Fissure eruptions

Definition

Fissure eruptions are volcanic events where magma escapes to the Earth's surface through linear fractures or cracks in the crust, rather than a single volcanic vent. These eruptions often produce extensive lava flows that can cover large areas and are typically associated with divergent plate boundaries, where tectonic plates are moving apart, allowing magma to rise easily from the mantle.

5 Must Know Facts For Your Next Test

1. Fissure eruptions usually produce basaltic lava, which is low in viscosity, allowing it to flow more easily over large distances.
2. These eruptions can occur in long, linear cracks, sometimes stretching several kilometers, and can create vast lava fields.
3. The lava produced from fissure eruptions often forms features like pahoehoe (smooth, ropy lava) and aa (rough, jagged lava), depending on its cooling rate and gas content.
4. Fissure eruptions are common along mid-ocean ridges, where tectonic plates are separating and magma rises to fill the gap.
5. Unlike explosive eruptions, fissure eruptions generally have a lower level of explosivity, making them less hazardous to nearby populations.

Review Questions

• How do fissure eruptions differ from other types of volcanic eruptions, and what implications does this have for their formation?
  • Fissure eruptions differ from other types of volcanic eruptions primarily by the way magma is released; instead of erupting through a single vent, it emerges through cracks in the Earth’s crust. This method of eruption allows for the continuous flow of lava over wide areas without the explosive pressure buildup found in stratovolcanoes. As a result, fissure eruptions can create extensive lava fields rather than forming traditional conical volcano shapes.
• Discuss the geological features associated with fissure eruptions and how they contribute to our understanding of volcanic activity at divergent plate boundaries.
  • Geological features associated with fissure eruptions include extensive lava fields and specific formations like rift valleys and shield volcanoes. These features help scientists understand the processes occurring at divergent plate boundaries, where tectonic plates move apart. The presence of linear cracks indicates areas where magma can easily ascend, providing insights into tectonic movements and the formation of new crust as lava solidifies and expands outward.
• Evaluate the environmental impact of fissure eruptions compared to explosive volcanic events in terms of both immediate effects and long-term consequences.
  • Fissure eruptions typically have a different environmental impact compared to explosive volcanic events. While fissure eruptions result in widespread but less immediate dangers like lava flow inundation, explosive events can lead to ash clouds that affect air quality and climate on a larger scale. Long-term consequences may include changes to landforms and ecosystems; fissure eruptions can create new habitats as they cover old ones with lava, while explosive eruptions might lead to more drastic alterations in landscape due to pyroclastic flows and ash deposition.

Related terms

lava flows:

Lava flows are streams of molten rock that emerge from a volcano during an eruption, spreading out over the ground as they cool and solidify.

divergent plate boundaries: Divergent plate boundaries are regions where two tectonic plates are moving away from each other, allowing magma to rise and create new crust.

basaltic magma:

Basaltic magma is low-viscosity magma that is rich in iron and magnesium, leading to fluid lava flows typically associated with fissure eruptions.