The Origin of Rocks (background)

Generally, rocks are formed by one of three processes. They are classified into the following categories:

Igneous

Igneous rocks are made from magma that rises toward the Earth’s surface and either stays underground (and is exposed later through weathering) or erupts from volcanoes.

igneous

Ignis is Latin for "fire."

We turn on the ignition in the car.

Metamorphic

Under extremely strong forces igneous and/or sedimentary rocks can be reshaped into metamorphic rocks. Rocks change under pressure, becoming more compact. They are significantly pressured in a side-to-side direction.

Crystals and fossils in the rocks can be stretched and distorted by this pressure. Rocks can also be changed by heating, for example, when they are pressed against hot magma. In addition, they can be changed by chemical activity. Water can dissolve minerals and then crystallize them within a rock.

metamorphic

Meta is Greek for

"change."

Morphos is Greek for "shape."

To "metamorphose" means to change shape.

Sedimentary

Most surface rock is sedimentary (66%), so you might expect to find some sedimentary rock near you. There are three kinds of sedimentary rock, depending on the source of the sediment.

Sediment comes from:

- the weathering of mountains;

- the compressed remains of organisms (limestone, for example, is made from shells and coal is made from compressed vegetable matter); or

- chemical processes that decompose rock.

sedimentary

Sedere is Latin for "to sit." Some people have sedentary lifestyles.

You might want to ask:

IF sedimentary - How did it get laid down? Water? Weathering? Both?

IF igneous –Was the magma intrusion or volcanic

IF metamorphic - How does the earlier-made rock get changed? By heating, collisions, deep burial and pressure? All?