Origin of Earth s Water When Earth first formed it was so hot that the original water would be lost to space Water added later by comets and/or asteroids?? Some water (H 2 +O) formed in Protoplanetary disk, some water formed/originated in solar nebula
Internal Heat Heated mainly by impacts & radioactivity Protons determine element; Neutrons determine isotope. Unstable isotopes, decay into other elements with a certain half-life, producing heat Oldest rocks ~4.6billion yrs: Earth, Moon, Mars, Meteorites Heat depends volume-r 3 but radiated by surface-r 2 Small moons cool more quickly than big planets
Differentiation Crust of Earth less dense rock Mantle is plastic; 45%radius More dense iron sinks to core
Seismic Waves P-waves=Pressure speed 5km/sec S-waves=shear travel at 3km/sec Seismometer recording of Mexico earthquake Last earthquake felt in Victoria 11am 28Feb01 Time waves; find distance
Earth s Core Outer core: liquid Iron-shear waves not transmitted Inner core dense solid Iron
Plate Tectonics Crust and upper mantle form rigid lithosphere Broken into plates, which move about as fast as your finger nails grow Due to convection in Mantle
Plate Motions Convection in mantle causes midocean ridge = rift zones Youngest basalt rock near ridge compared to surrounding older rock shows magnetic reversals ~million year timescale Subduction Zones form stratovolcanoes = composite volcanoes
Magnetic Field Generated in Earth s Core Dynamo theory requires 1. Rotation of planet 2. Electrical conducting material 3. Convection/motion in core
Magnetosphere / Van Allen Belts Solar wind stopped at bow shock=magnetopause Protons trapped in lower belt; electrons higher belt Spiraling along magnetic field lines Apollo astronauts & IC s shielded from radiation
Aurora Borealis Caused by Solar Wind Guided by Earth s magnetic field Exciting air molecules Aurora=Northern lights from ISS Alaskan Aurora movie by A. Clay
Tides Moon s gravity causes tides Bay of Fundy has largest tides Victoria is the red dot We rotate into the high tidal bulge & then into the low tide area
Tidal Bulges All massive bodies exert gravitational forces Closer => stronger force Tides Forces result from unequal force on the near & far sides = differential gravitational force
Spring/Neap Tides Sun s tide is about half the moon s tide And can add= Spring or subtract=neaptide Depending on moon s phase Full 3 rd Quarter
Perigee & Apogee When the moon is closer to Earth, tidal force is stronger Higher high tides Lower low tides
Tides for Victoria Nominally two high & low tides_per day Coastline makes a big difference Bay of Fundy resonates ~13hrs Full Moon 3 rd ¼ Moon
Synchronous Lunar Rotation Earth raises tides on Moon with 20 times larger force Due to these tides Moon s rotation became locked to its orbital revolution Other moons & planets too
Tidal Bulge Pulls on Moon Tidal bulge accelerates moon which recedes 3.5 cm/year
Moon Pulls on Tidal Bulge so Earth s Rotation Slows From study of coral growth rings 600 Million years ago the year was 425 days long Each day is 0.0015 seconds longer than it was a century ago Last leap second was added at end of June 2012. Next 30Jun2015
Synchronous Earth Rotation In 10 Billion years Earth will rotate with one side always facing the moon 47 day month Like Pluto and Charon
During a Spring tide: a. The moon will be full or new phase b. The moon will be first or third quarter c. The sun will be near the vernal equinox d. The moon will be near apogee e. The sun will be near aphelion
To generate its magnetic field the Earth requires: a) Rapid rotation of the planet b) Electrically conducting core c) Convection of the core d) All of the above e) None of these the Earth s magnetic field is caused by a giant permanent magnet inside the Earth
Earth s Atmosphere Troposphere =lowest level = weather=convection Half atmosphere below 5km Stratosphere=ozone layer then Ionosphere
Ozone Layers Once enough O 2 in atmosphere ~2Billion years ago Ultraviolet light from Sun will form O 3 =ozone Which protects life on land from UV Ozone in stratosphere destroyed by CFC s from refrigerators etc. Leading to skin cancer etc.
Greenhouse Effect CO 2, Methane, Water all absorb infrared light so all are greenhouse gasses Earth is warmed by 30C More billions years ago when sun was young/fainter
Atmospheric Changes Primary Atmosphere might have been H2, He, CH4, NH3, H2O Secondary atmosphere outgassed probably H2O, CH4, CO2, N2 Now 20% O2 from photosynthesis by plants & after oxidizing iron
A Tsunami has nothing to do with a Tidal (Wave)
Comparative Planetology Earth is the standard for Terrestrial planets
Carbon Dioxide Cycle CO 2 dissolves in water Forms Carbonate rocks Which are subducted Volcanoes reemit CO 2 =Outgassing
Albedo=Whiteness More clouds = higher albedo and more cooling More Snow = higher albedo and more cooling Global temperature is critically dependent on albedo
CO 2 from burning fossil fuels causes global warming, But Global Warming
Snowball Earth 600 Million years ago continents at equator cooling Earth Ice formed to 30º latitude; Earth cools more Glaciers cover to the equator; cooling even more Volcanoes emit CO 2 increasing greenhouse effect; eventually warming
On to the Solar System
Origin of Biosphere Oldest fossils=stromatolites 3.5 Billion years ago Aquatic colonies of cyanobacteria Life started ASAP!
Early History of Earth Rocks from the Acasta River cliffs near Great Slave Lake dated to 4 billion years ago; so magma ocean frozen then Stages of planetary development: Differentiation, Impact Cratering, Flooding/Volcanism and Erosion
Ancient Human Modification of Climate CH 4 Solar Radiation A is the Solar radiation in the Northern hemisphere & Atmospheric Methane vrs age B is a blow up of the last 10,000 years Previous to 5,000 years ago methane was produced in swamps in Siberia But now it is produced in rice paddies Counteracting natural ice age trend? Solar Radiation CH 4 observed Natural trend CH 4
Carbon Cycle CO 2 dissolves in water Forms carbonate rocks Which are subducted Volcanoes remit CO 2
Earth s Three Energy Sources 1. Solar energy powers atmosphere & ocean motions 2. Tides of sun & moon help power ocean 3. Internal heat powers geological processes
Internal Heat Heated mainly by impacts & radioactivity Heat depends volume R 3 but radiated by surface R 2 All terrestrial planets have: 1. Core: Metallic: iron, nickel, iridium 2. Mantle: Iron rich, rocky 3. Crust: low density silicates