Earth_in_Context

Earth_in_Context - Chapter 1: The Earth in Context...

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Unformatted text preview: Chapter 1: The Earth in Context --Universe --Solar System --Stars & Galaxies --Doppler Effect / Red Shift >> Big Bang Earth’s Structure and Composition EARTH 2 - Dr. Sabina Thomas Cosmology Humans seek to explain our surroundings. Humans Where do we come from? Where do we fit in the Universe? Why are we here? When will this class be over? Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Cosmology Study of the structure and history of the Universe Cosmology even more so than Geology requires thinking Cosmology in unfamiliar scales of space and time. Spatial scales. Spatial Attometers (10-21 meters), to 10s of billions of light years (9.4622 meters +). Temporal scales. Attoseconds (10-21 seconds), to 10s of billions of years (3.1517 seconds +). Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Earth’s Changing Place 3,000 years ago, humans knew the heavens well: They knew that stars were fixed relative to other stars They knew that stars moved predictably across the sky They did not think of Earth as a planet, however Movement in the heavens was attributed to deities The ancients thought the Universe was geocentric Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context GREEK GEEKS Aristotle (384 – 322 B.C.E.)-- Father of western science science Four elements: Earth, Water, Air, Fire Crystal spheres in the sky on which heavenly Crystal bodies circled around a motionless central Earth bodies A heliocentric (sun-centered) universe was heliocentric proposed by the Greeks ~ 250 B.C.E. but had received no support received Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Greek Geeks Ptolemy (100–170 C.E.) “proved” the Ptolemy geocentric universe geocentric The idea held as religious dogma The for 1,400 years (thank you, Aristotle) for Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context One of my favorite geeks: Eratosthenes of Cyrene/ Syene (c. 275­192 B.C.E.): mathematician, geographer, astronomer, social theorist, historian, scholar, librarian in Alexandria. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Renaissance >> Enlightenment Copernicus (1473-1543) • Heliocentric theory • Circular orbits • De Revolutionibus (published in 1543) Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context What‘s up with that nose? Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Tycho Brahe (1546 – 1601) 1572 – A bright new star in the sky 1577 – Plotted a comet’s path Kepler (1571-1630) Studied Brahe’s data and came up with the laws of planetary motion – Kepler’s Laws Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Observed: Spots on the sun Mountains on the moon The phases of Venus Moons orbiting Jupiter WHO IS IT? Galileo (1564-1642) Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Newton (1643 – 1727) Published the Principia Contained Basic laws of motion The universal law of gravity F = G M1 x M2 d2 F = Force of Gravity M = mass d = distance Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Recap – The Renaissance… Rebirth of rational thought in 15th century Europe. Spawned a new age of scientific discovery. Copernicus – Published evidence for heliocentricity. Kepler – His elliptical planetary orbits refuted Ptolemy. Galileo – Observed moons orbiting Jupiter. Galileo Newton – Planet motion explained by his Theory of Gravity. Natural laws governed natural events. Geocentricity faded away. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context The Big Picture: Stars and Galaxies Stars are immense balls of incandescent gas. Light and heat derives from nuclear fusion reactions. Gravity binds stars together into vast galaxies. The solar system is on an arm of the Milky Way galaxy. Our sun is one of 300 billion Our stars in the Milky Way. stars You are HERE! Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Stars and Galaxies The Andromeda galaxy is 2.2 million light years away. The speed of light (c) is 186,000 miles/s. The Moon is 1.3 light seconds (~237,000 miles) away. The Sun is 8.3 light minutes (~93 million miles) away. The Universe contains more than a 100 billion galaxies. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Questions How did the Universe form? Do galaxies move with respect to each other? Is the Universe expanding? Contracting? How do we know anything about these matters? The Doppler Effect permits us to detect star motion. The Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context What’s next is a bit complicated … Team Assignment coming up! Topic for Question of the Day: Topic Question “The Universe Is Expanding How do we know?” Deadline: Wednesday June 29th Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context The Doppler Effect Waves compress or expand with relative motion. Waves The stopped train sounds the same to Anna and Bill. The moving train sounds different to Anna and Bill. Anna hears a higher pitch from compressed sound waves. Anna Bill hears a lower pitch from expanded sound waves. As the train passes Anna, the pitch drops (higher to lower). As This is commonly heard as cars whiz by on a road. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Electromagnetic Spectrum Visible wavelengths range from 400 and 700 nanometers. 400 nm – Blue = Higher frequency. 700 nm – Red = Lower frequency. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Spectral Lines – Stellar Fingerprints Absorption and Emission Lines Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Doppler Effect applied to Light: The Red Shift A moving star displays Doppler shifted light (spectral lines) moving Moving light waves compress (blue) or expand (red) Approaching starlight is compressed (blue) Receding starlight is expanded (red) Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context The Expanding Universe Light from galaxies was seen to be “red shifted.” Light Hubble recognized the red shift as a Doppler Effect. Hubble He concluded galaxies were moving away at great speed. He Curiously, no galaxies were found heading toward Earth. The Expanding Universe Theory evolved. The TIME Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Big Bang An expanding Universe? “When did it all begin?” The Big Bang: All mass and energy in a single point. It exploded ~13.7 Ga, and has been expanding ever since. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context The Big Bang During 1st instant, only energy – no matter – present. Started as a rapid cascade of events. 1. 2. 3. 3. 4. 5. Formation of protons and neutrons Light elements formed (He, Be, Li, B) Light The Universe expanded, cooled, and decreased in density Simple molecules formed Atoms and molecules coalesced Atoms into gaseous nebulae into Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context After the Big Bang Gravity caused collapse of gaseous nebulae. Collapse resulted in increases in temperature, Collapse density, rate of rotation density, Condensed nebulae form first stars that burn off their Condensed fuel (H, He) quickly fuel As a results, they Collapse and heat up Produce heavy elements Explode catastrophically Explode (supernova) (supernova) Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Solar System Formation The Nebular Theory. A 3rd, 4th or nth generation nebula forms ~4.56 Ga. Hydrogen and Helium left over from the big bang. Heavier elements produced by stellar nucleosynthesis. This material coalesces into an accretion disc Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Solar System Formation The ball at the center grows dense and hot. Fusion reactions begin; the Sun is born. Dust in the rings condenses into particles. Particles coalesce to form planetesimals. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Solar System Formation Planetesimals accumulate into a larger mass. An irregularly-shaped proto-Earth develops. • The interior heats up and becomes soft. • Gravity shapes the Earth into a sphere. • Chapter 1: mantle. The interior differentiates into a-Fe core and rocky The Earth in Context Essentials of Geology, 3rd edition, by Stephen Marshak Solar System Formation Soon, a small planetoid collides with Earth. Debris forms a ring around the Earth. The debris coalesces and forms the Moon. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Solar System Formation The atmosphere develops from volcanic gases. When the Earth becomes cool enough. Moisture condenses and accumulates. The oceans are born. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Solar System Formation Synopsis Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context The Solar System Solar system: A sun, planets, moons and other objects. Earth shares the solar system with 7 planets. A planet… Is a large solid body orbiting a star (the Sun). Has a nearly spherical shape. Has cleared it’s neighborhood of other objects. Moon – A solid body locked in orbit around a planet. The solar system also includes asteroids and comets. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context The Planets Two groups of planets occur in the solar system. Terrestrial (Earth-like) – Small, dense, rocky planets. Mercury, Venus, Earth, and Mars. Jovian (Jupiter-like) – Large, low density, gas-giant planets. Jupiter, Saturn, Uranus, and Neptune. Pluto is no longer considered to be a planet. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context The Solar System The Terrestrial planets are the 4 most interior. The Jovian planets occupy the 4 outermost orbits. The asteroid belt lies between Mars and Jupiter. Planet orbital planes lie within 3o of the Sun's equator. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Earth What would solar system visitors notice about Earth? What A magnetic field. An atmosphere. Surface features. Continents Oceans Polar ice caps Evidence of humanity? Evidence of intelligent life? Evidence Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context In other words … The Earth Has It All: Atmosphere Hydrosphere Cryosphere Geosphere Biosphere See if you can match them up Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Our Star … The Sun ejects matter into space as the Solar Wind: Magnetically charged particles. Stream outward in all directions. Stream Consists of… Protons (+ charge). Electrons (– charge). A small percentage of the Solar Wind hits Earth. small Luckily, Earth has a dipolar Luckily, magnetic field that forms a shield around Earth (the magnetosphere) (the Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context The Van Allen Belts The solar wind is deflected by the magnetosphere. Near Earth, the stronger magnetic field forms the Van Allen belts, which arrest deadly cosmic radiation. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Aurorae Some ions escape Van Allen belts. Pulled to the magnetic poles, the ions generate light. Spectacular aurora follow solar flares. Aurora borealis – Northern lights. Aurora australis – Southern lights. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context The Atmosphere Densest at sea-level, the atmosphere thins upward. The atmosphere is mostly nitrogen (N2). Oxygen was absent from the atmosphere before 2.5 Ga. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context The Atmosphere 99% of atmosphere is below 50 km. The rest is between 50 and 500 km. Sea-level atmospheric P = 14.7 psi. Essentials of Geology, 3rd edition, by Stephen Marshak Lowermost layer is the Troposphere Lowermost (0-11 km) (0-11 Where weather takes place Leave rest up to meteorologists and Leave climatologists climatologists Chapter 1: The Earth in Context Surface Features Continents are high; oceans are low, as a result of Continents differing buoyancy/density of each type of crust. differing density Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Elemental Composition 90% percent of Earth is comprised of 4 elements: (“FeOSiMg”): (“FeOSiMg”): Iron (Fe) – 35% Oxygen (O) – 30% Silicon (Si) – 15% Magnesium (Mg) – 10% Magnesium Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Earth Materials Minerals – Rocks – Metals – Inorganic solids Minerals Minerals make up most of the rocks and, hence, most of Minerals the earth. the Most minerals on Earth are silicates (based on Si and O). Most silicates (based Organic chemicals – Carbon containing compounds. Biological remains (wood, peat, lignite, coal, and oil). Biological Geologically rare (decompose in contact with oxygen). Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context A Layered Earth We live in the atmosphere and on the thin outer skin of We in on Earth. Earth. We now know that Earth is comprised of layers. The Crust. The Mantle. The Core. (You will see that it’s more complicated than that) Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Earth’s Interior Layers Crust Mantle Continental Continental Oceanic Upper Lower Core Outer - Liquid Inner – Solid Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context © W. W. Norton A Layered Earth Seismic waves permit analysis of the interior. Seismic Wave velocity changes with density. Velocity changes give depth of layer changes. Velocity Seismic ray Wave front An earthquake sends out waves in all directions. Sandstone Peridotite Seismic waves travel at different velocities in different rock types. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Fig. D.2c,d S-wave Solid Liquid P-wave Both P-waves and S-waves can travel through a solid, but only P-waves can travel through a liquid. Solid iron alloy P-wave Molten iron alloy P-waves travel faster in solid iron allow than in liquid, such as molten iron alloy. The propagation ofby Stephen Marshak waves — 2. Essentials of Geology, 3 edition, earthquake rd Chapter 1: The Earth in Context © 2009 W.W. Norton P-wave Fig. D.3a,b Refraction and reflection of waves Incoming light Air Water Reflected Refracted A ray of light reflects and refracts when it crosses the boundary between different materials. Slower Slower Faster A ray entering slower material bends away from the boundary, but a ray entering faster material bends toward the boundary. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context © 2009 W.W. Norton Faster Fig. D.6a,b,c Seismic ray Focus In a stack of discrete layers, rays bend at each boundary. Mantle If velocity increases gradually with depth, rays curve smoothly. The velocity of seismic waves changes with depth in the mantle . Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context © 2009 W.W. Norton The velocity of seismic waves increases with depth in the mantle, so rays curve. Fig. D.7a Focu s 103° P-wave shadow zone P-wave shadow zone 143° P-waves do not arrive in the P-wave shadow zone. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context © 2009 W.W. Norton P-wave shadow zone Fig. D.7b Focu s 103° S-wave shadow zone S-wave shadow zone S-waves do not arrive in the S-wave shadow zone. Shadow zonesedition, bythe discovery of the Earth's core — 2. and Stephen Marshak Essentials of Geology, 3 rd Chapter 1: The Earth in Context © 2009 W.W. Norton 103° Fig. D.5 P-wave velocity (km/s) 7 9 5 11 0 Lithosphere LVZ 200 Upper Mantle 400 Depth (km) Transition zone 600 Lower mantle 1000 The velocity ofedition, by Stephenin the mantle changes with depth. P-waves Marshak Essentials of Geology, 3 rd Chapter 1: The Earth in Context © 2009 W.W. Norton 800 Fig. D.7c Source Seismograph Incident ray Mantle Reflected ray Outer core Seismic waves reflect off the inner core-outer core boundary. Shadow zonesedition, bythe discovery of the Earth's core — 3. and Stephen Marshak Essentials of Geology, 3 rd Chapter 1: The Earth in Context © 2009 W.W. Norton Inner core Fig. D.8 0 0 4 Velocity (km/s) 8 12 400 670 S-wave P-wave Inner coreouter core boundary 6371 The velocity-versus-depth profile of the Earth. Essentials of Geology, 3 edition, by Stephen Marshak rd Chapter 1: The Earth in Context © 2009 W.W. Norton Core-mantle boundary 4155 Depth (km) 2900 Fig. D.9a Mantle Inner core Outer core Faster Tomographic image of the whole Earth. Tomographic3 images of the Earth's interior — 1. Essentials of Geology, edition, by Stephen Marshak rd Chapter 1: The Earth in Context © 2009 W.W. Norton Slower Fig. D.9b,c Plate graveyard North America Pacific Ocean 660 km Convecting cell Mantle plume Lower Mantle Tomographic3 images of the Earth's interior — 2. Essentials of Geology, edition, by Stephen Marshak rd Modern view of the Earth's complex and dynamic interior. Chapter 1: The Earth in Context © 2009 W.W. Norton Close-up tomographic image of the mantle. Fig. D.10a,b Ground surface A seismic-reflection profile. Color stripes are subsurface layers. Essentials of Geology, 3rd edition, by Stephen Marshak 100 ft 1000 ft Chapter 1: The Earth in Context © 2009 W.W. Norton Trucks thump the ground to generate a seismic signal. Fig. BXD.1.1 Geoid high The Earth's geoid is distorted by highs and lows in the gravity field. An exaggerated representation of the geoid. Essentials of Geology, 3 edition, by Stephen Marshak rd Chapter 1: The Earth in Context © 2009 W.W. Norton Geoid low Earth’s Layers Physical Geology - Dr. Sabine Thomas INTERNAL STRUCTURE OF THE EARTH Layers of Differing Composition Layers of Differing Physical Properties Depth C R U S T (continental / oceanic) -------------------------------- Lithosphere ----------------“Moho” ______Lithospheric Mantle__________________ 100 km M A N T L E Low-Velocity Zone (Part of Asthenosphere) 400 km UPPER MANTLE Transition Zone -------------------------------------------------------------------600 km LOWER MANTLE _______________________________________ CORE Outer Core ----------------------------- Inner Core _______________________________________ Essentials of Geology, 3rd edition, by Stephen Marshak 2,900 km 5,155 km 6,371 km Chapter 1: The Earth in Context The Crust The outermost “skin” of Earth with variable thickness. Thickest under mountain ranges (70 km - 40 miles). Thinnest under mid-ocean ridges (3 km – 2 miles). Mohorovicic discontinuity (“Moho”) at base of the crust. The “Moho” separates the crust from the upper mantle. The Andrija Mohorovičić found this change in P-wave velocity. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Two Types of Crust Two Continental crust – Granitic, underlies the continents. Average rock density about 2.7 g/cm3. Average thickness 35–40 km. Oceanic crust – Basaltic, underlies the ocean basins. Density about 3.0 g/cm3. Average thickness 7–10 km. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Earth’s Mantle Earth’s Solid rock layer between the crust and the core. Solid 2,885 km thick, the mantle is 82% of Earth’s volume. 2,885 Mantle composition is the ultramafic rock peridotite. Below ~100–150 km, the rock is hot enough to flow. Below Hot mantle rises, cold mantle sinks (convection). Hot Three subdivisions: Upper, transitional, and Lower. Three Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context The Core An iron-rich sphere with a radius of 3,471 km. An 2 components with differing seismic wave behavior. Outer core Liquid iron-nickel-sulfur 2255 km thick. Density – 10-12 g/cm3 Inner core Inner Solid iron-nickel alloy. Radius of 1220 km. Density – 13 g/cm3. Flow in the outer core Flow generates the magnetic field. generates Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context ¡ Lithosphere – Asthenosphere ! Lithosphere – The outermost 100–150 km of Earth. Non-flowing, rigid material that moves as tectonic plates. Non-flowing, Made of 2 components: Crust and Upper Mantle. Made Asthenosphere – Upper mantle below lithosphere. Asthenosphere below Shallow under oceans; deep under continents (“root”). Flows as a soft solid (plastic, or ductile). or ductile). Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 1: The Earth in Context Earth’s Layers Physical Geology - Dr. Sabine Thomas INTERNAL STRUCTURE OF THE EARTH Layers of Differing Composition Layers of Differing Physical Properties Depth C R U S T (continental / oceanic) -------------------------------- Lithosphere ----------------“Moho” ______Lithospheric Mantle__________________ 100 km M A N T L E Low-Velocity Zone (Part of Asthenosphere) 400 km UPPER MANTLE Transition Zone -------------------------------------------------------------------600 km LOWER MANTLE _______________________________________ CORE Outer Core ----------------------------- Inner Core _______________________________________ Essentials of Geology, 3rd edition, by Stephen Marshak 2,900 km 5,155 km 6,371 km Chapter 1: The Earth in Context ...
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This note was uploaded on 02/25/2012 for the course EARTH 2 taught by Professor Thomas during the Summer '11 term at UCSB.

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