rocks

The rocks are constantly being changed into different types in a recycling process.

The Earth's rocks are constantly changing. They have been slowly recycled over millions of years. This is called the rock cycle. Sedimentary rocks form when tiny particles of rock that have been weathered and eroded settle out of slow moving water. Over time, the layers are compressed and glued together. Metamorphic rocks are formed from other rocks, igneous or sedimentary, which are heated and compressed underground. Igneous rocks are formed when molten rock from volcanic activity cools down either underground or on the surface. This slow but continuous cycle of rock formation is happening right now, all over the planet.

The rock cycle

Rocks on Earth do not always stay the same.

Rocks are continually changing due to processes such as weathering, erosion and large earth movements. The rocks are gradually recycled over millions of years, changing between the different rock types.

This recycling of rocks is a process called the rock cycle.

The three rock types are:

• igneous rocks formed from the cooling of molten rock
• sedimentary rocks formed by small rock pieces being transported in rivers and laid down in layers
• metamorphic rocks formed from another rock under heat and pressure