Here are some of our latest “Ask-a-Geologist” questions & answers

Q: What is in magma that makes up a rock?

A: Magma is the term used for liquid rock which forms deep below the Earth’s surface. Magma can be composed of many different things such as silicates, alkalis, iron and magnesium. The composition of the magma will determine the type of rocks which it will eventually form.

Q: What rocks are changed by high pressure and high temperature?

A: The change of a rock by high temperature and pressure is called metamorphism. This is the process by which metamorphic rocks are formed. Any rock can be changed by metamorphic processes.

Q: What term for metamorphic rock with banded texture?

A: You may be referring to “foliation” which is the layering within a metamorphic rock. Foliation occurs when there is a strong pressure applied to the rock in one direction, just like when you put your hands flat together and push. When this pressure is applied, certain minerals, like mica and chlorite, grow with their long direction perpendicular to the pressure. This make the rock appear with layering and/or banding.

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