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WalesGeologyQuick questions
G1: Rock Forming Processes
Quick questions on Igneous textures and intrusions - 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 is cooling rate controls crystal size?Show answer
The single most useful idea is that crystal size records cooling rate. Slow cooling gives atoms time to migrate and build large crystals; fast cooling freezes many small crystals; instant quenching gives a glass.
What are contact relationships?Show answer
Contacts tell you whether a rock was intruded or erupted, and its relative age.
What is q1?Show answer
State the cooling history recorded by a porphyritic texture. [2 marks]
What is q2?Show answer
Distinguish a dyke from a sill in terms of their relationship to bedding. [2 marks]
What is q3?Show answer
Explain how a chilled margin and a baked contact establish the relative age of an intrusion. [2 marks]
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