A shield volcano is a broad, gently sloping landform created by the eruption of low-viscosity basalt lava that can flow over long distances. These volcanoes are characterized by their dome-like shape and are primarily formed from repeated, non-explosive eruptions, making them different from steeper stratovolcanoes. The low viscosity of the lava allows it to spread out and create the shield-like profile, which is commonly seen in volcanic regions such as Hawaii.
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Shield volcanoes typically have low-profile shapes, with slopes averaging around 3 to 10 degrees.
The eruptions from shield volcanoes are generally non-explosive, producing large volumes of basalt lava that flows out in a manner similar to a fountain.
Over time, shield volcanoes can become massive structures, with some reaching heights of over 10,000 feet above sea level.
The Hawaiian Islands are primarily composed of shield volcanoes, which have formed over millions of years as the Pacific Plate moves over a hotspot.
Unlike stratovolcanoes, which can be more dangerous due to explosive eruptions, shield volcanoes pose less risk to nearby populations during eruptions.
Review Questions
What are the key characteristics that distinguish shield volcanoes from other types of volcanoes?
Shield volcanoes are distinguished by their broad, gently sloping profiles and non-explosive eruptions. They are primarily composed of low-viscosity basalt lava that can flow over great distances, forming their characteristic shape. Unlike stratovolcanoes, which have steeper slopes and often produce more explosive eruptions, shield volcanoes result from continuous and consistent lava flows that create wide bases.
Discuss how the formation of shield volcanoes impacts the surrounding geography and ecology.
The formation of shield volcanoes significantly shapes the surrounding geography by creating extensive lava fields and altering landforms over time. As lava flows cool and solidify, they contribute to soil development and can create new habitats for various plant and animal species. The gentle slopes of shield volcanoes also influence weather patterns and water drainage in the area, leading to unique ecological niches that support diverse ecosystems.
Evaluate the role of shield volcanoes in volcanic activity and their implications for human settlements in nearby areas.
Shield volcanoes play a critical role in volcanic activity due to their frequent but typically non-explosive eruptions. While they pose less immediate danger compared to stratovolcanoes, they can still significantly impact human settlements through lava flows that can destroy infrastructure and property. Understanding the behavior of shield volcanoes is essential for developing effective hazard assessments and preparedness plans for communities living near these geological features.
One of the largest shield volcanoes in the world located in Hawaii, which exemplifies the characteristics of shield volcanoes with its gentle slopes and extensive lava flows.
Volcanic island arc: A chain of volcanic islands formed at convergent plate boundaries where an oceanic plate subducts beneath another oceanic plate, often featuring both shield and stratovolcanoes.