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
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.
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