Metamorphic Rocks

Metamorphic rocks form when already existing rock (can be igneous, sedimentary or metamorphic) is put under pressure (squeezed) and heated underground. This can cause folds to form in the rock. Folds are when the rock has been bent and heated - so you will see the different minerals and layers are curved or bent.

When a rock is heated and put under pressure it changes into a metamorphic rock.

Follow the video and add the pictures and facts below to your rock cycle worksheet.

thumbnail_Website Graphics - metamorphic@2x.png

Describe a Metamorphic Rock

There are lots of different types of metamorphic rock, and what they look like depends on what rock has been changed and how much heat and pressure has changed it.

Explore some of the metamorphic rocks in the GeoBus collection below. Move your mouse over the top of the first image to find out more about that rock.

Marble

You can get lots of different types and colours of marble, but the marble in our collection is white with medium sized crystals. The crystals reflect light so that it looks glittery. Limestone changes into marble when put under intense pressure and heat.

Gneiss

This rock has a very strange name that is difficult to say! The correct way to pronounce is without the G and sounds like ‘nice’. Gneiss is one of the oldest type of rocks you can find on Earth. The Gneiss in our collection is grey and shiny, with some pink and black crystals. It is quite hard to see, but this example shows banding - stripes of either black, grey or pink minerals.

Schist

Another difficult to pronounce rock name! Try it it without the C, sounds like ‘shist’. This piece of schist is one of our favourite rocks in the collection because it is made up of large dark purple crystals of garnet. It is grey and shiny, and also a favourite amongst students.

Famous Rocks: Highlands, Scotland

A metamorphic rock called quartzite from Northern Scotland near the Moine Thrust.

Quartzite with Skolithos burrows, UK by Sara Carena on Sketchfab

Proceed to Part 5: The Rock Cycle