ESC1011 Exam and Study Notes
Table of Contents Our Planet and its Place in the Universe The Fate of the Universe Where did everything come from? Formation of Solar Systems Extrasolar planets Rocky Planets the inner solar system Gas Giants the outer solar system Asteroids, the Oort Cloud and Kuiper Belt Internal Structure of the Earth Plate Tectonics when everything changed Our restless planet the oceans Our restless planet the continents The Earth s surface the rock cycle Mineral Groups Sedimentary Rocks Metamorphic Rocks and Metamorphic Processes Time and the Age of the Earth Fossils what are they, how do they form? Origins of life on Earth Pre-Cambrian Life single cells to complex life Life in the Palaeozoic (Cambrian) Life in the Mesozoic Dinosaurs in Australia Life in the Cenozoic the drying of Australia Geohazards and Plate Tectonics Earthquakes Volcanoes Landslides, Avalanches and Lahars Asteroids, meteors and meteorites Climate Change Natural Processes Climate Change Anthropogenic forces
Our Planet and its Place in the Universe Intro to the Earth and Earth Structure o The upper mantle is lower in density than the lower mantle o The internal structure of the earth is based on Observations of vibrations generated by earthquakes: their reflection, absorption and refraction Magnetic and physical properties of rocks and minerals, and their observed behaviour under extreme pressures and temperatures in laboratories Distribution of rocks and fossils found across the world Satellite observations of changing locations of continents since 1970 s o The internal structure, as we go down the list, density increases Continental crust (35km thick) Oceanic crust (10-15km thick) Upper mantle (solid rock) Lower mantle (solid liquid rock) The upper and lower mantle have convection currents, which means hot rises and cool drops Outer core (liquid iron liquid) Inner core (generates magnetic field solid)
The Fate of the Universe How did the Universe start? o Time began when the universe began o The Big Bang occurs (everything expands out from there) 10-35 seconds to 10-32 seconds Initial inflation of the Universe is exponential It is quark soup make up of protons and neutrons 10-30 seconds to 10-10 seconds Dark Matter created o Holds the structure of the universe together Matter dominates over Antimatter (Antimatter is the opposite charged particles of matter) 10-2 seconds 100 billion degrees Kelvin Super high density Photons (light), neutrinos and electrons are mixed with smaller numbers of protons and neutrons Three minutes and 46 seconds after 900 million degrees Kelvin Fusion of the nuclei of helium and hydrogen atoms The seeds of galaxies and other structures are formed and shaped by dark matter A bit later The universe cools down and gas condenses to form infant nebula and galaxies, inflation stops and expansion slows o Inflationary Era From the Big Bang to around 300,000 years, initial exponential acceleration, followed by slowing For the past 6 billion years, the Universe has started accelerating again, but at a much slower pace o The Dark Universe For the first 380,000 years after the Big Bang, no light as photons couldn t escape into the Universe The evidence to predict this has happened is the Afterglow of Creation which looks at background microwave radiation from the explosion predicted to be visible everywhere you look in space o The composition of the universe 70% Dark Energy 26% Dark Matter 4% Everything else (Stars, planets etc.) What is it now what is now anyway? o How old is the universe? Evidence from Ages of stars life cycles o Measures luminosity (brightness) of stars that burn H and He (main sequence stars) o Estimated to be around 8.5 billion years to 14.6 ± 1.7 billion years (minimum) Ages of stars radiometric dating o Some elements are radioactive and can be used for dating archaeological sites, rocks and the universe
Gas Giants the outer solar system Why are the planets further out gaseous and the planets closer to the sun more solid? o In the very early solar system, long before it was as we now see it, there were undoubtedly gaseous planets trying to form close to the newly-formed sun. At that time our sun blasted much more radiation into space than now, and that radiation literally destroyed the few gassy worlds near it. Only those planets that were more dense and contained metals, like Mercury, Venus, Earth, and Mars, could survive. o It is highly likely all planets have an iron-nickel core. Logically, all the light gases like hydrogen, and helium would be drawn away from the inner planets by the early suns huge gravity. The outer planets are far enough away to have kept their huge diverse atmospheres. If the suns ignition sequence 5 billion years ago was so powerful as to have stripped every last bit of our atmosphere back then, the earth would still be barren today. Jupiter (Io, Europa, Ganymede, Callisto and 63 others) o 317.828 x Earth mass o 10.9733 x Earth Radius o Average density = 0.241 x Earth o Massive atmosphere of H 2, He and traces of CH 4 o It does not have a solid surface, but may have a solid core about the size of Earth o Temperature at cloud tops = 125K o Great Red Spot Storm that has lasted at least 180 years but is shrinking Wind speeds up to 400kph Other storms appear and fade, but so far this one is still there o Moons Has 67 moons Four are large Io (Volcanoes) o Innermost moon o Size and density about the same as Luna o Radius 1821.6km o Trace atmosphere of SO 2 o Metallic Ni and Fe core o Silicate (partially molten) mantle and crust No significant difference in mantle and crust, although crust has more sulphur o Most volcanically active planet in solar system o 30x more active than earth o Hottest lava observed in solar system Europa (Icy ball, subsurface ocean, water vapour jets) o H 2 O-ice surface o No significant atmosphere o Light and dark linear features visible o No significant mountains o Few craters visible o Radius 1,560.8km o Ice is 20km thick o In 2012, the Hubble Telescope found Geysers of water at the poles It detected H and O ions escaping planet Evidence for liquid ocean under ice
Ganymede (Icy ball, lots of craters, subsurface ocean) o Bands of light and dark material across planet s surface o Heavily cratered surface o Internally generated magnetic field, so may have differentiated core o Subsurface ocean or ice? o Significant evidence of surface movement in past Callisto o Frozen surface o Subsurface ocean o Free O 2 in atmosphere Saturn (Titan, Iapetus, Rhea, Dione, Thethys, Minas, Enceladus and 55 others) o Gas Giant with complex ring system (mainly icy particles) o Rings held in place by smaller captured moons o Massive atmosphere of H 2 and He, traces of CH 4 o Temperature just within clouds are 134K o Moons Titan ( methanosphere hydrosphere of liquid methane) N 2 and methane atmosphere Complex carbon molecules making smog so we can t see through and need a radar to see its surface Ocean, lakes, rivers and rain of liquid methane Hyperion Enceladus (Geysers of liquid water from south pole ocean under ice) Resurfacing of about 60-70% of planet Not enough known yet to determine the source Has cold geysers Iapetus Uranus ( Titania, Oberon, Umbriel, Ariel, Miranda and 22 others) o Massive atmosphere of H 2, He and CH 4 o Mean temperature 59K o Rotates backwards on axis at massive tilt o Faint ring system and 27 moons o Moons Miranda (Ripped apart by tidal forces, or fragments of object that causes Uranus weird spin/tilt) Radius is 236km Composition if 50% rocky material and 50% water ice Striated and ridged surface, with massive troughs and scarps Origin of surface may have been to origin of horizontal axis of rotation of Uranus Jigsaw of linear and smooth terrain Origin of surface o Miranda has been completely shattered and reassembled several times in its history, each time burying some parts of the original surface and exposing some of the interior o Rifting and undercutting by upwelling and convection of partially molten ice Ejecta from the impact from whatever hit and changed Uranus s rotation pattern, or just the change in gravitational forces resulting from the rotation shift could have shattered Miranda