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 Contraction due to Radioactive decay of formation of Earth; increasing gravitational elements produces impact energy force; compression energies that heat transferred into heat increases 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 crustal- upper 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 Magmas generated by mantle melting can make their way to the surface. They also may induce partial melting in the crust. NASA Digital Tectonic Activity Map NASA STS- Example: the East African 32 Rift
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 (SiO 2 ), 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.
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