Transcript ppt
The Material Earth Solar System Accretion Theory Accreted components Chondrite –composition roughly equal to that of the Earth. This is a slab of NWA 2089 (LL3) Anatomy of a chondrite www.arizonaskiesmeteorites.com CAI’s: Calcium Aluminum-rich inclusions, varying size of material that condensed at T> 1100ºC Chondrules: rounded grains rich in silicon, condensed between 400-900 ºC. Matrix: low temperature silicon and carbon rich phases, condensed below 175 ºC. Chondrites become attracted and attach Growth continues with impacts - heating, rounding with size When a body is larger than 100 km diameter and hot, iron and other heavy compounds sink towards center, silicon-oxygen compounds float towards surface. Hot Earth Initial bombardment formation of Earth; impact energy transferred into heat Contraction due to increasing gravitational force; compression increases heat Radioactive decay of elements produces energies that heat surroundings The earth’s heat results from kinetic (movement) energy: the energy of large (impactors) and small (electromagnetic photons and atomic particles) objects. But space is cold - we are losing this heat You should know: •It’s built from chondrites. •Center half is largely made of iron. •Only the outer core is mostly liquid •Outer half is largely made of oxygen and silicon. •Our knowledge diminishes as we move into the planet. How do we learn of our planet’s interior? Journey to the Center? KTB Kola Photo by Hans-Joachim Kümpel Heat release moves crustalupper mantle masses. Surface includes once deeply buried rocks The Adirondacks Old rocks from the middle continental crust Volcanoes - heat and mass breach the surface Mantle fragment diamond Mid Ocean ridge Our understanding of the earth falls off with depth. 6,378 km Piston Cylinder Solid Media Pressure Apparatus Faking it - reproducing conditions within a lab setting. Near isostatic pressure and elevated temperatures Earthquake (seismic) waves are the result of energy transfer through matter An earthquake releases the energy accumulated from stress in the crust of the earth Seismic shadow Figure 19.16 19-378 The speed of the waves changes with depth This is a function of material behavior reflecting changes in three things: •Temperature •Pressure •Composition The major plates of the lithosphere Source:After W. Hamilton, U.S. Geological Survey Cold Lithosphere will sink. Slab drags plate downward. Volcanism and rupturing at weak points builds new oceanic crust A deeper mechanism driving it all? Subduction: Continental Arcs Example: the Cascades Trenches are the deepest part of the oceans Divergent Boundary - Continental Rift Example: the East African Rift NASA Digital Tectonic Activity Map Magmas generated by mantle melting can make their way to the surface. They also may induce partial melting in the crust. NASA STS32 Continental collision Example: the Himalaya Arbuckle Mountains, Oklahoma Rattlesnake Mountain, Wyoming The hydrologic cycle 2-458 Water appears to be the most crucial compound to life on Earth It merits a closer look: H-O bonds are bent towards each other. Hydrogen atoms near one end lend a positive charge. Examples of very porous rocks Rocks like these are responsible for storage and transports of large reservoirs of potable water. Sandstones, white area are grains of quartz (SiO2), blue area is a dye to show pore space in rock) The path of groundwater •4.56 billion year old chondrite-derived planet •Differentiation has resulted in an iron core, a rocky mantle and crust, a hydrosphere, and an atmosphere. •Heat loss from its formation drives interior and surface modification through plate tectonics. •Heat gain from Sun’s fusion reaction drives surface modification through hydrologic cycles. •The change of these energies results in very complicated systems.