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| The Earth's Building Blocks. ROCKS AND MINERALS. |
You might think that rocks are fairly dull. However
rocks tell the history of the Earth, together with stories of large explosions,
mountains rising from the ocean, and buried forests turning to stone.
Rocks are created of one or more minerals. Most
minerals are inorganic, which implies that they're not made up of living
things. They're substances that occur naturally within the earth. Some minerals
are metals, like iron and gold. Others are Metallica, like quartz and calcite.
Some minerals contain the hardened remains of animals
and plants. Limestone rock, for example, is formed up largely of bits and items
of shells and skeletons of ocean creatures.
All rocks comprise one among three groups, depending
on how they are formed. Igneous rocks are formed from cooling magma, which is
the lava released in a eruption. The earliest rocks were igneous.
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| The Earth's Building Blocks. ROCKS AND MINERALS. |
Rocks don't stay the same forever. They break down
into small pieces because of the of wind, water, and ice. When little pieces of
rock settle together, they're referred to as 'sediment'. As layers of sediment
settle on top of each other over many years, their weight squeezes the pieces
together into solid sedimentary rock. This photo shows the very common
sedimentary rock called 'sandstone', which is cemented sand.
The third group of rocks gets its name from the word 'metamorphosis', which implies 'change'. Metamorphic rocks are created once
extreme temperatures or pressures cause changes in igneous or substance rocks.
Marble is a metamorphic rock made from intensely squeezed and heated
sedimentary rock. And limestone, you will keep in mind, began as seashells and
skeletons. This is another superb Earth story told by a rock!
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| The Earth's Building Blocks. ROCKS AND MINERALS. |
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