Spark image

Structure of the Earth

Rock types

Igneous

These rocks are volcanic in origin Random interlocking of crystals of different materials during the cooling.
Intrusive: Slow cooling (within the Earth's crust) gives large crystals which are easy to seen granite
Extrusive: Rapid cooling (from volcanoes) small crystals which can be seen under a microscope (extrusive rock) basalt. Pumice gas trapped in the rock during solidification low density.
Igneous rocks are - Hard, have no fossils, have an interlocking crystal structure

Sedimentary

This type of rock is deposited as fine particles from ancient seas. Layers.
The rocks are then formed by compression to give various types such as chalk, limestone, sandstone and mudstone.
Rocks made of large sized particles (pebbles) are called conglomerates (sometimes called "pudding stone" because it looks a bit like a pudding).
Inorganic formed from particles or fragments of rock
Organic formed from shells and skeletons of tiny organisms.

Metamorphic

These rocks are ones that have been changed during their lifetime. These changes occurred because of the action of heat and pressure on the rocks.
Heat only:
Limestone changes to marble
Heat and pressure:
Mudstone (clay) changes to slate and schist. Slate can be split into sheets (cleaved). This makes it very useful for roofing and is caused by the effects of pressure during formation.

Greek: meta change morphe - shape



 
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