by Steve Mattox
Lesson at a glance: Mantle plumes are areas of hot, upwelling mantle. A hot spot develops above the plume. Magma generated by the hot spot rises through the rigid plates on the lithosphere and produces active volcanoes at the Earth's surface. As oceanic volcanoes move away from the hot spot, they cool and subside, producing older islands, atolls, and seamounts. As continental volcanoes move away from the hot spot, they cool, subside, and become extinct.

Key Concepts: Hot spots are places within the mantle where rocks melt to generate magma. The presence of a hot spot is inferred by anomalous volcanism, such as the Hawaiian volcanoes within the Pacific Plate. The Hawaiian hot spot has been active at least 70 million years, producing a volcanic chain that extends 3,750 miles (6,000 km) across the northwest Pacific Ocean. Hot spots also develop beneath continents. The Yellowstone hot spot has been active at least 15 million years, producing a chain of calderas and volcanic features along the Snake River Plain that extends 400 miles (650 km) westward from northwest Wyoming to the Idaho-Oregon border.

Lesson Outcomes: The students will:

  1. gain perspective on how new ideas develop in geological sciences
  2. relate mantle plumes and hot spots to plate tectonics
  3. explain why the Hawaiian Islands become progressively older to the northwest

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