GEO Exam 1 Study Guide PDF

"Study Guide" GLY2010C Exam 1\ The exam will be true/false, multiple choice on a Scantron. All material will come directly from\ presentations. Make sure you know what I have presented in class. There is an extended guide\ at the bottom of the document, but you should have a deeper understanding of...

"Study Guide" GLY2010C Exam 1\ The exam will be true/false, multiple choice on a Scantron. All material will come directly from\ presentations. Make sure you know what I have presented in class. There is an extended guide\ at the bottom of the document, but you should have a deeper understanding of the following\ topics, I will ask more in depth questions on them:\ Understand the age of the Big Bang, Earth, Solar System and Universe\ Heliocentric v Geocentric concepts\ Chondrites\ Journey to the center of the Earth\... what did we observe? What did we pass?\ Composition and Density of Earth layers\ Structure of the atmosphere with respect to density\ Stress v Strain\ Types of stresses w examples\ Population of Earth and related issues\ Crust, mantle, core. Oceanic crust v continental crust. Lithosphere v asthenosphere.\ Plate motion, rates and ages\ Formation and destruction of crust\ Be able to describe the various tectonic plate boundaries\ Concept of Rock Cycle\ Hot Spots\ Sea-floor spreading\ Understand the evidence used to support Continental Drift and Plate Tectonics\ Get good exercise, sleep and food leading up to your exam.\ https://learningcenter.unc.edu/tips-and-tools/studying-101-study-smarter-not-harder/\ Danny **EXAM 1 study guide (extended)**\ ------ How do we know Earth spins? - Foucault's Pendulum - A freely swinging pendulum maintains its motion, but its apparent direction changes due to Earth's rotation. This experiment proves Earth spins independently of external forces - Coriolis Effect - Fluids (air and water) curve due to Earth's rotation (e.g. hurricanes spin counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere) - Star trails - Long-exposure night photos show circular star paths around the North Star (Polaris) - Day-Night Cycle - The sun does not move across the sky -- instead Earth rotates, making it appear like the sun rises and sets Geocentric v heliocentric views of the solar system - Geocentric (Earth-centered) - Proposed by ancient Greeks (refined by Ptolemy) - Idea: Everything (sun, moon, planets) orbits Earth - Problem: Couldn't fully explain retrograde motion (actual movement of an object in a direction opposite to the direction of other objects in its system) - Heliocentric (Sun-centered) - Proposed by Copernicus, confirmed by Galileo - Idea: Planets orbit the Sun in elliptical paths (Kepler) Ptolemy - Developed the Geocentric model using epicycles (smaller circular orbits inside larger orbits) to explain why planets appeared to move backward (retrograde motion) - This was wrong but remained accepted for over 1,400 years until Copernicus and Galileo disproved it Eratosthenes calculations, no math, just concepts - Used the angle of sunlight in two locations at different distances to estimate Earth's circumference - Summer solstice -- the sun was directly overhead in Syene (modern Aswan, Egypt) but cast a shadow at an angle in Alexandria (north of Syene) - Found Earth's size over 2000 years ago with remarkable accuracy Distances to celestial bodies: Moon, Sun, Nearest star - Moon: measured using parallax (viewing the Moon from two different Earth locations) -- 384,400 km (\~1.28 light-seconds) - Sun: estimated through the transit of Venus and triangulation -- 150 million km (\~8.3 light-minutes) - Nearest star: measured by stellar parallax (tiny shift in a star's position as Earth orbits the Sun) -- 4.24 light-years Distance measured as light years/minutes/seconds - Light-year: distance light travels in one year (\~9.46 trillion km) - Light-minute: distance light travels in one minute (\~18 million km) - Light-second: distance light travels in one second (\~300,000 km) ------ Doppler effect/doppler shift: in light and sound - Doppler effect in sound - When an ambulance approaches, its sirens sound higher (waves are compressed) - As it moves away the siren sounds lower (waves are stretched) - Doppler shift in light - Redshift: if a star moves away, its light waves stretch, shifting toward blue - Blueshift: if a star moves towards us, its light waves compress, shifting toward blue - Hubble's discovery: most galaxies are redshifted, meaning the universe is expanding Expanding universe theory - Edwin Hubble (1929) discovered that galaxies are moving away from us (observed the distant galaxies' light is shifted toward the red end of the spectrum) - Further the galaxy, the faster it moves away - Big Bang Theory: the universe began as a tiny, hot, dense point \~13.8 billion years ago and has been expanding ever since Age of Universe including supporting evidence - Redshift of galaxies (expanding universe) -- Hubble's Law - By measuring how fast galaxies are moving away and using extrapolation, we can estimate how long ago the universe was extremely small - Cosmic Microwave Background (CMB) -- leftover radiation from the Big Bang - Gives us a "snapshot" of the early universe, showing its conditions 380,000 years after the Big Bang - The universe's age was calculated by measuring this radiation's temperature and structure - Nucleosynthesis -- formation of hydrogen and helium in the early universe - Match the predicted chemical makeup of an expanding universe - Oldest stars and star clusters - The oldest known stars are \~13.2 billion years old, meaning the universe must be older than them - Globular clusters (ancient star groups) help confirm this estimate Rate of expansion of the universe - Hubble's Law - The further a galaxy is, the faster it moves away - The relationship between distance and speed is measured using the Hubble Constant (H~0~) - Supernova observations - Scientists study Type la supernovae (exploding stars) to measure cosmic distances - These revealed that the universe's expansion sped up about 5 billion years ago - Dark Energy - Something unknown is pushing the universe apart faster and faster - This mysterious force is called Dark Energy, making up \~70% of the universe\'s total energy Where do elements come from and which were first in our universe? - Big Bang (first few minutes): Hydrogen, Helium, and tiny amounts of Lithium formed - Stars (millions of years later): heavier elements like Carbon, Oxygen, and Iron formed through nuclear fusion - Supernova Explosions: created even heavier elements like gold and Uranium and spread them into space ------ Timing and theories regarding the formation of our galaxy, our solar system and Earth Process Theory Current view ------------------------ ----------------------------------------------- ------------------------------------------------- Galaxy Formation Monolithic Collapse & Hierarchical Clustering Milky Way formed by mergers of small galaxies Solar System Formation Nebular Hypothesis Dominant theory (disk collapse & accretion) Earth's Formation Accretion & Differentiation Proven by Earth's layering & radiometric dating - Nebular Hypothesis - The Solar System formed \~4.6 billion years ago from a cloud of gas and dust - Steps - 1\. Gravity pulled gas and dust together -\> rotating disk formed - 2\. Sun formed at center - 3\. Planets formed from leftover material Planets and their properties. General. - Terrestrial (rocky): Mercury, Venus, Earth, Mars - Gas Giants: Jupiter, Saturn - Ice Giants: Uranus, Neptune ------ Age of Earth - Earth is \~4.54 billion years old - Determined using radiometric dating of the oldest Earth rocks and meteorites Heat source - Accretional hear: from planetary formation - Radioactive decay: elements like Uranium release heat inside Earth - Core differentiation: heavy metals (iron and nickel) sank to form the core, releasing heat Chemical layers - Earth is divided into 3 main chemical layers based on composition - 1\. Crust (outermost layer) - Thin, solid layer made of silicates (Si, O, Al, Fe, Mg, Ca, Na, K) - Two types - Continental crust: thick (\~30-70 km), less dense, mostly granite - Oceanic crust: thin (\~5-10 km), more dense, mostly basalt - 2\. Mantle (middle layer) - Thicker than the crust (\~2,900 km) - Made of peridotite (rich in magnesium and iron silicates) - Solid but flows slowly due to heat (convection drives plate tectonics) - 3\. Core (innermost layer) - Iron (Fe) and Nickle (Ni) rich - Outer core: liquid (generates Earth's magnetic field) - Inner core: solid due to extreme pressure - The deeper you go, the denser and hotter the material Differentiation of Earth - When Earth was young, it was molten due to heat from accretion and radioactive decay - Heavy elements (iron and nickel) sank to form the core - Lighter materials (silicates) rose to form the mantle and crust - This separation process is called differentiation and explains Earth's layered structure Evolution of atmosphere(s) on Earth - Earth's atmosphere changed dramatically over time: - 1\. First atmosphere (\~4.6 billion years ago) - Mostly hydrogen and helium (lost to space) - Second atmosphere (\~4.0 billion years ago) - Formed from volcanic outgassing (CO~2~, H~2~O, N~2~, sulfur gases) - No free oxygen yet - 3\. Third atmosphere (\~2.5 billion years ago -- today) - Oxygen appeared due to photosynthesis by cyanobacteria (Great Oxygenation Event) - Modern composition: 78% N~2~, 21% O~2~, 1% other gases (CO~2~, Ar, etc) Bulk composition of Earth (elemental) - The bulk composition of Earth refers to the relative abundance of chemical elements that make up the planet. Scientists determine this composition by studying meteorites (which represent primitive solar system material), Earth's crust, mantle, and core, and seismic data - Most abundant elements in Earth (by Mass Percentage) Element Percentage by mass Main location ---------------- -------------------- --------------------------------------------- Iron (Fe) \~35% Mostly in the core Oxygen (O) \~30% Found in silicate minerals (crust & mantle) Silicon (Si) \~15% Major component of silicate rocks Magnesium (Mg) \~13% Abundant in the mantle Nickel (Ni) \~2.4% Found in the core (with Fe) Sulfur (S) \~1.9% Present in the core and mantle Calcium (Ca) \~1.1% Found in the crust and mantle minerals Aluminum (Al) \~1.1% Major component of continental crust - The core is mostly Iron and Nickel, making it Earth's densest later - The mantle is rich in Silicates (Si, O, Mg, Fe), forming minerals like olivine and pyroxene - The crust has a higher concentration of Aluminum and Calcium than the mantle and core - Evidence: - Meteorite studies -- certain meteorites (chondrites) are thought to be the same material that formed Earth, their composition matches what we expect for Earth's interior - Seismic data -- the way earthquake waves travel through Earth helps determine the density and composition of layers - Mantle & crust samples -- volcanic rocks bring up material from the mantle; surface rocks (crust) are directly analyzed Development of Earth's oceans: timing, source and evidence - Oceans formed \~3.8 billion years ago when temperatures cooled enough for water to condense - Sources of water - Volcanic outgassing -- released water vapor, which condensed into liquid water - Comet impacts -- brought additional water from space - Evidence: oldest sedimentary rocks (\~3.8 billion years old) show evidence of liquid water - Basically, oceans helped regulate Earth's climate and enabled life to develop First appearance of life - Earliest life (\~3.5 billion years ago) was microbial (bacteria-like) - Found in stromatolites (layered structures build by cyanobacteria) - These bacteria produced oxygen through photosynthesis, changing Earth's atmosphere forever ------ Population growth through time - Early humans (\~300,000 years ago) had slow population growth - The population exploded after the Industrial Revolution (\~1800s) due to advances in medicine, agriculture, and sanitation - 1 billion people in 1800 -\> 8 billion today Current population of Earth and carrying capacity - Earth's population is \~8 billion (2024) - Carrying capacity: the maximum number of people Earth can support, based on food, water, and energy availability - Estimates range from 9-12 billion depending on technological advancements - Key issue: overpopulation can lead to resource depletion and environmental stress ------ Earth's magnetic field & Van Allen belts - Generated by liquid iron flow in the outer core (geodynamo effect) - Protects Earth from solar wind and cosmic radiation - Van Allen Belts trap high-energy particles from the Sun, preventing radiation damage Current atmospheric composition Gas Percentage Role in atmosphere ---------------------- --------------------- ----------------------------------------------------------------- Nitrogen (N2) \~70.08% Stable gas, doesn't react easily. Provides atmospheric pressure Oxygen (O2) \~20.95% Essential for respiration and combustion Argon (Ar) \~0.93% Inert noble gas, result of radioactive decay Carbon dioxide (CO2) \~0.04% (400 ppm) Greenhouse gas, used in photosynthesis Neon (Ne) \~0.0018% Inert noble gas Helium (He) \~0.0005% Light gas, escapes Earth's gravity over time Methane (CH4) \~0.0002% (1.8 ppm) Potent greenhouse gas Water vapor (H2O) Varies (0-4%) Essential for weather, clouds, and precipitation - Nitrogen and oxygen dominate the atmosphere - CO2, Methane, and Water Vapor are critical for climate regulation - Trace gases (like Argon and Neon) don't react much but help determine Earth's past climate through ice core studies - How Earth's atmosphere formed - 1\. Early atmosphere (\~4.6 billion years ago) - Composed mainly of hydrogen and helium from the solar nebula - These gases were lost to space due to Earth's weak gravity and solar wind - 2\. Volcanic outgassing (\~4 billion years ago) - Volcanoes released CO2, H2O, N2, and sulfur gases - No free oxygen existed yet - 3\. Oxygen revolution (\~2.5 billion years ago) - Cyanobacteria (blue-green algae) started photosynthesizing, releasing O2 - This led to the Great Oxygenation Event, making life possible for more complex organisms - 4\. Modern atmosphere (\~500 million years ago -- today) - Oxygen levels stabilized - The balance of CO2 and O2 allows a habitable climate - Earth has a balanced atmosphere that supports life, unlike Venus (96% CO2, runaway greenhouse effect) or Mars (thin CO2 atmosphere) - The ozone layer (O3) protects life by absorbing harmful UV radiation Hypsometric curve - A graph showing the distribution of land elevation and ocean depth - 70% of Earth's surface is ocean, with an average depth of \~3.7 km Density and Composition of Core, Mantle and Crust. Layer Density (g/cm3) Composition -------- ----------------- ------------------------------------ Crust 2.7-3.0 Silicates (Si, O, Al, Fe, Mg) Mantle 3.3-5.7 Peridotite (Mg, Fe-rich silicates) Core 9-13 Fe and Ni - ------ Alfred Wegener's continental drift hypothesis - Alfred Wegener (1912) proposed that continents were once a supercontinent (Pangaea) and have since drifted apart Pangea, concept and timing - Pangaea was a supercontinent that existed during the late Paleozoic and early Mesozoic eras, assembling around 335 million years ago and breaking apart \~175 million years ago due to plate tectonics Event Time period ----------------------------- ---------------------------------------------- Formation of Pangaea begins \~335 million years ago (Late Carboniferous) Pangaea fully assembled \~300 million years ago (Early Permian) Breakup of Pangaea Begins \~175 million years ago (Jurassic) - Pangaea formed as smaller continents collided over millions of years due to convergent plate movement - It began to break apart during the Jurassic Period (\~175 million years ago), forming the continents we see today Lines of evidence supporting continental drift. - Fit of continents -- South America and Africa fit like puzzle pieces - Fossil evidence -- identical fossils found on different continents - Rock formations -- similar rock layers found on separated continents - Paleoclimate evidence -- ice sheets once covered areas that are now tropical Problems with continental drift - Wegener couldn't explain how continents moved - The mechanism was later explained by plate tectonics (seafloor spreading and convection) ------ Stress & types - Compression -- squeezing (convergent boundaries) - Tension -- stretching (divergent boundaries) - Shear -- sliding past each other (transform boundaries) Strain & types - Elastic -- rock returns to its original shape (temporary) - Ductile (Plastic) -- rock bends permanently - Brittle -- rock breaks (faulting) Plastic v rigid behavior - (high temp and pressure favor ductile behavior, while low temperature and pressure favor brittle behavior) - Rigid (brittle) behavior - The rock breaks or fractures instead of bending - Occurs at low temps and low pressure (shallow crust) - Leads to the formation of faults and fractures - Plastic (ductile) behavior - The rock bends or flows without breaking - Occurs at high temperatures and high pressure (deep in Earth's crust and mantle) - Leads to folding instead of fracturing Factors related to strain - Strain is the deformation (change in shape) or a rock due to applied stress - 1\. Temperature - High temp -\> ductile deformation (plastic flow) - Low temp -\> brittle deformation (fractures, faults) - 2\. Pressure - High pressure -\> rocks bend (ductile) - Low pressure -\> rocks break (brittle) - 3\. Strain rate (speed of deformation) - Fast deformation -\> brittle behavior (fracturing) - Slow deformation -\> ductile behavior (bending and stretching) - 4\. Rock type (composition & mineralogy) - Strong, rigid rocks (e.g. granite, basalt) -\> more brittle - Soft, ductile rocks (e.g. shale, limestone) -\> more likely to deform plastically - Summary Factor Brittle behavior Ductile behavior ------------- --------------------- --------------------- Temperature Low High Pressure Low High Strain rate Fast Slow Rock type Strong, rigid rocks Soft, ductile rocks ------ Lithosphere, details - The lithosphere is the cool, rigid outer shell of Earth, composed of the crust and uppermost mantle - It is broken into tectonic plates, which move due to mantle convection - Key characteristics - Depth: extends from the Earth's surface to \~100 km deep - Properties: strong, rigid, and brittle - Composition: includes both the crust (continental & oceanic) and the upper mantle - Movement: moves as tectonic plates that float on the asthenosphere Asthenosphere, details - The asthenosphere is a hot, weak, and partially molten layer of the upper mantle beneath the lithosphere - It flows slowly, allowing tectonic plates to move - Key characteristics - Depth: \~100 km to \~350 km deep - Properties: ductile rather than brittle - Temp and pressure: high enough to allow rock to flow but not completely melt - Convection currents: hot material rises, cool material sinks, driving plate movement - Lithosphere vs. Asthenosphere Property Lithosphere Asthenosphere ------------- -------------------------- ---------------------------------- Behavior Rigid, brittle Plastic, flows slowly Depth 0-100 km 100-350 km Movement Moves as tectonic plates Allows plates to move on top Composition Crust + uppermost mantle Upper mantle (hotter and weaker) Distribution of volcanoes and earthquakes - Earthquakes and volcanoes occur in specific patterns, mostly alone plate boundaries - Where they mostly occur - 1\. Along plate boundaries - At tectonic plate boundaries - 2\. At subduction zones (convergent boundaries) - Oceanic crust sinks into the mantle, melting and forming volcanoes - Creates volcanic arcs (e.g. Andes, Japan, Cascades) - Deep earthquakes occur in Benioff Zones (sloping zones of earthquakes near trenches) - 3\. At mid-ocean ridges (divergent boundaries) - New crust forms as plates pull apart - Volcanoes form along the rift zones (e.g. Mid-Atlantic Ridge) - Shallow earthquakes occur here - 4\. At transform boundaries - Plates slide past each other, creating strong earthquakes (e.g. San Andreas Fault) - No major volcanoes occur here - 5\. At hotspots (away from plate boundaries) - Mantle plumes can create volcanic islands (e.g. Hawaii, Yellowstone) - Earthquakes can happen due to volcanic activity but not because of plate movement Seafloor topography - Seafloor topography refers to the underwater landscape of the ocean floor - The ocean floor has mountains, valleys, ridges, and trenches shaped by plate tectonics - Major features of the seafloor Feature Description Example -------------------- ----------------------------------------------------------------------------------------- ------------------------------------------------------- Mid-ocean ridges Underwater mountain chains where new ocean crust forms at divergent boundaries Mid-Atlantic Ridge Deep-sea trenches Deep valleys where one plate subducts beneath another Mariana Trench (deepest point in ocean \~11 km deep) Abyssal plains Flat, deep-sea floor covered in sediment Large portions of the Atlantic & Pacific Ocean floors Seamounts & Guyots Underwater volcanoes (seamounts), some flattened at the top by erosion (guyots) Hawaiian seamount chain Continental shelf Shallow, gently sloping underwater edge of a continent East Coast of North America Rift valley A deep valley at the center of a mid-ocean ridge, where magma rises to create new crust Iceland (on the Mid-Atlantic Ridge) Fracture zones Large cracks perpendicular to ridges, caused by transform faults Mendocino Fracture Zone ------ Seafloor spreading - New crust forms at mid-ocean ridges and moves outward - Magnetic minerals record Earth's magnetic reversals, creating a symmetrical pattern Cross section of ocean, crossing a mid-ocean ridge - If you took a submarine from one side of the Atlantic Ocean to the other, you would pass through several distinct zones on the ocean floor (refer to *major features of the seafloor*) - New crust forms at mid-ocean ridges and spreads outward - Old crust is destroyed at deep-sea trenches Paleomagnetism and reversals (anomalies) - Paleomagnetism - Earth's magnetic field reverses every few hundred thousand to million years - When lava cools at mid-ocean ridges, magnetic minerals (like magnetite) align with the current magnetic field - This records the history of Earth's magnetic reversals in the ocean crust - How magnetic reversals create anomalies - When we look at the seafloor's magnetic pattern, we see symmetrical stripes on either side of mid-ocean ridges - These stripes flip between normal and reversed polarity, recording past magnetic field changes - This proves seafloor spreading is real and was a key piece of evidence for plate tectonics - Basically, - Alternating magnetic stripes on the ocean floor = proof that new crust is forming and spreading outward - Symmetry on both sides of ridges shows that seafloor spreading is continuous Age of ocean crust - The youngest ocean crust is found at mid-ocean ridges (where new crust forms) - The oldest ocean crust is found near deep-sea trenches (where it is subducted) - The oldest ocean crust is \~200 million years old, much younger than the continental crust (\~4 billion years old) - Why oceanic crust is younger than continental crust - Ocean crust is constantly recycled -- old crust gets subducted into the mantle, while new crust forms at ridges - Continental crust is permanent -- it does not get recycled in the same way - Basically, - Youngest ocean crust = at mid-ocean ridges - Oldest ocean crust = near trenches Plate movement rates - Plates move at speeds of \~1 to 10 cm per year (about the same speed as fingernail growth) - We measure movement using GPS, seafloor spreading rates, and magnetic striping - Fast vs. Slow spreading rates Type of ridge Spreading rate Example ----------------------- ---------------- -------------------- Fast-spreading ridges \>10 cm/year East Pacific Rise Slow-spreading ridges 1-5 cm/year Mid-Atlantic Ridge - Plates move at different speeds, but all follow the same seafloor spreading process Hotspots - Fixed mantle plumes create volcanic chains (Hawaii) Types of plates boundaries and examples - Divergent -- plates move apart (Mid-Atlantic Ridge) - Convergent -- plates collide (Andes Mountain) - Transform -- plates slide past (San Andreas Fault) Benioff zones - Deep earthquake zones at subduction boundaries (where oceanic crust sinks)