Initial Stage:
* Formation of a "hotspot" volcano: The plume's intense heat melts the overlying lithosphere, creating magma that rises to the surface. This forms a single, often large, volcano called a "hotspot volcano" (e.g., Hawaii's Mauna Loa).
* Volcanic activity is intense and consistent: Because the plume provides a continuous source of magma, the volcano remains active for long periods.
Intermediate Stage:
* Plate movement creates a volcanic chain: As the plate drifts over the stationary plume, the volcano is moved away from the plume's heat source.
* Volcano becomes extinct: The volcano that was initially over the plume becomes inactive as the magma supply is cut off.
* New volcanoes form: As the plate continues to drift, new volcanoes form along the path, creating a chain of volcanoes (e.g., the Hawaiian Islands).
Final Stage:
* Volcanic activity weakens and eventually ceases: Volcanoes further away from the plume have less access to magma and become less active.
* Erosion and weathering dominate: Once extinct, the volcanoes are subject to erosion and weathering, resulting in the formation of islands or seamounts.
Key Points:
* Plate motion is crucial: The movement of the lithosphere plate over a stationary plume is the driving force behind the changes in volcanic activity.
* Volcanic activity patterns reveal plate movement: The age and activity of volcanoes in a chain provide evidence for plate movement direction and speed.
* Mantle plumes are long-lasting: They can remain active for millions of years, resulting in extensive volcanic chains.
Examples:
* Hawaiian Islands: A prime example of a volcanic chain formed by a mantle plume. The oldest islands are in the northwest and are extinct, while the youngest, Hawaii, is still active.
* Emperor Seamounts: An undersea chain of volcanoes northwest of the Hawaiian Islands. They are older and extinct due to plate movement.
Understanding the relationship between volcanic activity and mantle plumes is essential to comprehending plate tectonics and the formation of various geological features.
