Igneous Rocks How do we classify igneous rocks

Igneous Rocks How do we classify igneous rocks?

Igneous Rocks ² Igneous Rocks – rock type that forms when molten material solidifies ² Methods to classify igneous rocks:

Igneous Rocks Environment of Formation ² Environment of Formation – the location where liquid rock solidifies into solid rock

Igneous Rocks Environment of Formation ² Magma – molten rock that is inside of the Earth ² Plutonic – rock that formed deep within the Earth ² Intrusive – below Earth’s crust

Environment of Formation

Igneous Rocks Environment of Formation ² Lava – molten rock that is outside of the Earth ² Volcanic – rock that formed on the Earth’s surface ² Extrusive – above Earth’s crust

Environment of Formation

Igneous Rocks Color ² Color – for igneous rocks color is broken into two categories of light and dark Dark Light

Igneous Rocks Composition ² Composition – a mixture of materials that make up an igneous rock

Igneous Rocks Composition ² Felsic – light colored rocks that have a high aluminum (Al) and silicon (Si) content Granite Rhyolite

Igneous Rocks Composition ² Mafic – dark colored rocks that have a high iron (Fe) or magnesium (Mg) content Basalt Scoria

Igneous Rocks Texture ² Texture – the appearance or character of a rock ²Vesicular – texture that consists of gas pockets that give the appearance of having holes ²Porphyritic – texture that contains large crystals in a fine grained matrix

Igneous Rocks Vesicular Porphyritic

Igneous Rocks Grain Size/Crystal Size Grain Size – refers to the actual measurement of the individual grains or aggregate Obsidian Granite

Igneous Rocks Grain Size/Crystal Size ² Grain size is an important factor to determine the environment of formation ²The longer the cooling time the larger the grain size (coarse grained) ²The shorter the cooling time the smaller the grain size (fine grained)

Igneous Rocks Coarse Grained Large Crystals Long Cooling Fine Grained Small Crystals Short Cooling

ESRT p. 6