2 ELEMENTS EIGHT ELEMENTS MAKE UP MOST OF ALL MINERALS ON THE EARTH Elements combine to form MineralsLISTED IN ORDER OF ABUNDANCEOXYGEN (O)SILICON (Si)ALUMINIUM (Al)IRON (Fe)CALCIUM (Ca)POTASSIUM (K)SODIUM (Na)MAGNESIUM (Mg)
4 MINERALS BUILDING BLOCKS FOR ROCKS DEFINITION: naturally occurring, inorganic solids, consisting of specific chemical elements, and a definite atomic arrayCRYSTALLINE STRUCTURE – ‘CRYSTAL’
5 MINERALS MINERALS: TWO CATEGORIES SILICATES – CONTAIN SILICON & OXYGEN MOLECULES (SiO)NON-SILICATES (NO SiO)
6 NON-SILICATE MINERALS Make up 5% of Earth’s crustNative metals: gold, silver, copperCarbonates: calcite (used in cement)Oxides: hematite (iron ores)Sulfides: galena (lead ores)Sulfates: gypsum (used in plaster)
7 SILICATE MINERALS Make up 90-95% of the Earth’s Crust Dominant component of most rocks, include:QUARTZ (SiO2)FELDSPARSMICAS
8 ROCKS AGGREGATIONS OF 2 OR MORE MINERALS THREE CATEGORIES Same or different minerals combine togetherTHREE CATEGORIESIGNEOUSSEDIMENTARYMETAMORPHIC
9 IGNEOUS ROCKSFORMED FROM COOLED, SOLIDIFIED MOLTEN MATERIAL, AT OR BELOW THE SURFACEPLUTONIC – INTRUSIVE: COOLED BELOW SURFACE AT GREAT DEPTHSVOLCANIC – EXTRUSIVE: COOLED AT OR NEAR THE SURFACE THROUGH VOLCANIC ERUPTIONS
10 IDENTIFICATION OF IGNEOUS ROCKS IDENTIFICATION PROCESSES:TEXTURE:Size, shape and manner of growth of individual crystalsMINERAL COMPOSITIONBased on SiO content
11 COMMON IGNEOUS ROCKSGRANITE: PLUTONIC-INTRUSIVE; PHANERITIC TEXTURE; FELSIC MINERAL COMPOSITIONRHYOLITE: VOLCANIC-EXTRUSIVE; APHANETIC TEXTURE; FELSIC MINERAL COMPOSITIONDIORITE: PLUTONIC-INTRUSIVE; PHANERITIC TEXTURE; INTERMEDIATE MINERAL COMPOSITIONANDESITE: VOLCANIC-EXTRUSIVE; APHANETIC TEXTURE; INTERMEDIATE MINERAL COMPOSITIONGABBRO: PLUTONIC-INTRUSIVE; PHANERITIC TEXTURE; MAFIC MINERAL COMPSITIONBASALT: VOLCANIC-EXTRUSIVE; APHANETIC TEXTURE; MAFIC MINERAL COMPOSITION
12 OTHER IGNEOUS ROCKS VOLCANIC GLASS: PYROCLASTIC ROCKS OBSIDIAN: VOLCANIC-EXTRUSIVE; NO CRYSTALS FORM; SILICA-RICH, COOLED INSTANEOUSLYPUMICE: VOLCANIC-EXTRUSIVE; NO CRYSTALS FORM; SILICA-RICH; SOLIDIFIED FROM ‘GASSY’ LAVAPYROCLASTIC ROCKSTUFF: VOLCANIC-EXTRUSIVE; SOLIDIFIED ‘WELDED’ ASH
13 SEDIMENTARY ROCKSWeathering processes break rock into pieces, sediment, ready for transportation deposition burial lithification into new rocks.
14 CLASSIFYING SEDIMENTARY ROCKS THREE SOURCESDetrital (or clastic) sediment is composed of transported solid fragments (or detritus) of pre-existing igneous, sedimentary or metamorphic rocksChemical sediment forms from previously dissolved minerals that either precipitated from solution in water , or were extracted from water by living organismsOrganic sedimentary rock consisting mainly of plant remains
16 SEDIMENTARY PROCESSES LITHIFICATION:As sediment is buried several kilometers beneath the surface, heated from below, pressure from overlying layers and chemically-active water converts the loose sediment into solid sedimentary rockCompaction - volume of a sediment is reduced by application of pressureCementation - sediment grains are bound to each other by materials originally dissolved during chemical weathering of preexisting rockstypical chemicals include silica and calcium carbonate.
17 METAMORPHIC ROCKSMETAMORPHISM : process by which conditions within the Earth alter the mineral content and structure of any rock, igneous, sedimentary or metamorphic, without melting it.Metamorphism occurs when heat and pressure exceed certain levels, destabilizing the minerals in rocks...but not enough to cause melting
19 GEOLOGIC TIME AND DATING Four basic principlesPrinciple of Original HorizontalityBeds of sediment deposited in water formed as horizontal or nearly horizontal layers.Principle of SuperpositionWithin a sequence of undisturbed sedimentary or volcanic rocks, the layers get younger going from bottom to top.Lateral ContinuityAn original sedimentary layer extends laterally until it tapers or thins at its edgesCross-cutting RelationshipsA disrupted pattern is older than the cause of the disruption.
20 DATING - RELATIVE Physical Continuity Similarity of Rock Types Physically tracing the course of a rock unit to correlate rocks between two different placesSimilarity of Rock TypesCorrelation of two regions by assumption that similar rock types in two regions formed at same time, under same circumstancesCorrelation by FossilsPlants and animals that lived at the time rock formed were buried by sedimentfossil remains preserved in the layers of sedimentary rock -fossils nearer the bottom (in older rock) are more unlike -those near the topObservations formalized into Principle of Faunal Succession – fossil species succeed one another in a definite and recognizable order.Index Fossil – a fossil from a short-lived, geographically widespread species known to exist during a specific period of geologic time.
21 ABSOLUTE DATING - DENDROCHRONOLGY Using annual growth rings of treesDates for trees now extending back more than 9,000 years.Bristlecone Pine, White Mountains, CA (pinus longaeva) provides a continuous time scale for last 9,000 years (to 7000 B.C)Provides calibration of radiocarbon dates over most of the last 10,000 years (Holocene epoch)
23 ABSOLUTE DATING VARVE CHRONOLOGY Varves are parallel strata deposited in deep ocean floors or lake floorsA pair of sedimentary layers are deposited during seasonal cycle of a single yearLaminae (similar to annual growth rings in trees) record climatic conditions in a lake or large water body from year to yearCores extracted from sea floor or lake floor are used to date back several million years to 200 million years
25 DATING - ABSOLUTERadiometric dating – based on radioactive decay of ‘isotopes’Decay rate can be quantified because it occurs at a constant rate for each known isotope – “half-life” from parent isotope to stable ‘daughter’ isotopeMeasuring ratio of parent to daughter isotopes determines absolute ages of some rocks.
26 ABSOLUTE DATING ISOTOPES URANIUM–LEAD (U238–Pb206)Half-life: 4.5 billion yearsDating range: 10 million – 4.6 billion yearsURANIUM–LEAD (U235-Pb207)Half-life: 713 million yearsDating Range: 10 million – 4.6 billion yearsPOTASSIUM-ARGON (K40-Ar40)Half-life: 1.3 billion yearsDating Range: 100,000 – 4.6 billion yearsCARBON-14 (C14-N14)Half-life: 5730 yearsDating Range: 100 – 100,000 years