences volcanic landscape development.
• Evaluate the role of tectonic settings in determining the nature and frequency of explosive eruptions at specific locations around the globe.
  • Tectonic settings play a critical role in influencing both the nature and frequency of explosive eruptions. Subduction zones are particularly prone to explosive volcanism due to the interaction between oceanic and continental plates. The subducting plate releases water into the mantle, lowering melting points and generating magma with higher silica content. This leads to increased viscosity and gas retention, resulting in more frequent explosive eruptions compared to mid-ocean ridges or hot spots where lava tends to be less viscous and eruptions are predominantly effusive. Understanding these tectonic influences helps geologists predict volcanic activity in specific regions.

Related terms

pyroclastic flow: A fast-moving current of hot gas and volcanic matter that flows down the slopes of a volcano during an explosive eruption.

tephra: The collective term for all volcanic materials ejected during an explosive eruption, including ash, pumice, and volcanic rock fragments.

Volcanic Explosivity Index (VEI): A scale used to measure the explosiveness of volcanic eruptions, ranging from 0 to 8, based on the volume of tephra produced and the height of the eruption column.