The document discusses the three main types of rocks: igneous, metamorphic, and sedimentary rocks. Igneous rocks form from cooling magma either underground as intrusive igneous rocks or above ground as extrusive igneous rocks. Metamorphic rocks form from existing rocks being subjected to heat and pressure, altering their mineral composition. Sedimentary rocks form through the compaction and cementation of sediments over millions of years.

1. The Rock Cycle
By Robyn Leslie

2. Igneous Rocks
How are they formed?
Extrusive Igneous rocks, or volcanics, form when magma
makes its way to the Earth’s surface. The molten rock
erupts or flows above the surface as lava and then
cools forming rock. The lava comes from the upper
mantle layer between 50km and 150km below the Earth’s
surface.
Below the Earth’s, molten rock called Magma flows into
the cracks or underground chambers. There magma sits,
cooling very slowly over thousands to millions of
years. As it cools elements combine to form common
silicate materials, the building blocks of Igneous
Rocks. These mineral crystals can grow quite large if
space allows. Rocks that form this way are called
intrusive igneous or plutonic rocks.

3. Igneous Rocks
Properties:
- They contain interlocking crystals which are held together very strongly
and make the rock hard.
- The crystal in the rock have a disorderly arrangement.
- The size of the crystals depends on how quickly the rock solidifies
- They never contain fossils.
Examples:
- Andesite
- Basalt
- Dolerite

4. Metamorphic Rocks
How are they formed?
Earth movements can cause rocks to be deeply
buried or squeezed. As a result, the rocks
are heated and put under great pressure.
They do not melt, but the minerals they
contain are changed chemically, forming
metamorphic rocks. Sometimes, metamorphic
rocks are formed when rocks are close to
some molten magma, and so get heated up.
Remember that metamorphic rocks are not made
from melting rock. (Rocks that do melt form
igneous rocks instead.)

5. Metamorphic Rocks
Properties:
- Often have layers of deposition at different times.
- Often have fossils trapped in them.
- They consist of lots of small grains and are often porous and crumbly.
Examples:
- Slate
- Schist
- Marble

6. Sedimentary Rocks
How are they formed?
A river carries, or transports, pieces of broken rock as it flows
along. When the river reaches a lake or the sea, its load of
transported rocks settles to the bottom. We say that the rocks
are deposited. The deposited rocks build up in layers, called
sediments. This process is called sedimentation. The weight of
the sediments on top squashes the sediments at the bottom. This
is called compaction. The water is squeezed out from between the
pieces of rock and crystals of different salts form.The crystals
form a sort of glue that sticks or cements the pieces of rock
together. This process is called cementation.These processes
eventually make a type of rock called sedimentary rock. It may
take millions of years for sedimentary rocks to form.

7. Sedimentary Rocks
Properties:
- Contain more than one sediments.
- May have an organic origin.
- Form layers called Strata
- May contain fossils.
Examples:
- Flint
- Limestone
- Shale