Shield volcano

Definition

A shield volcano is a type of volcano characterized by its broad, gently sloping sides and primarily formed by the eruption of low-viscosity basalt lava that can flow over great distances. These volcanoes typically produce non-explosive eruptions, resulting in a shape resembling a warrior's shield lying on the ground. The unique structure and eruption style are closely related to the composition of the lava and the tectonic settings in which they occur.

5 Must Know Facts For Your Next Test

1. Shield volcanoes are typically found at hotspot locations or divergent tectonic plate boundaries, where magma can easily rise to the surface.
2. Mauna Loa in Hawaii is one of the largest shield volcanoes in the world and exemplifies the gentle slopes and vast area associated with this type of volcano.
3. Eruptions from shield volcanoes are characterized by low gas content and fluid lava flows, which allow for long-distance travel across the landscape.
4. The broad shape of shield volcanoes results from repeated eruptions that layer lava flows over time, building up gradually rather than through explosive activity.
5. While shield volcanoes are generally less hazardous than stratovolcanoes, they can still pose risks such as lava flows that may threaten nearby communities.

Review Questions

• How do shield volcanoes differ from stratovolcanoes in terms of their eruption style and structure?
  • Shield volcanoes have broad, gently sloping sides and primarily produce non-explosive eruptions due to their low-viscosity basalt lava. In contrast, stratovolcanoes have steeper profiles and are known for their explosive eruptions caused by more viscous magma that traps gases until they build up pressure. The contrasting shapes and eruption styles highlight the differences in magma composition and the tectonic settings in which these types of volcanoes form.
• Discuss the geological processes that lead to the formation of shield volcanoes, including the role of hotspots and lava flows.
  • Shield volcanoes form primarily at hotspots or divergent plate boundaries where magma can rise through the crust. When magma reaches the surface, it erupts as low-viscosity basalt lava, which can flow over large areas, creating broad, gently sloping structures. The repeated layering of these lava flows contributes to the gradual build-up of the shield shape, emphasizing how geological processes like mantle upwelling and plate tectonics drive their formation.
• Evaluate the potential hazards associated with shield volcanoes and how they compare to other types of volcanoes in terms of risk management.
  • While shield volcanoes tend to produce less explosive eruptions compared to stratovolcanoes, they still pose hazards such as extensive lava flows that can encroach upon populated areas. Effective risk management requires monitoring volcanic activity through geological studies and satellite imagery to predict potential eruptions. Understanding these risks allows communities near shield volcanoes to develop evacuation plans and infrastructure resilient to lava flow impacts, ultimately reducing vulnerability to volcanic hazards.

Related terms

Basalt: A fine-grained volcanic rock that is primarily composed of plagioclase and pyroxene, commonly associated with shield volcano eruptions.

Hotspot: An area in the Earth's mantle where heat causes melting of the crust, often leading to volcanic activity, including the formation of shield volcanoes.

Lava flow: The movement of molten rock (lava) from a volcano during an eruption, which can vary in speed and distance depending on the viscosity of the lava.