Sedimentary, Igneous, and Metamorphic Rocks

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How do you classify igneous, sedimentary and metamorphic rocks?

There are three major classes of rocks – igneous, sedimentary and metamorphic.

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Credit:https://commons.wikimedia.org/wiki/File:Igneous_rock_eng_text.jpg

The larger particles, such as gravel and sand, settle first. By the time the river reaches the sea, it is usually travelling so slowly that the very fine mud particles begin to settle.

During floods when rivers break their banks, sediments are deposited on flat, open land beside the river. These plains are called floodplains. The water in fast ‑moving rivers, along with the weathered rock it takes with it, can carve out deep valleys in the Earth’s surface.

One of the most spectacular examples of this is the Grand Canyon in Arizona, USA.

In the coldest regions of the Earth, especially at high altitudes, bodies of ice called glaciers slowly make their way down slopes.

Credit: https://commons.wikimedia.org/wiki/File:Verdite_(microcrystalline_fuchsite_metamorphite)_South_Africa.jpg

Check Point

A. Fill in the blanks –

1. Rocks are made up of substances called ………….
2. Rocks that form from the cooling of magma below the Earth’s crust or lava are called ……………. …………
3. Rocks that are formed from the particles of sediments are called……………… rocks.
4. A fast-moving river is likely to carry with it sand, gravel and smaller particles. As it slows down on its path to the sea, the river loses energy and particles are deposited, forming ……………….
5. The process of change in the rocks is called metamorphism and the rocks that are formed by these changes are called ………………. rocks.

B. State True or False –

1. All rocks are formed in the Earth’s atmosphere, which includes the Earth’s crust and the top part of its mantle.
2. Sediments are deposited when weathered rock is moved from one place to another by the wind, running water, the sea or glaciers. That process is called metamorphism.
3. Rocks that form from the cooling of magma below the Earth’s crust or lava are called igneous rocks.
4. The heat and pressure can change the composition and appearance of the minerals in rocks.
5. Deposits of dead plants and animals are also called sediments.

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