Conditions are hostile beneath your feet… 8.5 Metamorphic rocks Conditions are hostile beneath your feet… Just 15 km below the Earth’s surface the temperature is a scorching 400 °C. The pressure at that depth is 4 000 times greater than the surface pressure.

Heat makes rocks change 8.5 Metamorphic rocks Heat makes rocks change In some places, hot magma comes close to the surface. It heats up the rocks around it. Heat makes rocks change.

8.5 Metamorphic rocks Making marble When limestone gets hot, its atoms rearrange themselves in a new pattern. This makes big crystals which interlock tightly. A new rock has formed. Its name is marble. There has not been a chemical change.

8.5 Metamorphic rocks Making slate Mudstone is a mixture of minerals. When new mountains form, high underground pressures squash mudstone. Water is squeezed out of the mudstone. There are chemical reactions between the different minerals in the mudstone. New crystals form and arrange themselves in layers. This is a new rock – slate.

8.5 Metamorphic rocks Metamorphic rocks Marble and slate are metamorphic rocks. Metamorphic rocks form when heat, high pressure, or both, change igneous or sedimentary rocks. The rocks remain solid during the process. They do not get hot enough to melt.

8.5 Metamorphic rocks All igneous and sedimentary rocks can be changed into metamorphic rocks, so there are many different metamorphic rocks. gneiss schist