Magma Plumes (AQA AS Geography): Revision Note

Hot Spots

• Hot spots form around the core of the Earth where radioactive decay is concentrated

• This extreme heat creates magma plumes

  • These are upwellings of superheated rock that rise from deep within the Earth’s mantle towards the surface

  • They can break through the middle of a tectonic plate to reach the surface causing volcanic activity and earthquakes far away from plate margins

• Magma plumes (often referred to as hotspots) are the primary mechanism for intraplate tectonic activity—meaning volcanic activity that occurs in the middle of a tectonic plate rather than at its edges

  • Examples include:

    • New Madrid Seismic Zone (USA): a major fault zone in the central US

    • 2011 Christchurch earthquake, NZ

    • Hawaiian hotspots

Key Characteristics and Causes

• Location: Occur in the middle of plates, not at boundaries

• Mechanisms: Driven by stress concentration, mantle plumes, glacial-isostatic adjustment, or ridge push

• Seismicity: Often linked to ancient faults or failed rifts (e.g., in North America)

• Volcanism: Mid-plate hotspots, like Hawaii, are examples of intraplate volcanic activity

• Hazards: Because these areas are often not designed for earthquakes, they can cause significant damage

Island Chains

• Hot spots and magma plumes can lead to the creation of island chains such as Hawaii

• The magma plume is stationary so when the tectonic plate moves over it, a chain of volcanoes is formed

• The volcanoes are active when they are above the magma plume, but become extinct as the plate moves away

• The oldest island is the one furthest away from the plume