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EnglandGeologyQuick questions
Rock-forming processes
Quick questions on Igneous intrusions and volcanic forms: sills, dykes, batholiths, chilled and baked margins, cross-cutting and volcanic landforms - Eduqas A-Level Geology
6short 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 intrusive forms?Show answer
Magma that solidifies underground forms intrusive (plutonic) bodies, classified by shape and by their relationship to the bedding of the surrounding country rock:
What are cross-cutting relationships?Show answer
Because an igneous body must intrude rock that already exists, any intrusion that cuts another rock is younger than it (the principle of cross-cutting relationships). A dyke cutting a sill is younger than the sill. Combined with the chilled and baked-margin logic, this lets you order a whole cross-section.
What are volcanic forms?Show answer
Magma that reaches the surface builds volcanic landforms, whose shape depends on the magma's composition and the eruption style:
What is q1?Show answer
State whether a sill is concordant or discordant, and explain why. [2 marks]
What is q2?Show answer
Explain how a baked margin can be used to show that an intrusion is younger than the country rock. [2 marks]
What is q3?Show answer
Name the volcanic form built by runny basaltic lava and the form built by viscous, explosive andesitic eruptions. [2 marks]
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