Facts About Rocks
A rock is a hard substance that makes up the crust (outer layer) of the earth.
The whole surface of the death is covered with rock. Including the ocean floor. In some places there are other things on top of the rock hiding it. This include the sea and the soil which is a mixture of a small pleces of rock and the remains of the plant Nd animals.
There are many types of rocks but they all fall into three main classer igneous sedimentary and metamorphic.
Igneous Rock was the first type to form as the earth's crust took shape.This rock is made of magma the molten material inside the earth. This substance still comes to the surface throught volcanoes Magma that rise in this way is called lava.
Sedimentary Rock is formed by the folding and compressing of sand and clay that have been deposited in streambeds or on ocean floor. Sedimentary rocks sometimes contain contain fossils. Some fragments of rock have been washed out to the sea and has warm other rocks on the shore and sand shellfish have take calcuim salt from the water to bulld their shells and then left on the bottorn after their death. Cool deposits are sedimentary but we're formed on land from rotting wood and other plants salt deposits have often been left by the drying up of inland seas.
Metamorphic Rock was originally igneous or sedimentary but has been changed after it was formed. The most common causes for these changes are heat from nearby magma and pressure from earth movements.
Metamorphic rocks include marbie formed from limestone and greas formed from granite.
Clue History
The rocks found in particular areas are a valuable clue to the history of that area. Igneous rocks which are the oldest type of rocks show that an area has been left fairly undisturbed since the early days of the earth.
Sedimentary rocks show that an area was once under the sea.
Metamorphic rock show that the land have an eventful history.
The science that studies these changes is called geology.
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