2Classifying rocks Rocks are made up of two or minerals. About 20 minerals make up most of the earth’s rocks.When studying rocks, geologists observe the mineral composition, color and texture of the rock.This rock containsthree minerals.
3Rock colorA rock’s color can indicate the rock’s mineral composition. Certain minerals are light in color while other minerals are dark in color.Granites are usually lightBasalts are usually dark
5Three Groups of Rocks Igneous – form from the cooling of magma or lava Sedimentary – form when particles of rocks are pressed & cemented togetherMetamorphic – when existing rocks are changed by heat, pressure, or chemical reactions.
7IGNEOUS ROCKS Granite Basalt Most common Intrusive rock Igneous rocks are classified according to their origin, texture, and mineral composition.ORIGIN:Extrusive – formed from lava that has erupted.Intrusive – formed when magma hardens under the earth’s surface.Most commonExtrusive rockBasaltMost commonIntrusive rockGranite
8Extrusive vs. Intrusive Rapid coolingSmall crystal size; fine grainedCan have a glassy textureIntrusiveSlow coolingLarger crystals; coarse grained
10Types of Magma/LavaDifferent compositions of lava or magma determine the types of igneous rocks formed.Magma that contains SILICA will form light colored rocks such as granite.If the magma is low in silica will form dark colored rocks such as basalt.
11Uses of Igneous RockIgneous rock has been used for thousands of years for buildings and statues. Granite is the most widely used igneous rock.
12SEDIMENTARY ROCKSSediments are small bits & pieces of rocks, shells, sand, bones, or parts of plants.This iscalled siltCan you seethe shells?Sediments can be carriedaway by water to bedeposited somewhere else.
13From Sediment to Rock Step 3 Step 4 Steps 1 & 2 Erosion Compaction Particles are carried away by wind or waterParticles are depositedDEPOSITIONCompactionParticles are squeezed together by pressureCementationParticles are glued together as mineral solutions hardenStep 3Step 4Steps 1 & 2
17Three Major Types of Sedimentary Rocks ClasticRock formed by rock fragments that are cemented together; sometimes visible large fragments, sometimes small, fine fragmentsTwo common types are conglomerates, sandstone, brecciasOrganicRocks formed by the remains of plants/animals that are cemented together.Two common types are coal and limestoneChemicalFormed when minerals dissolved in water are crystallized when the water evaporates awayCalcite and Halite can form this way.
18CLASTIC SEDIMENTARY ROCKS This is a breccia.Notice the jaggededges.This is sandstone.The individual fragmentsAre not easily seen.These are conglomeratesThis is shale, splitseasily into thin sheets.
19ORGANIC SEDIMENTARY ROCKS Limestone – forms in the ocean from shells, corals, calcite skeletons being compactedCoquina- a special type of limestoneIn which shells can be easily seenCoal is one of the mostimportant organic rocks.Fossils are found mainlyIn sedimentary rocks.
22Limestone is formed from corals, and other sea animals. These shells and animal remains get crushed and cemented together over time to form limestone.
23Limestone formations These are located in Vietnam. These are called pancake rocks!
24More limestone formations Many cave formations are made of limestone.Here are some hot springs in limestone.
25Chemical Sedimentary Rocks Gypsum and Halite are two of the most common chemical sedimentary rocks.They can also be minerals!They formed by dissolved chemicals crystallizing as water evaporates.For this reason they are sometimes called EVAPORITES.
26This is a chemical form of limestone. It is called TUFA. This is GYPSUM in a cave inNew Mexico. Gypsum isCalcium Sulfate. It is usedIn plaster of paris, drywall,and Cement.This is a chemical form of limestone. It is called TUFA.
27Coral Reefs are responsible for much of the limestone on earth. Coral is an animal much like a sea anenome. They have tentacles and eat plankton. To protect their soft bodies they secrete a hard substance called CALCITE. When they die, these calcite shells remain.
28Ancient Coral Reef vs. Living Coral Reef Great Barrier ReefAustralia
29METAMORPHIC ROCKSHeat & pressure deep in the earth can change any rock into a metamorphic rock. They can form from igneous, sedimentary and other metamorphic rocks.Extremely high temps and pressures deep in the earth can actually change a rocks mineral composition.
30Two Types of Metamorphic Rocks FOLIATEDRocks grains arearranged in parallelbands or layersCommon examples:Slate, gneiss, schistNONFOLIATEDGrains are arrangedrandomly.Common examples:Marble, quartzite