2What is a Rock?Rocks are naturally occurring solid material made from one or more minerals.Rocks are classified based on the way they were formed.Three types of Rocks:Igneous – form when hot, liquid rock, or magma, cools and solidifiesSedimentary – formed by particles that have been carried or deposited and then compacted and cemented together.Metamorphic – rocks formed from chemical reactions one rock forms into another kind over long periods of time.
4Igneous RocksIgneous rocks are classified according to their composition and texture.4 basic types of texturesGlassy – black and sharpFine grained – interlocking piecesCoarse grained – consist of interlocking mineral crystalsPorphyritic – made of large crystals scattered on the back of small crystals.
5Igneous Rock Formations Extrusive – rock formed from lavaIntrusive – rock formed when magma forces its way upward into preexisting rocks then hardensMagma – molten material below the earth’s surface.Lava – molten material above the earth’s surface.
9Sedimentary RocksSedimentary rocks are classified according to materials from which they are made.There are three types of sedimentary rocks
10Clastic Sedimentary Rocks Formed form fragments of previously existing rockClassified according to size and shape of the fragmentsExamples:Conglomerate – made of pebbles and pebbles are smooth and roundedSandstone – made of small sand-size grains (very common)Shale – made of particles smaller than sand
11Organic Sedimentary Rocks Formed either directly or indirectly from material that was once livingExamples:Limestone – made primarily of mineral calciteChalk – form of fine-grained limestone composed of microscopic shells, small fragments of shells, and calcite crystalsCoal – made from plants that lived million of years ago.
12Chemical Sedimentary Rocks Formed by chemical means that do not involve living organismsExamplesHalite and Gypsum
15How are Metamorphic Rocks Formed? Formed under tremendous heat, great pressure, and chemical reactionsMetamorphism is changing one type of rock into another as a result of heat pressure and/or chemical reaction.Types of Metamorphic Rock:Foliated – mineral crystals are arranged in parallel layers or bands (ex. Schist, slate, and gneiss)Nonfoliated – rocks are not banded and do not break into layers (ex. Marble and quartizite)
17The rock cycle is the continuous changing of rocks from one kind of rock to another over long periods of time.Matter from the earth’s crust is changed from one form to another, but NONE is ever lost.