Shield Volcanoes

Definition

Shield volcanoes are a type of volcano characterized by their broad, gently sloping profiles, which resemble the shape of a warrior's shield. These volcanoes are formed by the accumulation of highly fluid, basaltic lava flows that spread out in all directions, creating a wide, shallow structure.

5 Must Know Facts For Your Next Test

1. Shield volcanoes are the largest type of volcano, with bases that can extend for hundreds of kilometers and heights that can reach several kilometers.
2. The gentle slopes of shield volcanoes, typically ranging from 3 to 10 degrees, are a result of the highly fluid nature of the basaltic lava that erupts from them.
3. Shield volcanoes are often associated with hotspots, which are fixed sources of magma in the Earth's mantle that can create a series of shield volcanoes as the Earth's crust moves over them, such as the Hawaiian Islands.
4. The eruptions of shield volcanoes are typically effusive, meaning the lava flows out of the volcano gently and steadily, rather than explosively.
5. Shield volcanoes are generally considered less hazardous than other types of volcanoes, such as stratovolcanoes, due to their less violent eruption styles and the ability of their broad slopes to accommodate lava flows.

Review Questions

• Explain the relationship between the fluid nature of basaltic lava and the broad, gently sloping profile of shield volcanoes.
  • The broad, gently sloping profile of shield volcanoes is a direct result of the highly fluid nature of the basaltic lava that erupts from them. Basaltic lava has a relatively low viscosity, meaning it flows easily and can spread out in all directions, creating a wide, shallow structure rather than a steep, narrow one. This allows the lava to accumulate over time, gradually building up the volcano's characteristic shield-like shape.
• Describe the role of hotspots in the formation of shield volcanoes and provide an example of a shield volcano formed by a hotspot.
  • Hotspots, which are fixed, stationary sources of magma in the Earth's mantle, play a crucial role in the formation of shield volcanoes. As the Earth's crust moves over a hotspot, a series of shield volcanoes can be created, such as the Hawaiian Islands. The Hawaiian shield volcanoes, including Mauna Loa and Kilauea, are prime examples of volcanoes formed by a hotspot, where the fixed magma source has produced a chain of these broad, gently sloping volcanic structures as the Pacific tectonic plate has moved over it.
• Analyze the differences in eruption styles and hazards between shield volcanoes and other types of volcanoes, such as stratovolcanoes, and explain the implications for human populations living near these volcanic features.
  • Shield volcanoes, with their effusive eruption styles and gentle slopes, are generally considered less hazardous than other types of volcanoes, such as stratovolcanoes, which are more prone to explosive eruptions. The fluid, basaltic lava of shield volcanoes tends to flow steadily rather than violently, and their broad slopes can often accommodate lava flows, reducing the immediate threat to nearby populations. In contrast, stratovolcanoes, with their steeper slopes and more viscous, silica-rich magmas, are more likely to produce explosive eruptions that can send ash and pyroclastic flows over large areas, posing a greater risk to human settlements. This difference in eruption style and hazard level has important implications for the development and safety of communities living in the vicinity of these volcanic features.

Related terms

Basaltic Lava: Basaltic lava is a type of lava that is relatively low in viscosity, allowing it to flow more easily and create the broad, gently sloping profiles of shield volcanoes.

Effusive Eruptions: Effusive eruptions are characterized by the gentle, steady flow of lava, as opposed to the explosive eruptions associated with more viscous magmas, and are the dominant eruption style for shield volcanoes.

Hotspot: A hotspot is a fixed, stationary source of magma in the Earth's mantle that can create a series of shield volcanoes as the Earth's crust moves over it, such as the Hawaiian Islands.