The Material EarthThe 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?

KTB

Photo by Hans-Joachim Kümpel

Kola

Journey to the Center?Journey to the Center?

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

Volcanoes - heat and mass breach the surface

diamond

Mantlefragment

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

19-378Figure 19.16

Seismic shadowSeismic shadow

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

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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.

Continental collisionContinental collision

Example: the Himalaya

Arbuckle Mountains, Oklahoma

Rattlesnake Mountain, Wyoming

The hydrologic cycleThe hydrologic cycle

2-458

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)

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.

•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.