1 HNRS 228 Astrobiology Chapter 4 - Earth - Bennett & Shostak Lecture Notes for Chapter 4 6 and 11 February 2014 Dr. H. Geller 2 The Habitability of Earth zGeology and Life (4.1) zReconstructing the History of Earth and Life (4.2) yRocks, radiometric dating, geological record, fossils, geological time scale, Earths age zThe Hadean Earth and the Dawn of Life (4.3) yAtmosphere, oceans, heavy bombardments zGeology and Habitability (4.4) yEarths interior, plate tectonics, magnetosphere 3 The Habitability of Earth zClimate Regulation and Change (4.5) yGreenhouse effect, carbon cycle, ice ages, Snowball Earth, long term habitability zThe Process of Science in Action: Formation of the Moon (4.6) ySister model, capture model, spinoff model 4 Some Guiding Questions 1.What is the greenhouse effect? How does it affect the average temperature of the Earth? 2.Is the Earth completely solid inside? How can scientists tell? 3.How is it possible for entire continents to move across the face of the Earth? 4.How does our planets magnetic field protect life on Earth? 5.Why is Earth the only planet with an oxygen-rich atmosphere? 6.Why are prevailing winds generally from the west over most of North America but generally from the east in Hawaii? 7.What are global warming and the ozone hole? Why should they concern us? 5 Telling Rocks Apart zHow geologists tell apart different minerals and rocks ycolor, luster, texture yhardness test xscratching one against another diamond is hardest yacid test xusing weak hydrochloric acid to ystreak test xform a streak across a ceramic tile 6 zPlate tectonics is involved in the formation of the three major categories of rocks yIgneous Rock xcooled from molten material ySedimentary Rock xLayered eroded material formed by the action of wind, water, or ice yMetamorphic Rock xRock that has been altered in the solid state by extreme heat and pressure 7 The Rock Cycle 8 iClicker Question Rocks formed from other rocks that are heated and placed under great pressures are called Aigneous rocks Bsedimentary rocks Cmetamorphic rocks Dfault rocks Escarp rocks 9 iClicker Question Rocks formed from layers of fine material that have been compressed under water are called Aigneous rocks Bsedimentary rocks Cmetamorphic rocks Dfault rocks Escarp rocks 10 iClicker Question Rocks formed when molten material cools and solidifies are called Aigneous rocks Bsedimentary rocks Cmetamorphic rocks Dfault rocks Escarp rocks 11 iClicker Question Which of the following are not used to identify rocks: Acrystalline shape Bacid test Cstreak test Dhardness test Eall of the above can be used to identify a rock 12 Surface Building Processes zStress ystress is a force that tends to compress, pull apart, or deform ydifferent types of stress xcompressive stress xtensional stress xshear stress zStrain ythe adjustment to stress 13 Stress and Strain 14 Surface Building Processes zFolds ybends in layered bedrock zAnticline/\ zSyncline \/ 15 Surface Building Processes zFaulting yformation of a crack caused by relative movement of rock on either side of a fracture 16 Mountains zelevated parts of the Earths crust that rise abruptly above the surrounding surface zCauses yfolding, faulting, volcanic activity 17 Volcanoes zhill or mountain formed by the extrusion of lava or rock fragments from magma below zDifferent types yshield, cinder cone, composite (composite shown) 18 Tear-Down Processes zWeathering ymechanical weathering ychemical weathering zErosion ymass movement (mass wasting) yrunning water (floodplain, delta) yglacier ywind (deflation and abrasion) yimpact cratering 19 Earthquakes zDefined as quaking, shaking, vibrating, or upheaval of the ground zEarthquake causes yelastic rebound theory zIntensity measure yRichter Magnitude xnot linear scale 20 iClicker Question What is the term used to specifically define a downward fold of rock material? Ascarp Beroda Cfold Dsyncline Eanticline 21 Earths Interior and How We Know It 22 Earths Inside Story Energy transfer in the mantle similar to that of a pot of boiling water. 23 Earths Interior, Then and Now 24 What We Learn from Seismometers zThe Earths inner and outer cores are composed of iron with some nickel and other metals mixed in zThe mantle is composed of iron- rich minerals zBoth temperature and pressure steadily increase with depth inside the Earth 25 Crustal Rumblings 26 iClicker Question Which of the diagram represents the MANTLE of the Earth? A B C D ENone of the above. 27 iClicker Question Which of the diagrammed sections of the Earth's interior represents the Outer Core? A B C D ENone of the above. 28 iClicker Question Which of the diagrammed sections of the Earth represents the CRUST? A B C D ENone of the above. 29 iClicker Question Energy transport from one region to another by the movement of material as in the mantle of the Earth is known as Achaos. Bradiance. Cconduction. Ddifferentiation. Econvection. 30 iClicker Question The existence of earthquake shadow zones indicates that there is an abrupt change between the properties of the mantle and those of the core. Specifically, the transverse wave shadow zone shows that the outer core must be Asolid. Bliquid or semi-liquid. Cgaseous. Dsimilar to crustal material. Eimpossible to determine. 31 Plate Tectonics zThe theory that the Earths crust is made of rigid plates that float on the asthenosphere. zConsider the scientific evidence for plate tectonics and what forced scientists to accept the theory as fact 32 Plate tectonics, or movement of the plates, is driven by convection within the asthenosphere zMolten material wells up at oceanic rifts, producing seafloor spreading, and is returned to the asthenosphere in subduction zones zAs one end of a plate is subducted back into the asthenosphere, it helps to pull the rest of the plate along 33 Plate Tectonics zThe Earths crust and a small part of its upper mantle form a rigid layer called the lithosphere. zThe lithosphere is divided into huge plates that move about over the plastic layer called the asthenosphere in the upper mantle 34 Fossils across an ocean 35 The continents appear to fit together like a jigsaw puzzle 36 Development of Geologic Time zFossilization zReading the Rocks yprinciple of uniformity yprinciple of original horizontality yprinciple of superposition yprinciple of crosscutting relationships yprinciple of faunal succession yradiometric dating zGeologic Time Scale 37 Geologic Time Scale 38 Earths Atmosphere zComposition yNitrogen (78%), Oxygen (21%), Argon, Water Vapor, CO 2, Methane, other zAtmospheric Pressure ypressure exerted by atmosphere zWarming ySun - solar constant is not really constant ygreenhouse effect xwarming due to the transparency of a substance to radiation at visible wavelengths and opacity to infrared radiation 39 The Earths atmosphere has changed substantially over time zThe Earths atmosphere differs from those of the other terrestrial planets in its chemical composition, circulation pattern, and temperature profile zThe Earths atmosphere changed from being mostly water vapor to being rich in carbon dioxide zA strong greenhouse effect kept the Earth warm enough for water to remain liquid and to permit the evolution of life 40 The appearance of photosynthetic living organisms led to our present atmospheric composition, about four- fifths nitrogen and one-fifth oxygen 41 Structure of the Atmosphere 42 Circulation in our atmosphere results from convection and the Earths rotation Because of the Earths rapid rotation, the circulation in its atmosphere is complex, with three circulation cells in each hemisphere 43 Winds zLocal winds ywind chill factor zGlobal wind patterns 44 Weather Producers zAir Masses zEvaporation yAbsolute humidity yRelative humidity zFronts zWaves and cyclones zStorms ythunderstorms, tornadoes, hurricanes 45 An idealized cold front 46 An idealized warm front 47 Weather Forecasting zPredictions based upon ycharacteristics, location, and rate of movement of air masses and associated fronts and pressure systems yComplex computer models zLed to science of chaos ychaotic dynamic systems 48 Climate zgeneral pattern of the weather that occurs for a region over a number of years zMajor climate regions ytropical ytemperate ypolar 49 The principal climate zones 50 iClicker Question Which of the following layers of the atmosphere is highest above the surface of the Earth? Atroposphere. Bstratosphere. Cthermosphere. Dmesosphere. Eozone layer. 51 iClicker Question What is the primary ingredient of the Earth's atmosphere? ANitrogen BOxygen CNitrogen and oxygen in equal parts DHydrogen ECarbon dioxide 52 iClicker Question In what part of the atmosphere does weather occur? Ahydrosphere Bstratosphere Cionosphere Dtroposphere Eall of the above 53 iClicker Question How rapidly a planet loses its atmosphere depends on the planet's zI.mass zII.atmospheric composition zIII.temperature zIV.rotation period AI & II BIII & IV CI, II, & III DII, III, & IV EI, II, III, & IV 54 iClicker Question Earth possesses few visible craters and the Moon possesses many. This is largely because AEarth formed later than the Moon and, therefore hasn't encountered as many meteoroids. Bthe Moon doesn't have an atmosphere that could burn up meteorites before impacting. Cerosion and plate tectonics have slowly removed evidence of past cratering on Earth. DA, B and C. EOnly B and C above. 55 Ocean currents influence temperatures and climates 56 The hydrologic cycle Tidal forces help power the motion of the oceans 57 Distribution of the Water 58 Watersheds of three rivers 59 The path of groundwater 60 Oceanography zWaves and tides ychanges coastal structure xtransport of material ylong term and short term changes zA Climate control mechanism yocean conveyor belt xmajor control of climate 61 A wave passing in the open ocean 62 A wave becoming breaking onshore 63 Ocean Conveyor Belt - Major Climate Control 64 The Earths Magnetic Field zElectric currents in the liquid outer core generate a dipole magnetic field ySimilar to a coil of wire around an iron nail zThis magnetic field produces a magnetosphere that surrounds the Earth and blocks the solar wind from hitting the atmosphere zTraps particles from the solar wind in regions yProducing Van Allen Belts zMost of the particles of the solar wind are deflected around the Earth by the magnetosphere. 65 A bow-shaped shock wave, where the supersonic solar wind is abruptly slowed to subsonic speeds, marks the outer boundary of the magnetosphere 66 An increased flow of charged particles from the Sun can overload the Van Allen belts and cascade toward the Earth, producing aurorae Some charged particles from the solar wind are trapped in two huge, doughnut-shaped rings called the Van Allen belts 67 iClicker Question The presence of Earths magnetic field is a good indication that Athere is a large amount of magnetic material buried near the North Pole. Bthere is a quantity of liquid metal swirling around in the Earth's core. Cthe Earth is composed largely of iron. Dthe Earth is completely solid. Ethere are condensed gasses in the core of the Earth. 68 Energy Sources and the Earths atmosphere, oceans, and surface 69 The Greenhouse Effect zSolar energy is the energy source for the atmosphere zIn the greenhouse effect, some of this energy is trapped by infrared absorbing gases in the atmosphere, raising the Earths surface temperature above what it would be if there was no greenhouse effect 70 71 Rising Carbon Dioxide 72 Industrial chemicals released into the atmosphere have damaged the ozone layer in the stratosphere 73 iClicker Question The greenhouse effect occurs largely because Aa gas is transparent to visible light and opaque to infrared radiation. Ba gas is transparent to infrared radiation and opaque to ultraviolet radiation. Cozone is transparent to ultraviolet radiation and opaque to infrared radiation. Dmethane is transparent to infrared radiation and opaque to visible light. Ethe sun emits more infrared radiation than ultraviolet radiation.