The Material Earth. Solar System Accretion Theory.
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Transcript of The Material Earth. Solar System Accretion Theory.
Chondrite –composition roughly equal to that of the Earth. This is a slab of NWA 2089 (LL3)
www.arizonaskiesmeteorites.comAnatomy of a chondrite
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.
Accreted components
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.
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
Hot EarthHot Earth
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?
Heat release moves crustal-upper mantle masses. Surface includes once deeply buried rocks
Heat release moves crustal-upper mantle masses. Surface includes once deeply buried rocks
The Adirondacks
Old rocks from the middle continental crust
Our understanding of the Our understanding of the earth falls off with depth.earth falls off with depth.
6,378 km
Mid Oceanridge
Piston CylinderPiston CylinderSolid Media Pressure ApparatusSolid Media Pressure ApparatusPiston CylinderPiston CylinderSolid Media Pressure ApparatusSolid Media Pressure Apparatus
Faking it - reproducing conditions within a lab setting.
Near isostatic pressure and elevated temperatures
An earthquake releases the energy accumulated from stress in the crust of the earth
Earthquake (seismic) waves are the result of energy transfer through matter
The speed of the waves changes with depth
This is a function of material behavior reflecting changes in three things:
•Temperature
•Pressure
•Composition
Source:After W. Hamilton, U.S. Geological Survey
The major plates of the lithosphere
The major plates of the lithosphere
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 ArcsSubduction: Continental Arcs
Example: the Cascades
Trenches are the deepest part of the oceans
Divergent Boundary - Continental RiftDivergent Boundary - Continental Rift
NASA STS-32Example: the East
African Rift
NA
SA
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Magmas generated by mantle melting can make their way to the surface. They also may induce partial melting in the crust.
H-O bonds are bent towards each other. Hydrogen atoms near one end lend a positive charge.
H-O bonds are bent towards each other. Hydrogen atoms near one end lend a positive charge.
Water appears to be the most crucial compound to life on Earth
It merits a closer look:
Water appears to be the most crucial compound to life on Earth
It merits a closer look:
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)
•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.
•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.