Rocks Chapter 4-1 The Rock Cycle

Rock – mixture of minerals, glass or organic matter. Granite: igneous rock Mica Plagioclase Orthoclase Horneblend quartz

Rock Cycle Older rocks are recycled to make younger rocks. Various processes that alter the rocks; Melting Temperature and pressure Weathering, erosion and deposition

Three basic rock groups are formed: Igneous – melting and cooling Sedimentary – weathering, erosion and deposition Cementing and compacting Metamorphic – temperature and pressure

Igneous Rocks Formed from molten material in earth’s crust that emerges or remains in earth’s crust. Magma – liquid rock UNDER crust Lava – liquid rock ON crust

Causes of extreme heat in Earth Pressure Heat from earth’s interior Radioactive elements

Two kinds of igneous rocks Intrusive igneous rocks – Cooled slowly Texture – coarse grained - time for large crystal growth Found in surface of earth after weathering

Pegmatite Extremely large crystals Long time for crystal growth Intrusive sites

Gabbro Plagioclase feldspar Pyroxene

Diorite Salt and pepper rock Granite Hornblende – black White Plagioclase – white/gray

Extrusive Igneous Rocks Cools near earth’s surface Cools quickly Texture – fine grained

Rhyolite Feldspar Quartz Biotite mica Fine texture

Basalt Iron rich Pyroxene Plagioclase Olivine Fine texture Quick cooled

Obsidian Volcanic glass Texture – glassy SiO 2 Conchoidal fracture

Pumice Frothy or Glassy threads Silica based Gases emitted from lava at explosion cause strings that make threads So light it floats on water

Scoria Large holes made by gas escaping from lava Volcanic cinders Lava rock Basaltic – darker than pumice

Classification of Igneous Rocks

Igneous rock classified by composition Basalt – dense, heavy, dark colored - rich in Fe and Mg - lava quick moving - ocean bottoms Granitic – light colored, lower density - magma thick contains Si and O 2 - continental plates - contains great deal of gases (explosive) Andesite Andesite – between basalt and granite - violent eruptions

Igneous rocks can be classified by; Composition Basalt – ferromagnesium – Fe and Mg Granite – potassium and silicates SiO 2 Texture: Large crystals Small/no crystals Place of cooling: Intrusive extrusive

Textbook page 92 answer in notebook Self Check 1,2, 3, 4, Applying skills