What is a Rock?. A rock is a: Naturally formed, Consolidated material, Composed of grains of one or more minerals. Some Rocks. Types of Common Rocks. There are three types of common rocks: Igneous rock Sedimentary rock Metamorphic rock. Igneous Rock.
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What is a Rock? • A rock is a: • Naturally formed, • Consolidated material, • Composed of grains of one or more minerals.
Types of Common Rocks • There are three types of common rocks: • Igneous rock • Sedimentary rock • Metamorphic rock
Igneous Rock • Igneous rocks form from the solidification of magma. • Ex: pumice, obsidian
Identifying Igneous Rocks • Where the igneous rock forms in the crust shapes their composition so igneous rocks are identified by their texture. • Extrusive rocks form at or near the surface and are fine-grained. • Intrusive rocks form below the surface and are coarse-grained.
Igneous Rock Features:Felsic • Felsic rocksare rich in potassium feldspar and quartz and arelight in color. • Example is thegranitefamily of rocks. • Felsic rocksare most common in thecontinents.
Igneous Rock Features: Mafic • Mafic rocksare rich indarkplagioclase feldspar and pyroxene. • Example thegabbrofamily of rocks. • Mafic rocksare more common in theocean basins.
Mafic Igneous Rocks Basalt
IgneousIdentification • Some igneous rocks have holes in them that formed during the cooling of the magma. These types are said to bevesicular.
Structure of Igneous Rocks • Shield and Cinder Cone volcanoes will erupt and create lava flows, and lava plateaus, that form igneous rocks. • When magma does not erupt but instead forces its way up through cracks and faults it produces large masses of intrusive rock called plutons.
Plutons • Plutons are classified according to size: • Sills are slabs of igneous rock parallel to the rocks they intrude; • Dikes are slabs of igneous rock that cut across the rock layers they intrude; • A laccollith forms between two rock layers, bulging up to form a dome; • A batholith is the largest intrusion and they form the core of many mountain ranges. • When a volcano erodes the harder volcanic neck is often left behind.
Devil’s Tower is the result of igneous rock that was underground until all the weaker surrounding rock was eroded