Rocks ♥

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  • Created by: Georgina.
  • Created on: 29-04-08 10:31

Sedimentary Rocks

Summary

Sedimentary rocks are rocks that are formed from deposited rock fragments.

How they are formed?

Sedimentary rocks are formed when eroded fragments of old rocks and dead organisms settle and form into sediments. Over millions of years the rocks compress and settle which squeezes out the water and the rock is formed.

What do they look like?

Sedimentary rocks are different layers of rocks that form a big rock or rocks.

Types of sedimentary rock

Sandstone, limestone, conglomerate, gypsum and shale rock.

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Metamorphic Rocks

Summary

Metamorphic rocks are rocks formed from other rocks changed by heat and pressure.

How are they formed?

Metamorphic rocks are rocks that have changed from sedimentary or igneous rocks into metamorphic rock. They change because the rocks are under tons and tons of pressure so forsters build up which causes them to change.

What do they look like?

Metamorphic rocks ar shiny and hard and can some times be shiner than crystals.

Types of Metamorphic rock

Some types of metamorphic rocks are Gneiss, Schist, Basalt, Salte and Marble.

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Igneous Rocks

Summary

Igneous rocks are rocks formed from molten or melted rock.

How are they formed?

Igneous rocks are only formed when other rocks melt, then cool down, then solidify. Melted or molten rock is called magma. It forms under the surface of the earth and forms the earth's crust. Igneous rocks will almost certainly contain crystals.

What do they look like?

Igneous rocks are randomly arranged crystals, that do not cantain fossils.

Types of Igneous rock

Some types of igneous rock are Granite, Pumice, Obsidian, Scoria and Basalt.

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What are Rocks?

Summary

Rocks are made of tiny grains that fit together.

What do they look like?

Some can be sharp which makes them fit together very easily this is often hard rocks, an example of this is granite.

But some rocks can be made with smooth, round pieces which are more likely to be crumbly rocks, an example of this is sandstone.

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Erosion and Transport

Erosion

If a cliff breaks away because of physical weathering, the rocks may break off and roll down the cliff. When they are rolling down they will often break offother bits of rock and you will end up with a pile of rcks at the bottom.

Transport

The current in rivers and streams can move rocks. Fast flowing rivers can can transport large rocks, but slow rivers or streams transport small rocks or sand. While they are travelling downstream, they will often knock against each other to get smaller rocks.

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Rocks and Weathering

Summary

There are three types of weathering that happens to rocks, they are;

Physical weathering

There arethree types of physical weathering;

Temperature weathering-this is were the when the rocks get hot they expand, but at night the temperature falls, so the rock shrinks, over a period of time the rock cracks.

Freeze-thaw weathering-this is were the rock has a crack in it, it rains, the crack fills up with water, it freezes, but needs more room so the crack gets bigger, over time the crack breaks through and the rock breaks.

Wind, rain and waves-this is were thewind blows grains of sand against the rocks, this wears away the rock. The rain lashes against the rock and break it. Wind can crash against the rock to wear it away

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Rocks and Weathering cont.

Biological weathering

This is were animals and plants wear away the rock. For example, a rabbit can dig a hole hit some rock and make it crack. Plants roots can break the rocks.

Chemical weathering

Rainwater that has carbon dioxide can wear away the rocks, because the acid reacts with the rocks, making it slowly wear away.

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