Geology Lectures 1, 2, and 3
Geology Lectures 1, 2, and 3 Geol101
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This 114 page Class Notes was uploaded by Shelby Green on Tuesday January 19, 2016. The Class Notes belongs to Geol101 at Clemson University taught by Dr. Coulson in Spring 2016. Since its upload, it has received 140 views. For similar materials see Physical Geology in Geology at Clemson University.
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Date Created: 01/19/16
Announcements Lecture 1- Intro to Science & Earth’s Formation • PT 1- What is Science? • PT 2- What is Geology? • PT 3- How did the Earth form? PT 1- What Is Science? • science: Method to try to understand things in this world – Built using facts (something that can be repetitively true) – Principles treated like facts today • Not the only way of viewing the world – Ex: Philosophy • This course is based on a scientific POV Scientific Method • Step 0) Observation – Notice what’s going on – Normal human being quality: to notice • Ex: notice the spikes on the skeleton Scientific Method • Step 1) Question – When we first notice something, we question it. • Ex: why did the skeleton have spikes all along its back? Scientific Method • Step 2) Hypothesis – An educated guess – We don’t know the answer yet • Ex: maybe the spikes are a defense mechanism Hypotheses • Testable – If a test cannot be made, the hypotheses is invalid • Predictive – Make a prediction of what we will find when we start doing the test • Written as an“if-then” theory – Ex: If the bones of the spike are actually really thin and weak poor defense mechanism Hypotheses • Can hypothesize on past & future events • Difficult or Easy – Doesn’t matter which it is – Don’t discard a hypotheses b/s it’s too complicated Hypothesis about Dinosaur's body temp Hypotheses- Good or Bad? • 1- Sunlight helps plants grow: Good • 2- Aliens can make flowers grow faster: Bad • 3- Dinosaurs went extinct because a giant asteroid hit the earth 65 million yrs ago: Good • 4- Halo is better than Call of Duty: Bad • 5- Hippo herds help prevent wildfires: Good Scientific Method • Step 3) Data – Collecting samples – Measuring – Etc… Scientific Method • Step 4) Evaluation – Take data and evaluate your hypothesis – Was your hypothesis right or wrong? • Most of the time going to wrong • If wrong: – Eliminated one possibility – Use data to make a new hypothesis – Repeat Thomas Edison: went through over 200 designs before he made a light bulb. “I didn’t fail to make a light bulb Scientific Method • Theory: – A hypothesis with a lot of data from a lot people that support it (a lot of weight behind it) – Strong idea, many people agree with it • Law: – An elevated theory – Theory that has been around a long time – Sometimes exceptions: most of the time holds true • Theories and laws are tested and revised too! Scientific Method • scientific ideasientific data to challenge – Facts, not beliefs • If you want to disprove a hypothesis, you have to show facts and evidence to show otherwise – Ex: cannot use religious arguments to counteract PT 2- What is Geology? • The study of the earth – Not very old (only a couple hundred yrs old) • Earlier approaches: – Catastrophism: everything on the earth formed very quickly b/c of 6 diff catastrophes History of Geology • James Hutton (Scotland): – naturalist who spent years making observations about how processes work in the nature world – Published his work in Theory of the Earth (1795) • Principle of Uniformitarianism – Key idea in his book – Processes in nature today have always worked the same way in the past – “the present is the key to understanding the past” » Ex: every time it rains it will wash away the dirt down the hill – adding upg has formed from little changes – 1800s: became the corner stone of geology History of Geology • Actualism: modified Uniformitarianism – Accounts for change of speed in some processes • Ex: glacier processes used much more wide spread and moved a lot faster – Includes that there has been catastrophic events that have helped modify the earth Incoming! • Meteorites enter earth’s atmosphere at up to 40 km/s • Q: what’s that in MPH? 1 mile = 1.6 km – 90,000 mph • 30 m (~100 ft) diameter meteorite @ 15 km/s impacts w/ energy = 4 million tons of TNT • Meteor Crater, AZ. > 1/2 mile > 600 ft PT 3- How Did Earth Form? • Over 6 bya (billion years ago): No solar system, just a nebula of H atoms • Nebula: a gas cloud Forming the Solar System • Nebular Hypothesis: • Step A) Gravity still affecting hydrogen atoms in the nebula – Hydrogen atoms attracted to each other slowly over time • Step B) Solar Disk Model – The cloud flattened out once hydrogen accumulated Nebular Hypothesis con’t • Step C) Protostar: – all the hydrogen accumulates into a circular shape (6 Ga [billions years ago]) • Step D) Fusion: – Needs to rise several million degrees celcius • densely, and the vibrational energies of the attracting H causes the temp to rise – The heat energy allows fusion to occur and it becomes a star (our star) • Surrounding disk begins to See file 1b on blackboard cool to see animated visuals Forming the Planets • Planetary accretion: – Debree collides with each other; the masses will stick together to make a bigger object • asteroids meteors planets – Ex: Playdoe sticks together to make a bigger and bigger ball • 4.5 Ga (billion years ago) earth has reached a consistent size – Starting age for planet earth Forming the Planets • Planetary accretion still happens! – Planets are still being created Forming the Earth con’t • Theia Impact: – planet called Theia major collision with an other – Probably a couple thousand miles of impact – Earth gets reshaped through this massive collision Theia Impact Aftermath • 1) Lunar formation – The moon is debree that broke off from earth during the theia impact • The moon is moving away from the earth every year Theia Impact Aftermath • 2) Molten planet: – The energy increase made the Earth molten for a period of time – Allowed something weird to happen to earth… Density • Density: the mass of something per unit of volume • How heavy is it for its size – Ex: cannot mix oil and water b/c the oil is less dense than water – Ex: different density rocks don’t act like oil and water b/c they’re solids Theia Impact Aftermath • 3) Density stratification: – Molten (liquid) separates like oil and water – Higher density stuff sunk to the center and the lower density rose up to the surface – Eventually, the molten period cooled and this explains the layers of the Earth Review- Things to Know • The scientific method • Good vs bad hypotheses • Uniformitarianism • The age of Earth & how it formed • Consequences of the Theia Impact • Note- These ‘review’ slides do NOT list everything you should know; they’re a short list of SOME of the main topics Announcements Geology in the News • Satellite data is giving geologist new info about how and why the glaciers on Greenland are melting Lecture 2- Plate Tectonics • PT 1- Layers of the Earth • PT 2- Plate Tectonics Basics • PT 3- Development of Plate Tectonic Theory • PT 4- Types of Plate Boundaries PT 1- Layers of the Earth • Review: Theia impact & density stratification Compositional Layers of the Earth • 4 layers, defined by chemistry (aka composition) – thingto know chemical/composition mean the same • 1) Crust (8-45 km) – Light/low density elements (Si, Al, O2) – Iron and stuff like that is a small percentage ca 4k miles Types of Crust • Continental crust: less dense, why continental crust tend to pile up higher • Oceanic crust: denser, why oceanic crust tends be to lower Compositional Layers continued • 2) Mantle (45-2900 km below the surface) – Denser elements – More iron and nickel present Compositional Layers continued • Core • 3) Outer core: high iron and nickel concentration • 4) Inner Core: almost solid iron (like 93% iron, 6% nickel, 1% other things) Physical Layers of the Earth • 5 layers, defined by physical (aka mechanical) strength 1) Lithosphere: – much thicker than the crust, equals almost all the crust and the upper part of the mantel. – A brittle material that is very strong but will shatter if you apply enough force Physical Layers of the Earth 2)Asthenosphere: – Not brittle, ductal (what word was he saying) / plastic material • Like a melted chocolate bar – Low strength, give away easily, less solid but still not liquid Physical Layers of the Earth 3) Lower Mantle (Mesosphere): – Deeper in the earth, so expected to be more ductal – But instead, it starts to behave more brittle again – why? • B/c the amount of pressure that is being applies to this layer • Also b/c of the type of material: stronger than the material above it Physical Layers of the Earth Core 4) Outer core: most ductal 5) Inner core: very brittle Layered Earth • Can’t use terms interchangeably • Every other: – Brittle, ductilel, brittle, ductile, brittle… PT 2- Basics of Tectonics • Why do we care about tectonics? What is Plate T ectonics? • geology developed in the 1960sry of • KEY to plate tectonics: The lithosphere is divided into pieces (PLA TES) Those plates move around the surface of the earth Like an ice burg, solid but drifts around the ocean. Plates do the same thing Map of the Plates • Continents, oceans, & plates • The names of the plates don’t always match up how you would expect • Not corresponding to major crust or oceanic boundaries • Some plates have both oceanic and continental Antarctica: Then & Now Today vs 90 Ma (million years ago) PT 3- Developing Plate T ectonic Theory • Alfred Wegener’s Continental Drift • Popular scientist in the 1920s-1920s • He shapes of the continents looked like a puzzle Data Supporting Continental Drift • Mountain belts: • many mountain ranges match up like Greenland Europe • Mesosaurs: • Little lizard that lived about 300 Ma • Found at the end tip of south america and thend tip of africa • Many people thought he was crazy; ppl didn’t understand how continents moved 1940s: New Research Mid Ocean Ridge (MOR): • World war II and cold war: submarines • Needed navigation charts • To put these charts together, scientists did a lot of tests on the ocean floor • Discovered the mysterious mid ocean ridge See file 2b Magnetic Anomalies • Magnetic Reversals: same on either side of the ridge • The rocks on the sea floor, contained little iron crystals that acted like magnets Age of the Seafloor Also found age anomalies of seafloor rocks: • The hotter colors are new rocks • Cooler colors are the older rocks • The rocks get older the further away from the ridge Continental Drift Revisited • Seafloor spreading: (1960s maybe) • The Midocean ridge acts as a volcano all along the sea floor • At some point in the past, the earth magnetic field was reversed and pointed south instead of north • The crystals must have been responsible • As the sea floor spreads apart, the continents get spread apart • Wegner’s theory was proved How Do Plates Move? • Convection: helps the plates move • Convection cells acts like a pot on stove • Ex: pot on stove, warms water at the bottom the fastest-density drops so it rises, then it cools away from the heat source-density rises so it drops, starts cycle again • BUT convection isnt fast enough to account for all the motion. There are other components as well New Hypotheses • (Ridge Push Model) new rock forming at the top of the mid ocean ridge, incline.As it new rock develops it pushes the existing rock/plate downhill and away See file 2c New Hypotheses • Slab Pull Model: • Plates get pulled back into trench • Once part of the plate enters the trench, the whole plate will get pulled down • Slab Suction: • Sucks part of the asthenosphere (peanut butter consistency) • Like the titanic Run Plate Run! • How fast do these things move? • A slow jog at about 10 cm per year • About the size of your average star wars action figure Plate T ectonic Speed • Los Angeles & San Francisco are actually on separate plates • Q: If LA and SF are 300 miles apart and moving towards each other at this rate, how many years until they’re side by side? • (300 miles)(1 mi/5280 ft)(1 ft/12 in)(1 in/2.54 cm) =answer/(10 cm) • =almost 5 million years PT 4-Plate Boundaries • There are no ‘voids’between plates • What happens at the boundaries where 2 plates meet? • 3 options: • 1) Pull away from each other • 2) Run into each other • 3) Slide past each other • California example in last slide *Study Hint* • ‘Boundary’, ‘margin’, ‘edge’, etc are synonymous • Just referring to the areas where one plate borders a different plate 1- Divergent Margins • Two types • 1a) Mid-ocean ridge: • Oceancrust from oceancrust See file 2d Divergent Margins • 1b) Continent splits = rift valleys • Continental crust from continental crust • Ex: eastern part ofAfrica • Tend to have volcanoes on the ridges *Study Hint* • Rift valleys and mid-ocean ridges ARE types of plate boundaries, they’re just specific types of divergent plate boundaries 2) Convergent Margins • Two types • 2a) Subduction zone: Ocean-continent collision • Volcanic activity & big earthquakes • Trying to push down a continental crust is like trying to push a cork underwater • Ex:Andes mountains (lots of volcanoes) • this is why chile and argentina experience bad earth quakes See file 2e 2- Convergent Margins • 2b)Collision zone: continental crust wont push down (like a cork) so they’ll just go up • Not volcanic • Some earthquake activity • Ex: apalachian mountains *Study Hint* • Subduction zones and collision zones ARE types of plate boundaries, they’re just specific types of convergent boundaries 3- Transform Margins • Ex: California • Earthquake activity See file 2f + 2g Modern Boundaries • Plate actions are linked Review- Things to Know • Layers of the Earth (both systems) • History of tectonics • Plate boundary types & their features • Important plates Review- Noteworthy Plates • Nazca • North American • South American • Eurasian • Pacific Announcements st • 1 exam 2 weeks from today Geology in the News • Seismic activity in the Pacific Northwest linked to subduction of the Juan de Fuca plate beneath N. America – 1 should see volcanoes – Then seismic activity should occur (earthquakes) Lecture 3- Minerals & the Rock Cycle • PT 1- Chemistry Review & Mineral Basics • PT 2- What is a Mineral? • PT 3- Mineral Properties • PT 4- Mineral Groups • PT 5- The Rock Cycle Rocks & Minerals • Why do we care? – There are minerals in foods, cosmetics, construction (like dry wall), technology, and jewelry. PT 1- Basic Chemistry • Atoms: building blocks of all matter – Protons/neutrons make up nucleus • Cannot change the # of protons for it to be the same element – Electrons rotate around the nucleus • Can lose and gain electrons and still be the same element • Atomic Number: the # of protons in the nucleus • Element: # of protons tells you which element they belong to Periodic Table of Elements Chemistry of Earth’s Crust PT 2- What is a Mineral? • How do we define something as a mineral? – 5 CRITERIA Defining Minerals • 1) Non-synthetic: form in nature Defining Minerals • 2) Inorganic: – Organic material: fats, proteins, DNA, things you would find in living things OH O OH O OH OH O HO OH N H H OH HO OH O fructose ribose proline H3C O OH O O O N O H C O CH3 3 Defining Minerals • 3) Crystalline: – always get put together the exact same way – Follow a crystal structure/pattern – Emorphis: (bottom right picture) not a mineral like volcanic glass Defining Minerals • 4) Solid – State is determined by Temp/Pressure conditions • Gas Condenses Evaporates • Liquid Freezes Melts • Solid Defining Minerals • 5) Set chemical composition/formula – Ex: H 2, NaCl (hyalite), SiO (q2arts) • Some substitutions occur: – Ex: shortage of sodium, potassium can substitute in place of it PT 3- Mineral Properties • How do we identify specific minerals? – 4 to 5 thousand diff minerals – So test the properties of a mineral Mineral Properties • Color: some minerals are always the same color so color can help identify it – Many minerals come in a wide range of color This is a picture of all the same mineral Mineral Properties • Streak: tells the color of the mineral if you grind it up into powder – Rub mineral across ceramic tile • 9 times out of 10 powder is the same color as the mineral This mineral is black but its streak is reddish/brownis Mineral Properties • Hardness: how tough the mineral is • Moh’s Scale: 1-10, 10 being the hardest Mineral Properties • Tools: + or minus one number percent of error • Hardness is less than 2.5 if you can scratch with nail • Pocket knife: hardness of 5 – Can be variations in tools hardness and even mineral hardness Mineral Properties • Luster: how shiny – Vitreous: glass-like – Silky: soft glow/florescent glow – Resinous: looks like its covered in tree sap Mineral Properties • Effervescence: bubble and fizz – Some when exposed to weak acid will start to dissolve • HCl + CaCO = 3O + Ca2+ OH + Cl Mineral Properties • Crystal Form: shape the mineral should have when you have crystal formation – If it could grow in ideal conditions • This ex) hyalite – The big cube grew in ideal conditions (bottom right pic) – The bottom part did not (bottom right pic) Mineral Properties • Breakage Patterns: how the mineral will break • Fracture: irregular pattern for a break – No rhyme or reason for its breakage ex: quarts Mineral Properties • Breakage Patterns • Cleavage: breaks along very plat smooth surfaces (cleavage planes) • Ex: hyalite • # of planes/the angle the planes meet at help define the mineral PT 4) Common Mineral Groups • Minerals grouped by a common anion – Anion is a negatively charges particle (left side of the periodic table) – CLASSIFIED BY ANION • Many groups exist…. Mineral Groups • Sulfides (S): a single atom as an anion – ___+ sulfur = new mineral • Oxides (O): a single atom as an anion – ___ + oxygen = new mineral • If you have __ + oxygen. Take away the oxygen and you have the ___ • The harder ___ is to extract, the more expensive the process is – Note: fools gold has no gold in it at all Mineral Groups • Sulfates (SO )4 SO4 used an anion – Common on the surface of the earth • Construction: ex) dry wall • Medical industry: ex) plaster for casts Mineral Groups • Phosphates (PO ): P44 anion – Not as common on the surface of earth • Ex: – fertilizer (mininggrinding up phosphorous) – Bones and teeth » Broken arm how to get those phosphate crystals to grow back together nice and strong? Mineral Groups • Carbonates (CO ): 3O3 anion – Invertebrate organisms often form shells out of carbonate – Coral reefs are made out of carbonate – Many invertebrates that are microscopic have carbonate shells (ex: plancton) • When the organism dies, the shells remain, build up over time, and become really thick – Effervescence Mineral Groups • Silicates (SiO4): – Bond together in a particular pattern • Tetrahedron – Easy to form Tetrahedra • Polymerization: take the little tetrahedra and bond them to one another • 2 tetrahedra never share more than 1 oxygen atom between them Types of Silicates • Sub-groups depend on how tetrahedra polymerize • Island Silicates: they don’t polymerize, they’re bonded to positively charged cations Types of Silicates • Chain Silicates: – Tetrahedras combine to make a long chain – The single vs. double chains have diff properties (Two chains stuck Types of Silicates • Sheet Silicates: sheet like – Covers an entire flat geometric (2D) surface – Ex) works like a sandwhich • 1 layer of tetrahedra Notice the Cleavage plane • 1 layer of positively charged ions • 1 later of tetrahedra **easy to remove layers of sandwich just like it’s easy to remove sheet silicates Types of Silicates • Framework Silicates: – 3 dimensional network – The most common minerals at the surface • Ex: quarts PT 5- The Rock Cycle • Rocks and Minerals are not the same thing – Rocks: one or more minerals stuck together and maybe some other nature stuff too PT 5- The Rock Cycle • Only three types of rocks form on Earth: The Rock Cycle • Differentiated based on HOW THEY FORM • Linked via the Rock Cycle Rock Cycle • Magma: liquid rock (similar to lava), associated with volcanic eruptions, will convert to solid when temp cools • Igneous Rocks: when magma cools and crystals form together to make a solid Rock Cycle • Weathering: Rock acted upon by surface processes which breaks it down Rock Cycle • Erosion: a transport – Ex: running water (streams, rivers, etc), or wind Rock Cycle • Deposition: when the sediment settles after erosion Rock Cycle • Lithification: turned into stone • all the debree from deposition form together to form sedimentary rocks Rock Cycle • Metamorphic Rock • Metamorphism: change form – Temp and Pressure increases as build up occurs – Many Minerals don’t react well to high temp and pressure so they’re forced to change in order to withstand the new Temp and Pressure – This forced change creates metamorphic rock Rock Cycle • Increase Temp to the melting point, and you’re back to magma, the cycle is closed • Note ‘shortcuts’… it’s not a 1-directional cycle melt Lower T META- MAGMA MORPHIC ROCK T/P increase IGNEOUS SEDIMENTARY ROCK Rock Weathering Erosion Lithification Review- Things to Know • Composition of the crust • Difference between rocks and minerals • Properties of minerals • Groups of minerals • The rock cycle