Hotspots

• Hotspot


  A small area of the earth's crust where an unusually high heat flow is associated with volcanic activity
• Of the 125 hotspots thought to have been active over the last 10 million years most are located well away from plate boundaries
• Hotspot


  • An area of the earth that exists over a mantle plume
  • A mantle plume is an area under the crust, where magma is hotter than the surrounding magma
• Hawaiian hotspot


  The Hawaiian chain of islands lies at the centre of the Pacific plate, thousands of km from the nearest plate boundary. Its formation is due to the existence of a hotspot.
• How Hawaiian hotspot formed

  1. As the Pacific plate has slowly moved northwest over the Hawaiian hotspot (at an average rate of 10cm/year) vast amounts of basalt have accumulated on the ocean floor to produce the Hawaiian Islands

  2. Over millions of years, as the Pacific plate moves northwest and away from the hotspot the volcanoes lose their source of magma and become extinct

  3. On the older islands in the Hawaiian chain, such as Kauai, volcanism is no longer active and weathering and erosion have broken down volcanic rock into deep, fertile soils and spectacular valleys have been carved out by rivers

  4. Further along the chain to the northwest, the volcanic islands have sunk below the surface of the Pacific to form underwater mountains
• Hawaiian Islands


  • Kauai - 5.1 million years old
  • Oahu - 2.2-3.4 million years old
  • Molokai - 1.3-1.9 million years old
  • Maui - 2.32 million years old
  • Hawaii - 0-400,000 years old
• Submarine islands


  Loihi - Located 30km southeast of the big island, currently the summit is 970m below sea level, estimated that the summit will reach the surface in 10,000-100,000 years' time