USA Volcano Hotspots Quiz
Hawaii, Alaska/Aleutians, Cascades; why these areas erupt (10 questions).
USA Volcano Hotspots Quiz: Quick Study Notes
The United States is home to diverse and dynamic volcanic landscapes, primarily concentrated in three major regions: Hawaii, Alaska/Aleutian Islands, and the Pacific Northwest’s Cascade Range. These areas exhibit distinct volcanic styles and origins, offering a fascinating glimpse into Earth’s powerful internal processes, from deep mantle plumes to active subduction zones.
Key Regions & Mechanisms
Formed by a stationary mantle plume, creating a chain of shield volcanoes as the Pacific Plate moves overhead. Characterized by effusive, basaltic eruptions.
The Aleutian Arc is a classic example of an island arc formed by the subduction of the Pacific Plate beneath the North American Plate, leading to explosive stratovolcanoes.
The Cascade Range in the contiguous U.S. results from the subduction of the Juan de Fuca Plate beneath the North American Plate, creating a line of iconic, potentially explosive stratovolcanoes.
Volcanoes erupt due to either magma rising from deep mantle plumes (hotspots) or the melting of the mantle wedge above a subducting oceanic plate, often facilitated by water-induced flux melting.
Key Takeaways
- Hawaii’s volcanism is driven by a deep, stationary mantle hotspot, forming shield volcanoes.
- The Aleutian Islands are an island arc formed by oceanic-oceanic subduction, producing explosive stratovolcanoes.
- The Cascade Range is a continental arc formed by oceanic-continental subduction, also featuring explosive stratovolcanoes.
- Subduction zones cause volcanism when water released from the subducting plate lowers the melting point of the overlying mantle.
- Hotspots involve magma plumes rising from deep within the Earth’s mantle, independent of plate boundaries.
- The U.S. volcanic regions showcase both effusive (Hawaii) and explosive (Alaska, Cascades) eruption styles.
Frequently Asked Questions
Q: Why does Hawaii have volcanoes despite not being on a plate boundary?
A: Hawaii’s volcanoes are formed by a “hotspot” – a deep, stationary mantle plume that punches through the Pacific Plate as it moves overhead, creating a chain of islands.
Q: What is the primary difference between Hawaiian and Cascade volcanoes?
A: Hawaiian volcanoes (shield volcanoes) are formed by a hotspot, producing effusive basaltic lava flows. Cascade volcanoes (stratovolcanoes) are formed by subduction, leading to more viscous magma and potentially explosive eruptions.
Q: Which tectonic plates are involved in the volcanism of the Aleutian Islands?
A: The Aleutian Islands’ volcanism results from the subduction of the Pacific Plate beneath the North American Plate, creating an island arc.
Q: What makes subduction zone volcanoes, like those in the Cascades, so explosive?
A: Magma in subduction zones tends to be more viscous and gas-rich due to the incorporation of water and other volatiles from the subducting plate. This trapped gas leads to immense pressure buildup and explosive eruptions.
Q: Are all volcanic hotspots located in the middle of oceanic plates?
A: While many prominent hotspots like Hawaii are oceanic, some continental hotspots also exist, such as Yellowstone, which is responsible for supervolcano activity.
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