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F2: Surface and Internal Processes
Quick questions on Internal heat and the rock cycle - WJEC A-Level Geology
5short Q&A pairs drawn directly from our worked dot-point answer. For full context and worked exam questions, read the parent dot-point page.
What are mantle convection drives the deep processes?Show answer
Because the deep mantle is hotter than the shallow mantle, hot material expands, becomes less dense and rises, while cooler material sinks, setting up slow convection currents in the solid but ductile mantle. These currents, together with the pull of dense subducting slabs, drive plate motion. Convection therefore powers the internal limb of the rock cycle: it carries crust to depth where it is metamorphosed and partly melted, and it brings hot material up where decompression melting generates magma.
What is hot springs and geothermal power?Show answer
Iceland sits on a constructive margin over a plume, so its steep geothermal gradient brings heat near the surface and is harnessed for geothermal electricity, a direct use of high heat flow. Metamorphic aureoles. A granite intrusion carries heat into the surrounding rock, raising the local gradient and baking a contact metamorphic aureole, the internal heat engine working on a small scale. Decompression melting at ridges. Rising mantle beneath a constructive margin melts as pressure falls, generating basaltic magma, an example of convection feeding the igneous part of the rock cycle.
What is q1?Show answer
Name the two main sources of the Earth's internal heat. [2 marks]
What is q2?Show answer
State an average value for the geothermal gradient in the upper crust. [1 mark]
What is q3?Show answer
Explain why mantle convection can occur even though the mantle is solid. [2 marks]
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