Presentation on theme: "Rocks Are made up of minerals"— Presentation transcript:
1 Rocks Are made up of minerals Ex: Granite > 4 mineralsEssential Minerals: always occur in the rockAccessory minerals: sometimes occur
2 Classify Rocks By How they Form! Igneous- Molten Rock cools and hardensSedimentary – Made from sedimentsMetamorphic – Rocks Changed by heat and pressure
3 High Silica content forms light-colored rocks (FELSIC).
4 While lower (but only by about 25%) Silica content forms darker-colored rocks (MAFIC).
5 THE ROCK CYCLERocks are naturally occurring combinations or coherent aggregates of minerals, fossils or other hard materials. They are classified by the way in which they form. The three rock types are: igneous, sedimentary and metamorphic.All rocks on Earth are locked into a system of cycling and re-cycling known as the ROCK CYCLE. (*)
6 IGNEOUS ROCKSIGNEOUS ROCKS are “born of fire”. In other words, they were once molten and upon cooling, the magma (molten rock) crystallized into solid rock. Igneous rocks may form deep inside the Earth or at the Earth’s surface when a volcano erupts. (*)
7 IGNEOUS ROCKS : intrusive Slow cooling deep beneath the Earth’s surface allows crystals to grow to large size. These crystals are easily visible and distinguish this group of igneous rocks as INTRUSIVE.Large CrystalsBoth large and small crystals = porphyry (some grow before others beginTexture size or arrangement of crystalsTo get Large: Cools below Earth’s surface
8 Igneous - IntrusiveGRANITE is a coarse to medium-grained rock that forms from the cooling of magma deep within the Earth light color - felsicDIORITE is very similar to granite, but is distinguished in the hand specimen by the absence of visible quartz.Generally it has a salt and pepper appearance (about ½ black and ½ white).
9 Igneous RocksRapid cooling near or at the Earth’s surface, produces many small crystals. This group of igneous rocks is called EXTRUSIVEEruption at surfaceNumerous holes at the surfaceSmall mineral crystals ex: basaltNo mineral crystals ex: obsidianTop Part of Lava- gases trapped inside of hardened lava = scoriaFrom lava thrown outex: pumice
10 Igneous - ExtrusiveRhyolite is a fine grained, felsic rock that forms from the cooling of lava above Earth’s surfaceBasalt a dark fine grained rock formed from thin to massive lava flows (mafic)Pahoehoe is a type of basalt that forms on the surface of very fluid lava flows
11 Igneous Review Lava Extrusive Through Volcanoes Through hydrothermal ventsMagma Intrusive/Plutonic- Cools and Crystalizes in Magma Chamber
12 Note: the minerals of igneous rocks are arranged randomly throughout the rock. There are no parallel alignments or fundamental segregations.(*)
13 SEDIMENTARY ROCKSSEDIMENTARY ROCKS are composed of particles derived from pre-existing rocks or by the crystallization of minerals that were held in solutionsWeathering : Rocks are broken into pieces by water, wind or iceWater – enter cracks, expands and breaks rocks downRain – acid rain dissolves mineralsMovement in Rivers – Collect on the bottom
14 Formation – Build very slowly Formation – Build very slowly layers will grow until environment changesCementation – minerals acting as cement holding sediments togetherCompaction – pieces compact due to weight squeezing them togetherPrecipitation – water evaporates and minerals are left behind
15 Unusual FormationChemical Rocks – made up of chemical sediments or once living thingsOrganic Rocks – made up of remains of living things
16 Sedimentary Features Layers Only type of rock that contains Fossils! Ripple Marks – Air or water sand, silt, and clayConcretion – water comes into contact with fossils and mineral depositsGeode – hollow rocks with mineral crystals inside
17 Classifying Clastic Rocks (pieces of other rocks): Conglomerate & Breccias: Large sedimentsSandstones: Small grainsSiltstone : Very Small grainsShale : Very Small grains Clay pressed together
18 Classifying Non-Clastic Rocks (minerals in water or past life): - Look at composition: calcite, halite, gypsum or quartzLimestone - Calcite and seashellsRocks Salt - HaliteRock Gypsum - GypsumChert (flint) - QuartzCoal – Past life
19 METAMORPHIC ROCKSMETAMORPHIC ROCKS have changed (meta) their form (morphic). Under the influence of heat, pressure and fluids, pre-existing rocks are modified in formOriginal rock is called the parent rockThis is done within the solid state, i.e. without melting.3 Types of Changes that occur include:- Change in Chemistry of Rock- Englargement of crystals- Rearrangement of mineral grains
20 ClassifyBurial Metamorphism – weight of overlying rock, causes a reorientation of mineral grainsRegional Metamorphism – As mountains rise, large amount of magma is forced toward the surface , it hardens into the mountain coreContact Metamorphism – Small amount of magma intrudes overlying rockThe nearby Rock is altered by heat, solutions, and gases from the magma*Metamorphism is the MOST intense near the core where heat and pressure cause the formation of new minerals of existing mineral grains
21 FeaturesMetamorphic rocks composed of minerals that are not elongated or flat, do not exhibit parallel alignments and are called NON-FOLIATED.Metamorphic rocks that exhibit parallel alignments of minerals are called FOLIATED. In these rocks, the minerals all line up perpendicular to the exerted pressure.
22 Thinking about relationships among the major rock groups The Rock CycleThinking about relationships among the major rock groups
23 Major Rock Groups Igneous Sedimentary Metamorphic Formed from a melt (molten rock)Plutonic (intrusive):slow cooling and crystallizationVolcanic (extrusion): quick cooling at the surfaceSedimentaryFormed at the Earth’s surfaceClastic (Mineral Fragments or grains, clays)Chemical (crystalline chemical/biochemical precipitates)MetamorphicChanged by pressure, temperature and fluids.
33 Can you see any shortcuts? CompactionSEDIMENTWeatheringCementationEvaporationVolcanicIGNEOUSPlutonicCan you seeany shortcuts?SEDIMENTARYIncreased P&TMETAMORPHICCrystallizationMeltingBurialUpliftMAGMA
35 In Conclusion…The rock cycle demonstrates the relationships among the three major rock groupsIt is powered by the interior heat of the EarthAs well as earth’s momentum and…The energy from the sunIt involves processes on the Earth’s surface as well as the Earth’s interiorIt connects the “hydrologic cycle” with the “tectonic cycle”.