EARTH ( ) Structure of the Earth Deep Wells: - deepest is 12 km (7.5 miles) in Russia - temp at bottom = 190oC or 375oF! Seismology - science of shock waves - caused by earthquakes, volcanoes, etc. - shows density and boundary of regions Two basic types of seismic waves: Shear (S) waves: - material displaced side-to-side Radius:(R) 6.378 x 106 m 3924 miles (1 R ) Mass:(M) 5.98 x 1024 kg (1 M ) Mean Density:( ) 5.5 g/cm3 Unique Features: LIFE Pressure (P) waves: - material is compressed - can travel through any material - need a solid, will not go through a liquid RESULTS: Crust: low density rock (2.5-3.5 g/cm3) variable thickness (5 50 km) rigid, brittle material Mantle: high density rock (3.5-5 g/cm3) 2900 km thick plastic - hot, solid but can flow Outer Core: liquid Iron (some Nickel) very high density (9-11 g/cm3) 2200 km thick Inner Core: solid material; (~ 13 g/cm3 ) crystallized iron-nickel?? Differentiation - mixing material with different densities -lower density objects will "float" -higher density objects will "sink" - Ice floats on water - Rock floats on liquid iron
Formation of Earth: -accretion/collisions of smaller objects -great amounts of heat released -original Earth molten - Cause of many geographic features - mountain ranges, oceanic trenches and rifts, island chains Earth became differentiated: -densest elements "sink" to center -iron, nickel -lightest elements "rise" to surface -silicon, oxygen compounds Today, slowly cooling off: Interior of Earth still very hot at center (> 5300 oc or 9600 of!) Surface of Earth Crust of Earth is broken into plates: - 15 major plates move ~ 10 cm/yr - carried by gradual motion in mantle Plate Tectonics - cause of many active features - volcanoes, earthquakes Plate Tectonics in the past http://www.scotese.com/earth.htm
Other processes that affect surface -Erosion, Deposition (from wind, water) -Life (Human activities) Mississippi Delta -Impact Cratering http://www.passc.net/earthimpactdatabase/index.html Tswaing Crater, South Africa Earth s Surface is geologically "young" - only 10-100 million years old Atmosphere Composition: Nitrogen (N2) 78.09% Oxygen (O2) 20.95% Argon (Ar) 0.93% Carbon Dioxide (CO2) 0.035% (rising) Water Vapor (H2O) varies ( 0.4%) But, atmospheres of Venus and Mars CO2 = 95% - 96%!! Where is all the CO 2 on Earth?? Why is there so much N 2, O 2, H 2 O on Earth?? Recycled Air Earth s atm. has changed since formation Action of Volcanoes: - Outgassing -water vapor, N2, CO2, Ar - Primary source of Earth's Water -water is predominant surface
Action of water, rain: - dissolves CO2, settles into rocks -Examples: Limestone Coca-Cola, Pepsi Action of Plant Life: (algae) - releases O2, absorbs CO2 http://www.nasa.gov/vision/universe/newworlds/ets_breath.html Environmental Issues Ozone (O3) Depletion Ground Level Ozone - near surface - pollutant (crop & respiratory problems) Ozone Layer-in middle layer (10-35 km high) - absorbs and blocks UV from sun Depletion of Ozone Layer - manmade Chloroflourocarbons (CFC) - reacts with and destroys O3 The Ozone Hole - sharp drop in ozone over South Pole - hole is dramatically larger since 1980 Effects of Ozone Depletion (increase UV) - can induce skin cancer, cataracts, affect plants, animals
2006: Tied record - largest ozone hole Set record - least amount of ozone http://ozonewatch.gsfc.nasa.gov/ 2015 2018 Montreal Protocol, 1987 (ratified by 191 countries) " Perhaps the single most successful international agreement to date has been the Montreal Protocol. " Kofi Annan, Former Secretary General of the United Nations - phaseout of CFC by 1995 in developed countries - total phaseout of other compounds by 2015 - but CFC takes years to reach O 3 layer - CFC levels in stratosphere reducing very slowly. - full recovery not expected until year 2050 2070
The Greenhouse Effect What is it? Refers to energy (heat) gained versus energy (heat) lost Primary energy source for Earth SUN - most of Sun's energy is in the form of visible light - atmosphere is transparent to visible Light Earth s surface absorbs most of the energy - heats up and reradiates energy - emits infrared (IR) energy Atmosphere is not transparent to IR - greenhouse gases absorb IR, heat up - slows down heat loss to space - "greenhouse effect" does not generate heat - like a blanket slows heat loss from Body Greenhouse Gases: - H 2 O, CO 2, Ozone (O 3 ), methane (CH 4 ), nitrous oxide (N 2 O) - avg T of Earth is 35 o C (63 o F) warmer than it would be with no atmosphere. - avg T of Earth = 60 o F But, all forms of combustion release CO2 - CO2 levels are highest in 800,000 yrs - June 2018, level hit 411.09 ppm Consequences: Global Temperature Rise: 8 warmest yrs on record all 2005-2017 Hottest year ever: 2016 2 nd hottest year: 2015 3 rd hottest year: 2017 42 years since a colder than average year (1976) https://www.co2.earth/co2-ice-core-data
Shrinking ice sheets: Antarctica: -127 billion tons ice per year Greenland: -286 billion tons ice per year https://climate.nasa.gov/vital-signs/ice-sheets/ Sea level rise: - rose 6.7 inches in 20 th century - rose 1.3 inches from 2000-2010 - rose 0.7 inches from 2010-2017 - rising 0.13 inches every year, accelerating https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-level Changes of Ocean chemistry: Oceans becoming more acidic as more CO 2 absorbed (+30% in past 100 yrs) https://www.pmel.noaa.gov/co2/story/what+is+ocean+acidification%3f 30 indicators of climate: All show long term trend to warmer climate https://www.epa.gov/sites/production/files/2016-08/documents/climate_indicators_2016.pdf Paris Climate Agreement (2015) - global action plan to limit global warming to less than 1.5 o C - ratified by 195 countries - U.S. announced withdrawal in 2017