Classifying Rocks What is a rock Rocks are

Classifying Rocks

What is a rock? • Rocks are naturally occurring solid mixtures of one or more minerals or organic matter.

Rocks • A. Classifying Rocks • 1. Composition – Minerals they are made from • A. Some rocks contain only one mineral • B. Most rocks contain more than one mineral • i. 20 minerals form most of the rocks that make up the earth’s crust

Texture • 2. Texture- look and feel of a rocks surface • Grain – particles made of minerals or other rocks • A. Grain Size • 1. Fine Grain – small grain • 2. Coarse Grain – large grains • 3. no visible grains • B. Grain Shape • 1. Rounded Grain • 2. Jagged Grain • C. Grain Pattern • 1. Banded grain • 2. Non-banded grain

Types • A. Igneous Rocks- cooling of magma or lava • B. Sedimentary Rocks – particles of other rock or remains of plants and animals are pressed and cemented together • C. Metamorphic Rocks- existing rocks are changed by heat, pressure or chemical reactions

Igneous Rocks

Igneous Rocks • A. types by Texture- size of grains or crystals • 1. Extrusive Rock- magma or lava that cools and hardens at or near the earth’s surface • a. rock cools very quickly • b. crystals are small, if any at all • c. Examples: basalt, obsidian, pumice, rhyolite

Igneous Rocks • 2. Intrusive Rock- magma that cools and hardens within the earth • a. rock cools very slow • b. crystals are very large • c. examples: granite, gabbro, diorite

Igneous Rocks • Types by composition- amount of silica • 1. high silica content – light colored • a. Examples: Granite, rhyolite • 2. low silica content – dark colored • a. Examples: gabbro, basalt

Igneous rocks • Uses of Igneous Rocks • 1. Granite- statutes, headstones, bridges, buildings, floors, kitchen counters • 2. Pumice, abrasives for cleaning and polishing • 3. Obsidian- ancient tools

Igneous Video • http: //www. videojug. com/film/geology-igneous-rocks

Sedimentary Rocks

Sedimentary Rocks • A. Process to form a sedimentary rock • 1. weathering and erosion • weathering- wind and water breaking rocks into smaller pieces • Erosion- wind and water carrying away particles

Sedimentary Rocks • 2. Deposition- sediments settling out of the wind or water

Sedimentary Rocks • 3. Compaction- process of pressing the sediments together

Sedimentary Rocks • 4. Cementation- dissolved minerals crystalize and glue particles of sediment together

Types of Sedimentary Rocks • 1. Clastic Rocks-rocks made from pieces of other rock • • a. shale – made of clay b. sandstone – made from sand c. conglomerate – mixture of different sized rounded particles d. breccia- mixture of different sized jagged particles

Types of sedimentary rocks • 2. Organic Rocks – made from the remains of plants and animals • a. coal – made from plants • b. limestone – made from coral, clams and oyster shells

Types of Sedimentary rocks • 3. Chemical rocks – rocks made when minerals in a solution crystalize • a. limestone – made from calcite dissolved in lakes, seas or underground water • b. rock salt – made from evaporated oceans and seas

USES of sedimentary rocks • Sandstone – buildings • Limestone – buildings • Flint - Arrowheads

Process of Deposition • Process in which material is laid down

Weathering, Erosion and Deposition • All geological processes that make and destroy rock

Strata • Strata = Layers • Stratification- process in which sedimentary rocks are arranged in layers

Organic materials… • Sedimentary rocks are the only rocks with fossils

Metamorphic Rocks

Metamorphic Rocks • Metamorphic Rocks- existing rocks are changed by heat and pressure • Meta- change • Morphism - forms

Types of Metamorphic rocks • Foliated Rocks- when minerals flatten out and line up in bands or parallel layers due to pressure • a. gneiss forms from granite • b. slate forms from shale

Types of Metamorphic Rocks • 2. Nonfoliated Rocks- rocks that do not show bands Not enough pressure on the rock to form bands a. marble forms from limestone b. quartzite forms from sandstone

USES of metamorphic rocks • 1. Marble: buildings, statues, countertop • 2. Slate: flooring, roofing, chalkboards, pool tables

Metamorphic video • http: //www. youtube. com/watch? v=Urim. Db. TUalg&feature =relmfu&safety_mode=true&persist_safety_mode=1