Earth and Space Science / Unit 3: Plate Tectonics
3.7 Hot Spots and Evidence for Plate Motion
Notes
A hot spot is a fixed plume of hot mantle rock that melts the plate above, forming volcanoes away from plate boundaries.
- As a plate moves over a hot spot, a chain of volcanoes forms: Hawaiian Islands. The oldest island is farthest from the hot spot.
- GPS measurements confirm motion directly.
- Example: if an island 500 km from the hot spot is 5 million years old, the plate moved 500 km in 5 million years, which is 10 cm/yr ($500 \text{ km} = 5\times10^7$ cm, divided by $5\times10^6$ yr).
Practice
In a hot spot island chain, the oldest volcano is:
Older islands have been carried away.
Hawaii is unusual because it is:
It sits in the Pacific Plate's interior.
An island 300 km from a hot spot is 6 million years old. The plate speed is:
$300 \text{ km} = 3\times10^7$ cm, divided by $6\times10^6$ yr gives 5 cm/yr.
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