Metamorphic rocks are formed from igneous, sedimentary and other metamorphic rocks that have been altered by temperature and/or pressure.
Regional and Contact Metamorphism
Under intense heat and pressure minerals are recrystallised. This can occur because of regional or contact metamorphism. Regional metamorphism occurs where tectonic plates converge, and subjects rocks to intense pressure and heat, causing deformation of the rocks, which may be visible as folds, faults and tilting. In contact metamorphism rocks come into direct contact with magma and lava, subjecting the rocks to very high temperatures.
TASK 33: Create a Venn diagram comparing foliated and non-foliated metamorphic rocks. There is a Venn Diagram attached as a file at the bottom of the page.
Foliated and Non-Foliated Rocks
When minerals are recrystallised under high pressure they can realign in bands, giving the rocks a flaky or ridged appearance. These are classified as metamorphic foliated rocks. Non-foliated metamorphic rocks do not have a flaky or layered appearance, and will typically break off into chunks. See a video demonstration of the formation of foliated and non foliated rocks.
Under increasing heat and/or pressure metamorphic rocks will continue to change (metamorphose) into new metamorphic rocks.
Watch the videos and be prepared to answer the following questions: (ignore the references to other podcasts and text books).
What are the two types of metamorphism? Where would you expect to see regional metamorphism? How are metamorphic rocks classified? How would you tell the difference between a foliated and a non-foliated metamorphic rock?
TASK 34: Answer the following questions:
What are the two types of metamorphism? Where would you expect to see regional metamorphism? How are metamorphic rocks classified? How would you tell the difference between a foliated and a non-foliated rock?
TASK 35: Make your own kitchen metamorphic rocks. Search for other ideas and negotiate an activity with your teacher. Perhaps you could have a class cookie lab.
Next we'll look at recycling rocks...