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Different Types of Rocks. 6 th Grade . How do Rocks form? . Igneous Rocks : forms from the cooling of magma or lava Sedimentary Rocks : forms when particles of other rocks or the remains of plants and animals are pressed and cemented together
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Different Types of Rocks 6th Grade
How do Rocks form? • Igneous Rocks: forms from the cooling of magma or lava • Sedimentary Rocks: forms when particles of other rocks or the remains of plants and animals are pressed and cemented together • Metamorphic Rocks: forms when an existing rock is changed by heat, pressure or chemical reactions
How can one classify rocks? • By its texture: the look and feel of the rock’s surface • Grains: particles of minerals or other rocks • Give a rock its texture
To describe a rock’s texture, geologists use terms based on the size, shape, and pattern of the grains
Grain Size • 1) Fine Grain: grains are so small that they can only be seen with a microscope
Grain Size - 2) Coarse grain: grains in a rock are large and easy to see
Grain Shape • Rounded Grain: (Conglomerate) • Jagged Grain: (Breccia)
Grain Pattern • Non-banded: • No patterns or bands noticeable • Banded: (foliated) • Grains lie in bands of different colors
Igneous Rocks: “Igneous” comes from Latin word “ignis” which means “Fire” • 1) Extrusive rock = igneous rock formed from lava that erupted onto Earth’s surface • 2) Intrusive rock = igneous rock that is formed when magma is hardened beneath the Earth’s surface
Types of Igneous Rocks • Extrusive Rocks have a fine-grained or glassy texture • Intrusive Rocks have larger crystals in them because they cool more slowly
Sedimentary Rocks • What is sediment? • Small, solid pieces of material that come from rocks or living things – ex. Sand grains, mud, pebbles AND shells, bones, leaves, stems, remains of living things
Sedimentary Rocks: formed from erosion, deposition, compaction, cementation • Erosion: running water, wind, or ice loosen and carry away fragments of rock. • Deposition: the process by which sediment settles out of the water or wind carrying it • Compaction: the process that presses sediments together • Cementation: the process in which dissolved minerals crystallize and glue particles of sediment together
Types of Sedimentary Rocks • Clastic Rock: a sedimentary rock formed when rock fragments are squeezed together • Organic Rock: a sedimentary rock formed when the remains of plants and animals are deposited in thick layers
Metamorphic Rocks: “meta” = change and “morphosis” = form • Rocks that are changed by heat and pressure deep beneath the Earth’s surface • Metamorphic rocks can form out of igneous, sedimentary, or other metamorphic rock • Collisions between Earth’s plates can push the rock down toward the heat of the mantle
Metamorphic Rocks • Foliated: have their grains arranged in parallel layers or bands • Nonfoliated: mineral grains in these rocks are arranged randomly
Granite turns into Gneiss • Shale turns into Slate • Limestone turns into Marble