GEOL 1040 notes PDF

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Lecture notes from all classes with highlighted topics of importance. Also contains review session notes of important topics for 2 midterms and the final exam....

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Professor Lon Abbott [email protected] Day 1 Powerpoints WITH PICTURES on canvas     

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Human life is determined by Geology o Sustains us using farmland and water Gold rush started in idaho springs in 1890 o Boulder being the service town to the gold rush Gold minerals are important to the current CO economy o Along with mountain recreation Uniformitarianism: similarities in structure between present and past Plate Tectonics o Subduction zone  Where one plate dives down against another  Produces volcanoes  Water introduction from oceanic plates decreases melting temperature o Oceanic crust is heavier than continental crust Formation of Colorado o Offshore volcanic islands (CO) collide with Wyoming continental crust o Gneiss rock formations formed o 500 Ma CO was a beach on the coast o Sea level was rising then, temporarily covered by a shallow sea o 300 Ma Pangea started to form o Landscape was dominated by sand dunes  Created sandstone which is what’s used for building CU Campus o 255 Ma Stromatolites dominated CO  Layered rocks and pond scum bacteria o 150 Ma Dinosaurs rule the state o 100 Ma another sea encroached Colorado, making it a beach state again  Completely under the sea 90 Ma  Birds flew above  Oil rich mud accumulated in this sea o 68 Ma the sea retreated from the front range  Caused by mountain ranges rising o Still working with effects of gold rush  Acid water leaks from mines  Leaks into springs used for water  Effects major CO export (COORS) o Current mountains were covered in sediment and eventually washed away to expose the current mountain range

Sedimentary rocks Weathering is the decomposition of rocks o Mechanical (physical) weathering  Breaks it down  Doesn’t change its composition

Chemical weathering  Changes the actual mineral composition of the rock  Quartz is resistant to chemical weathering, forming sand  Other minerals break down to form clay minerals/mud Erosion is the removal of decomposed rock from weathering Weathering creates sediment, erosion transports sediment o Transports it to river deltas or the bottom of the ocean o Buried sediment is compressed into sedimentary rocks o Sedimentary rocks have horizontal layers o Cross beds are when the layers are inclined Two Sub-classes of Sedimentary rocks o Clastic (detrital)  Pre existing rocks that are cemented together  Conglomerate sized material  Bigger than 2 millimeters  Chunks of rock  Sandstone  1/16-2 millimeters  Siltstone  Less than 1/16 of a millimeter o Biochemical (chemical)  Form by biochemical reactions that form new minerals from dissolved ions  Saltwater dissolving in a pan leaves salt  Limestone  Composed of calcite, the mineral that most marine life make their shells from  Evaporites  Evaporation of large amounts of saltwater  Leaves several types of minerals  Chert  Made of microscopic quartz  Smooth interesting texture and color  Coal  Compressed organic carbon and oil  Coal= swamps in CO 67 Ma  Paleontology tells us past landscapes based on current rocks o Fossils tell us what plants and animals lived there o Poop= coprolite  Steno’s Principles (Sedimentary rocks)  Lived during reformation, devout Catholic, very good surgeon o Original Horizontality  Deposited horizontally because of Gravity  Disturbances in horizontal formation most likely means tectonic activity o Superposition  In and undisturbed stack of sediment the top is the newest and the bottom layer is the oldest o Lateral Continuity  Sedimentary layers were deposited in continuous sheets o

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Disturbances in horizontal sheets means possible tectonic activity AFTER formation Mineral, Igneous Rocks, and Metamorphic Rocks  Minerals o A mineral is  Naturally occuring  Inorganic solid  Crystalline (ordered molecular structure  Halite (table salt), cubic NaCl  Definite chemical composition o Quartz  SiO2 (silica) o 98% of the earth’s crust is composed of 8 elements  Oxygen  Silicon  Aluminum  Magnesium  Calcium  Iron  Sodium  potassium o Silicate group  Silicon and oxygen together  Rock Forming Minerals  Building block is Silica tetrahedron (1Si, 4Os)  Combines with other elements in nature o The more iron and magnesium a rock has, the darker it is  Less silica  Darker color  Cools faster o More silica=lighter color  Silica melts first, raising high silica magma rises to the top of volcanoes 

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Bowen's reaction series, memorize

Non sliilates are less common but very important o Carbonate minerals make limestone  (CaCO3)  Oxide and sulfide o Ores for major metals o Major part of Colorado mining  Sulfates include gypsum o Gypsum is used in wallboard  Halides o Salt (NaCl) o Other important compounds  Phosphates o Essential nutrient for life o Environmental pollutant from fertilizer IGNEOUS ROCKS  Form from cooling magma  Magma is formed deep in the earth  The lower the silica the higher the melting point o Partial melting of mantle rocks (low silica) produces magma with more silica than its source  The magma cools and forms crystalline igneous rocks 

Surface eruption  (aphanitic)=fast cooling, small crystals o Beneath the surface  (phaneritic)=slow cooling, bigger grains o Liquid magma rises  Some erupts, some stay in a magma chamber beneath the surface Second level classification o Extrusive (volcanic)  Volcanic erupted  Aphanitic  Microscopic crystals o Intrusive (plutonic)  Cooled beneath the surface  Phaneritic  All mineral crystals are visible  Granite o Glassy texture means no crystals were formed o Porphyritic  Mixed sized grains  More complex drying history o Pyroclastic (fragmental)  Formed during volcanic explosion  Mixed fragments, angled shards inside  Third level classification o Composition/ how much silica  Mafic  Dark color= low silica  Basalt  Silic (felsic/granite)  Light color= high silica  Granite, intrusive o

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METAMORPHIC ROCKS  Changed the texture or mineral composition due to heat or pressure without melting  Type is determined by o Temperature o Pressure o Type of rock being metamorphosize  Parent rock called protilith o Water presence o Duration of Pressure and stress  Uniform pressure on all sides is called lithostatic pressure  Buried rock  Causes foliation  vertical alignment of mineral crystals  Extra pressure from plate tectonics cause Non uniform stress on one side  Convergent plate boundaries  2nd level classification o Foliation (vertically aligned crystals from converging)  Mudstone>slate

Clay minerals lineup making a smooth clean sheet Higher temp. and pressure it changes to Phyllite  Mica minerals grow, giving it a shinyish lust look  Even higher temp  Schist  Mica grows more becoming visible  Very high temp  Gneiss  Dark and light bands form As it gets closer to melting point  Migmatite (high silica)  Half igneous half metamorphic Metaconglomerate  Conglomerate pebbles get stretched and squished vertically o Non foliated (based on protolith) quartz>quartzite limestone>marble basalt>greenstone mudstone>hornfels  In the absence of differential stress o Contact metamorphism Due to heat alone Produces non foliated rocks o Burial metamorphism Due to high uniform pressure and temp Produces non foliated rocks o Regional metamorphism At plate boundaries from pressure Form foliated rocks o Hydrothermal metamorphism Hot water passing through rocks Form at divergent boundaries  

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HOW ROCKS DEFORM  Stress and strain o Strain  Deformation of a rock due to stress  Elastic- the change of shape can be reversed (rubber band)  Brittle- the material cracks  Causes earthquakes when it snaps  Plastic (ductile)  Material flows o Influencers  Temp  Hot  Plastic  Cold  Brittle  Strain rate  High strain

 Brittle Low strain  Plastic Rocks intrinsic strength  Thick beds- less folding  Thin beds- more folding 

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Faults o Formed brittly from cracking o Strike slip  Plates slide past each other (shear) o Normal faults  Extension of earth's faults  Hanging wall slides down relative to the footwall  divergent o Reverse faults  Hanging wall moves up the footwall  Convergent  Types of stress (at plate boundaries) o Compressional o Extensional o Shear  Sliding  Types of folds (rocks bend without breaking) o Anticlines  Arc shaped like a triangle  Limbs point away from each other o Synclines  Bowl shaped o Monoclines  One limb  Anticlines and synclines are often connected to form a train of folds  Erosion of hard vs soft rocks is what creates mountain topography

GEOLOGIC TIME  Relative Time o Which rock came before another o Not a specific dated year  Numeric Time o Determines how old a rock is in years  Fossils o Fossils at the top are the youngest, bottom are oldest o Fossils did not go extinct and come back on top  Life on earth evolves  Index Fossils o Distinctive fossil that was only alive in a distinct period

o Went hard and goes extinct quickly o Zoic for eons and eras  Phanerozoic o Cenozoic  Most recent  Looks most like current animals o Mesozoic  Middle ages o Paleozoic  Oldest life and fossils  Precambian o Before life  Time scale was complete around 1850 o Discovery of radioactivity in 1898  Changes in the nucleus in atoms  Isotopes have a different number of neutrons  Isotopes o The more neutrons you add the more it becomes unstable  12C and 13C stable  14C unstable→ 14N o Unstable isotopes will spontaneously decay  When unstable isotopes decay it ejects an electron  Turns a neutron into a proton changing the element  Decay occurs at a Regular Rate  Half life= half of the atoms are now daughter atoms  Start at 1 - ½ - ¼ - ⅛  Measure how many half lives have passed by measuring how many parent and daughter atoms there are  (# of ½ lives since birth X calculated duration of half life) = date of rock o Daughter/parent ratio is reset by by heating  Igneous and metamorphic rocks can be radiometric dated o Sedimentary rocks are not heated so radiometric dating does not work  Fossils give sedimentary rocks dates UNCONFORMITIES  Time gaps in the rock record  Angular unconformity o Sedimentary layers above and below unconformity o Rocks are tilted at different angles o Indicates tectonic tilting followed by erosion  Nonconformity o sedimentary/igneous extrusive on top of metamorphic/igneous intrusive o Indicates major erosion and mountain building event  Disconformity o Gap in time between two parallel beds of sedimentary rocks o No tectonic activity o Nondeposition or mild erosion o Often caused by a regression of sea level

PLATE TECTONICS  Movements o Diverge  Pull apart on normal faults  Partially melted peridotite forms basalt (mafic) through mid ocean ridges o Converge  Subduction  If one or both plates are oceanic (more dense)  Oceanic-Oceanic  Triggers melting and volcanoes to erupt  Water comes down with oceanic crust and lowers melting point o Slide horizontally (strike slip)  Cause earthquakes, volcanoes, and mountain building  Layers of the earth o Composition  Crust  Very thin outer layer  Highest silica rock (more buoyant)  More silica=less runny lava  Silica melts first, high silica magma moves to the crust  Mantle  Low silica  Middle layer  Made of Peridotite (ultramafic) partially melts forming basalt (mafic)  Core  No silica o Deform Behavior  Lithosphere  All of the crust and upper mantle  Rock behaves brittly (more earthquakes)  Oceanic crust is thin  Made of basalt (dense)  Continental crust is thick  Made of less dense rocks  Asthenosphere  Convection- transfer of heat by movement  Solid flowing rock  Convection in asthenosphere drives movement of lithospheric plates  Mesosphere (lower mantle)  Faults cause/near movements on exam 

VOLCANOES o Stratovolcano (composite volcano)  At subduction zones  Built up of lava and ash o Calderas  Form when silica and gas content is high

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 Massive explosion Continental Collision Zone o Form non volcanic mountain zones

CONVERGENT/DIVERGENT boundaries on power point Divergent boundaries o Mid ocean ridges o Cause basalt volcanic eruptions o Oceanic plates are made of basalt  Peridotite (Ultramafic) rock in mantle partially melts to form basalt (mafic)  Convergent Boundaries o Subduction  Oceanic (less dense) plate subducts  2 Oceanic plates= chain of volcanic islands  Continental vs oceanic forms volcanoes on the shore  Partial melting produces andesite  Andesite is less dense and more sticky than basalt  New continental crust is formed at subduction zones because of the more buoyant silica in the andesite  Andesite traps gas causing explosive eruptions  c o Collision  Continental plates forming mountains HOT SPOT THEORY  Plumes of hot magma pierce the crust creating a chain of volcanic islands  Island are older -> younger opposite of plate movement 

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PART 2 after midterm BEFORE COLORADO   

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13 Billion years ago the universe was created 300,000 years after the big bang, the universe density decreased so light could travel CMB o Cosmic microwave background o Light areas are more dense with light and hydrogen o Remnants of electromagnetic radiation that backfills space Before Colorado o Hydrogen compressed to helium at >10 million degrees  Formed first generation of stars o Stars burn H until its used up  When its used up it collapses, heating up and burning through another element

Iron Fe doesn't burn, process stops at Fe Star then explodes (supernova)  Created the bigger elements we have now for raw materials  Earth formed about 4.6 billion years ago with the rest of the planets in the solar system Dense iron sank to form the core 4.5 Ma earth collided with Orpheus, creating the moon  Earth has largest moon Earth was Covered in a magma ocean  Magma cooled and formed a super dense oceanic floor of komatiite  Continental crust is formed at subduction zones or granitization  Granitization  Partially melting and remelting of felsic volcanic rock  More common a long time ago when the earth was hotter  Still seen in iceland  Plate tectonics are driven by heat= extra fast back then o Terranes (small chunks of crust) were welded together in tectonic collisions o Archean rocks show how plate tectonics started  Dark Mafic greenstone belts  Resembles oceanic crust  Light silic gneiss belts  Wilson Cycle o The assembly of a supercontinent is inevitable o Oceanic crust submerges, pushing continental crust together o First supercontinent 3.3 Ga (Vaalbara)  Contained world's oldest life (fossils)  

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Detrital Zircon o Zircons are nearly invincible  They form in igneous rocks like granite  Zircons collect in sediments o Zircons contain Uranium (U-Pb dating)  Sediment doesn’t heat  Can date the igneous cooling of Zircon  Cant date the sediment forming o DZ Study  Age vs frequency distribution  Sedimentary rock has to be younger than the youngest Zircon o Cross Cutting Relationship  The rock that was cut through is older than the dike

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PROTEROZOIC EON o Wilson cycle (supercontinents)

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Hot spots create mid ocean ridges separating continental crust North america at the dawn of Proterozoic forming supercontinent Nuna  First supercontinent  Formed about 1700 Ma  Welded australia and antarctica to north america Colorado and Wyoming border (Nuna)  Wyoming is continental crust  Adjacent plate subducted (oceanic crust) to form the Colorado volcanic island arc  Many granodiorites (boulder creek) are from this cooling magma  Colorado volcanic arc collided with Wyoming creating a coastal mountain range  Mountains were quickly eroded, exposing boulder creek granodiorite  Foliated gneiss and schist formed from differential stress  This subduction zone went from SW to NE  Yavapai Orogeny collision  Colorado was added to Proto north america Nuna  Happened along the Cheyenne belt line Mazatzal Orogeny  Another volcanic island arc added to Nuna  This shifted the coastline from Colorado to West Texas 1400 Ma Berthoud (silver plume) granite intruded the Yavapai suture zone in Colorado  Suggests a mountain building activity called Picuris Orogeny Nuna broke up around 1300 Ma  Rifts related basalts erupted (called Mckenzie dike swarm) By 1100 Rodinia supercontinent was being formed  Australia and antarctica joined the north american west  Grenville Orogeny  Rift formed in the middle of North America but failed  Runs from Lake Superior (Michigan) to Oklahoma Pikes Peak Granite being formed at the same time (1100 Ma)  Youngest and biggest of Colorado’s proterozoic granitic batholiths Rodina broke up around 750 Ma  Australia and antarctica split west forming the pacific ocean  North America was stretched and cut with normal faults along the Wasatch/ Las Vegas line  Sandstone dikes intruded the pikes peak granite (tava sandstone)  Likely 680 Ma related to Wasatch line Colorado diamonds  Line of diatremes to Wyoming  Diatremes  Small volcanic pipes that erupt explosively due to their gas rich magma  Diamonds form in the mantle deeper than 100 Km   PHANEROZOIC SEA LEVEL  Transgression and regression

When depositional environments change, the characteristics of the sedimentary rocks change Called facies (varying sedimentary characteristics) o Several different facies where the land meets the sea o Sea level is always rising or falling Sand settles closer to shore Mud is deposited further out than sand Lime is the farthest out  Creates limestone on ocean floor  Marine plankton have lime shells which make up a lot of the ocean floor This pattern shows in the grand canyon  Ocean rising (transgression) o Sloss cycle Second order sea level cycles More mid ocean ridges=flood continents and displace water (transgression)  Sea level rises during continental breakup Colorado was a beach 500 Ma during transgression  Sediment size o Conglomerates, sandstone, then siltstone Energy of transport o Getting closer to Boulder, bigger conglomerates Desserts in arizona are sandstone Boulder is closer to the ancestral rockies No use of topography, just sediment types o

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PALEOZOIC COLORADO  The Cambrian through the Mississippian  Sea level rises with continental breakup  Passive margin o A coastline facing an open ocean o Few earthquakes, volcanoes, or mountains  Coastline stood at the grand canyon 520 Ma o Layered beach sandstone and marine shale o Transgressional layering  Unconformities caused by rapid regression and erosion  Silurian limestone fell into erupted volcanoes protecting them from erosion  Conglomerate sized rocks then filled Colorado after a regression o Formed by ancestral rocky erosion o Aspen was a basin in ancestral rockies o Formed by erosion of ancestral rockies followed by a mountain building episode o Weakness in crusts caused by supercontinent breakup and collision  Cut on the knuckle analogy  Form normal faults at divergent boundaries  Sediment ripples o One way current (river)  Asymmetrical ripples  Gradual uphill slope and steep downhill slope

Ocean  Symmetrical waves  Waves going both ways  Creates even ripples PANGEA AND ITS BREAKUP  Still intact in the triassic o Impacted global climate  Broke up in jurassic  Formed about 300 Ma o Proto atlantic ocean (lapetus) closed o Parts of north america were covered by a shallow sea o Newly formed appalachians were above water level o Colorado was close to the equator during the pennsylvanian   Life on earth o First forest on earth o Removed CO2 from the atmosphere  Cooled the planet  Many continents were on the south pole  Glacie...