Describe how you can distinguish between intrusive and extrusive igneous rocks?

Crystal size is used to distinguish between intrusive and extrusive igneous rocks. Intrusive rocks such as granite will have coarse crystals whereas extrusive rocks such as basalt will have fine glassy crystals. Extrusive rocks have glassy crystals as this requires rapid cooling under water. Furthermore, intrusive rocks will have baked margins in the country rock at both sides whereas extrusive rocks will have one baked margin in the country rock below only.

SS
Answered by Sian S. Geology tutor

11510 Views

See similar Geology A Level tutors

Related Geology A Level answers

All answers ▸

Explain 2 features of a pluton/surrounding country rock that may influence the width of themetamorphic aureoles


How does magma form?


How do anticline and syncline folds differ?


Define the Principle of Original Horizontality


We're here to help

contact us iconContact ustelephone icon+44 (0) 203 773 6020
Facebook logoInstagram logoLinkedIn logo

© MyTutorWeb Ltd 2013–2025

Terms & Conditions|Privacy Policy
Cookie Preferences