What are rocks ppt

The Rock Cycle

What are rocks?Rocks are made of grains that fit togetherGrains can be different colours, shapes and sizesRocks with rounded grains more likely to absorb water

- porous

Weathering

Three types of weathering Physical Weathering Biological Weathering Chemical Weathering

Physical weathering

caused by physical change like temperature or effects from the wind.

Biological weathering

animal and plants can wear away rocks

Chemical weathering

rainwater is naturally acidic because of the carbon dioxide from the air dissolves in it. Minerals in rocks may react with rainwater, causing the rocks to be weathered.

Three main types of rocks

Sedimentary Igneous Metamorphic

Sedimentary Rocks

Formation river carries or transports, pieces of broken rock as it

flows along and then settles to the bottom and the rocks are deposited.

The deposited rocks build up in layers, called sediments = sedimentation.

Weight of sediments on the top squash the sediments on the bottom = compaction

Water is squeezed out from between the pieces of rock and crystals of different salts form

The crystals forms a sort of glue that sticks the pieces of rock together = cementation

Examples of sedimentary rocksChalkLimestoneSandstone shale

Igneous Rocks

Inside the earth is very hot – hot enough to melt rocks.

Molten rock forms when rocks melt = magma When the magma cools and solidifies, igneous

rocks are formed

Examples of Igneous Rocks

Basalt Granite Obsidian

Metamorphic rocks

They are formed from other rocks that are changed because of heat or pressure

Earth movements can cause rocks to be deeply buried or squeezed. Therefore they are heated and put under pressure

When metamorphic rocks are formed under pressure, its crystals are arranged in layers

Examples of Metamorphic rocks

Slate is formed from shale Marble is formed from limestone