Rock Types November 21, 2011
Todays Class • Waiting for email on question for Gordon • Term 2: Grade Breakdown • Test 1: 25% • Test 2: 25% • Term Paper: 25% • Quizzes: 10% • Participation 5% • Test 3: 10% MC
Rock Types • A rock is a collection of one or more minerals. Rocks are divided into three major groups.
Igneous Rocks • rocks of molten origin
Intrusive • magma cooled at depth: often forced into cracks or cavities in a molten condition.Generally coarse-grained.eg granite, quartz, feldspar,
Extrusive • lava cooled on the surface after flowing out of cracks or volcanoes as lava. Generally fine-grained.egpummice, obsidian
SEDIMENTARY ROCKS • are composed of the products of mechanical and chemical weathering. Sedimentary rocks are deposited usually in near-horizontal layers by the agents of transportation. eg wind, water, and ice. Burial produces lithification or hardening.
Sedimentary Sources • deserts - aeolian deposits • glacial deposits • rivers - deltas • shallow marine areas (fossils) • deep marine areas • reefs
Types of Sedimentary Rocks • Conglomerate: composed of large rounded fragments embedded in a fine-grained material(easily eroded because made up of tiny particles and layers).b) Sandstone: composed mainly of sand-sized particles, and these are mainly of quartz.
Types of Sedimentary Rocks • Arkose: composed mainly of sand-sized particles of quartz and feldspar, the latter making up more than 25% of the total.d) Shale: composed of fine particles predominantly of clay size.
Types of Sedimentary Rock • Limestone: composed of calcite either • (1) chemically precipitated in water, or (2) accumulated through the collection of organic remains such as shells, or • (3) the result of building up of organic rock through the action of organisms like corals
METAMORPHIC ROCKS • formed by the influence of heat and pressure on other rocks resulting in changes in mineralogy and texture
Types of Metamorphic • Gneiss: has a banded appearance with alternating composition; may be formed by metamorphism of an igneous or sedimentary rockb) Slate: fine-grained and platy; fissile; formed by the metamorphism of shale.
Types of Metamorphic • Schist: rock flaky minerals (eg mica) aligned in a parallel fashion; formed by the metamorphism of shale and slate.d) Quartzite: hard, mainly composed of quartz; formed by the metamorphism of sandstone.e) Marble: a coarse, but even-grained rock formed by the metamorphism of limestone.