What Are Igneous Rocks What is the difference

What Are Igneous Rocks?

What is the difference between a mineral and a rock? u Minerals: – Naturally occurring – Inorganic – Solid – Chemical composition – Definite crystalline structure u Rocks: Made up of minerals

The Rock Cycle Interaction among Earth’s water, air, land living things can cause rocks to change from one type to another. u The rock cycle is a continuous process u

What Are Igneous Rocks u Rocks that form when magma or lava cools, crystallizes, and hardens above or beneath the surface.

LAVA vs. MAGMA Lava u When magma reaches the Earth’s surface Magma u Liquid rock below the Earth’s surface

Formation of Igneous Rocks Extrusive Igneous Rocks u u Rocks that form by cooling rapidly on Earth’s surface, usually from an erupting volcano. These rocks are finegrained. EX: Obsidian Intrusive Igneous Rocks u Rocks that are coarsegrained igneous rocks that cool slowly beneath Earth’s surface. u EX: Granite

Rock Texture deals with how big the crystals are in an igneous rock. – Coarse-Grained: Large crystals, slow cooling – Fine-Grained: Small crystals, fast cooling – Glassy: No crystals, instant cooling – Porphyritic: Both large and small crystals, slow cooling with different minerals

Coarse-grained Fine Grained Glassy Porphyritic

Rock Composition u u The composition deals with the chemical makeup of the rock. “ What minerals are inside the rock? ” – Felsic (light) – Andesitic (medium) – Mafic (dark) – Ultramafic (very dark)

Composition Felsic (Granitic) u Almost entirely of light-colored silicate minerals. Usually with quartz – Ex: Granite Mafic (Basaltic) u Many dark silicate minerals u Rich in magnesium and iron u Ex: basalt and gabbro

Composition Andesitic u Composition between felsic and mafic u Rock that is half dark, half light Ultramafic u Composed mainly of iron and magnesium-rich minerals u Almost entirely dark minerals

Smile! Igneous Rocks are Not that hard!