Alevel Geography Hazards: How did Hawaii form?

This is a useful case study for Plate Tectonics in Alevel Geography, especially when considering anomalous geological formations, which do not appear to abide by the regular rules of plate tectonics.

Please note that this resource has been particularly produced with 'Topic Five: Hazards' on the AQA exam board in mind.

Explain, with reference to a named example, how magma plumes form a chain of volcanoes. (12 marks)*

It is well known that most volcanic activity appears at plate margins, particularly around the edge of the Pacific Ocean. The island chain of Hawaii, a volcanic hot spot, is thus quite irregular, in that it is not formed at plate margins, but rather due to a magma plume, in the centre of the Pacific Plate.

A magma plume is a vertical column of extra-hot magma which can rises above the rest of the magma in the asthenosphere, radiating up through the lithosphere to the crust, producing an area of intense volcanic activity at the earth's surface.

This magma plume is simultaneously stationary and continually active, meaning that the process continues over time, that said it does not always affect the same part of the earth's crust, as the plate continues to progressively move over the plume. As the crust moves further from the plume, its surface ceases to be a 'hot spot' as the volcanic activity decreases.

That said, new crust continues to gradually move over the plume. The extra-hot magma continues to rise out of the mantle, forming a bulge under the crust and gradually pushes up through cracks in the crust, to form new volcanoes. The basaltic lava, found in Hawaii, tends to form volcanoes with gently sloping sides. This process continues, forming a chain of volcanoes - as evidenced in Hawaii, where the currently active volcano, Kilauea, which last erupted in 2020, sits on the biggest (and youngest) island.

*Typically this question style would be more representative of a 6 mark question, but to level it up and encourage students to practise applying their case study knowledge I have tweaked it.

Recommended Additional Study Resource: How did Hawaii form by Scientific American, available on YouTube - https://www.youtube.com/watch?v=LdlEufZop-Y