MWJL+5.2

Vocabulary
Extrusive Rock: Igneous rock that forms from lava that is on the surface of the earth. Intrusive Rock: Igneous rock that forms from magma that is hardened beneath the surface of the earth. Porphyritic texture: A kind of texture when giant crystals are scattered right in a background of smaller crystals.

Characteristics of Igneous Rock

 * Origin
 * Extrusive Rock
 * It is igneous rock formed above the earth's surface.
 * Intrusive Rock
 * It is igneous rock formed beneath the earth's surface.
 * Texture
 * The texture of an igneous rock depends on the size and shape of its mineral crystals.
 * Extrusive and Intrusive rocks usually have different textures.
 * Intrusive rocks have larger crystals than extrusive rocks.
 * Some rocks can have two textures.
 * Rocks can have two textures because it cools in two stages.
 * Mineral Composition
 * Magma that is high in silica usually forms rocks that are light colored.
 * Magma that is low in silica usually forms rocks that are dark colored.

Uses of Igneous Rocks

 * Lots of igneous rocks are hard and durable
 * They have used this type of rock for building materials.
 * Ancient Egyptians used granite for statues.
 * Igneous rock such as basalt, pumice, and obsidian also have important uses.
 * Basalt is crushed to make gravel that is used in construction.
 * pumice is a good abrasive for cleaning and polishing.
 * Perlite is often mixed with soil for starting vegetable seeds.

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