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Earth. The Dynamic Planet. Earth’s Interior. Courtesy of the USGS. Core. The core is differentiated into an inner solid region and an outer liquid region. Both regions are composed mostly of iron and nickel Inner core is not solidly tied to rest of Earth, and is free to rotate.

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Earth

Earth

The Dynamic Planet


Earth s interior

Earth’s Interior

Courtesy of the USGS


Earth

Core

The core is differentiated into an innersolid region and an outer liquid region.Both regions are composed mostly ofiron and nickelInner core is not solidly tied to rest ofEarth, and is free to rotate

Diagram from USGS

Earth’s magnetic field created by electrically conductive fluidflowing past magnetic field, which creates an electric current;

current strengthens the magnetic field


Mantle

Mantle

Mantle is composed mostly of siliconThought to exhibit a plastic behavior; solid on short time scales, liquid over long timescales

Diagram from the USGS

Differences in temperature between core and crust cause mantle to convect; this convection drives movement at the surface


Crust

Crust

Crust is mostly SiO2Two types of crust: oceanic and continental crustOceanic crust is thinner and denser; darker in color;basaltic (only about 50% silicate)

Continental crust is thicker and less dense; lighter in color;granitic (about 70-80% silicate)

Diagram from USGS


Seismology

Seismology

Surface waves - Travel along the Earth’s surface, do not penetrate the crust, slowest wave speed

Compressional body waves - particles move in direction of wave velocity, fastest wave speed;

called P-waves

Transverse body waves - particles move perpendicular tothe direction of wave velocity, slower than compressional,but faster than surface; also called

shear waves since the particles will

experience a shearing action;called S-waves


Seismology cont

Seismology, cont.

Use earthquakes to probe theinterior of the EarthWaves travelling through the

Earth are refracted (bent) and reflected depending upon theirproperties and those of the different layers of the Earth

S-Wave shadow zone


Plate tectonics

Plate Tectonics

Originally conceived of as continental

drift by Wegener; he noticed similarities

in coastlines, fossil record, rock layers,

and glacial scarring

Modern satellite technology

allows us to measure the

relative movement of the plates


Plate boundaries

Plate Boundaries

Divergent - Plates move apart from each

other

Convergent - Plates move toward each

other

Transform - Plates move parallel to the

boundary in opposite directions


Divergent plate boundaries

Divergent Plate Boundaries

  • Start as rift valleys

  • Basaltic, high density magma wells up from the mantle-crust interface to replace rock

  • New crust that forms is thinner and denser; as it cools, it sinks lower than the surrounding continental crust

  • Ocean water eventually fills in between the two continents


Convergent plate boundaries

Convergent Plate Boundaries

If oceanic crust collides withcontinental crust, oceanic crust goesunder (subduction zone), melts, andresurfaces as an island arcEx. New Zealand, Aleutian Islands

If two continental plates collide,

crustal material “piles up” and

a mountain chain is developed

Ex. Himalayan Mountains


Transform plate boundary

Transform Plate Boundary

As plates move past one another,

friction causes sides to stick together

While sides are stuck, stress builds

between the plates

When stress gets high enough, sides

violently slide past one another

Photograph by Robert E. Wallace, USGS

Loma Prieta Earthquake, 1989, Courtesy of the USGS


Rock types

Rock Types

Constant plate movement drives the rock cycle

Three different types of rock are igneous, metamorphic, and

sedimentary


Igneous

Igneous

Rock formed

from a molten

state

Type of igneous rock determined by 1) type of magma from

which rock cools and 2) location where rock cools

Volcanic - extrusive; magma cooled at the surface; smaller crystals

Plutonic - intrusive; magma cooled below the surface; larger crystals


Sedimentary

Sedimentary

Formed from sediment that

is cemented together

Type of rock depends upon

1) size of sediment and

2) origin of sediment

Photo of Canyonlands National Monument by Pratte

Two Types

Clastic - broken rock and mineral that are cemented together

Ex.: sandstone, shale, conglomerate

Chemical - minerals that precipitate out of solution

Ex.: limestone, chalk


Metamorphic

Metamorphic

Formed from other rocks by

changing mineralogy or texture

without passing through a molten

state

  • Change occurs because of one or more of the following

  • parameters:

  • pressure - causes rock crystals to change orientation and structure (Ex. gneiss)

  • temperature - induces different chemical bonds without melting(Ex. hornfels)

  • chemically reactive fluid - minerals in the fluid replace mineralsin the rock (Ex. petrified wood) or form new bonds


Rock cycle

Rock Cycle

Processes like weathering,

erosion, and plate tectonics

change the rock from one

form to another

Rock can be transmuted from

any form to any other form’

by these processes

Example: An igneous rock that is brought to the Earth’s surface is

weathered and eroded. Sediment pile is buried, causing cementation

into a sedimentary rock. Further burial creates pressures strong

enough to change chemical bonds, creating a metamorphic rock.


Soil types

Soil Types

Soil - a mixture of organic andinorganic sediments found on the

Earth’s surface; comprised of

different layers

O horizon - consists of decomposing organic matter; might be missing

A horizon - comprised of a mixture of organic and inorganic matter

E horizon - light colored, acidic layer found in evergreen forests

B horizon - brown or red layer enriched in clay, iron, and/or aluminum

K horizon - enriched with calcium carbonate; found in arid regions

C horizon - lowest layer comprised almost entirely of inorganic rock sediment


Soil forming factors

Soil Forming Factors

Different horizons

occur at different

locations for many

reasons

Some factors:

  • Climate - temperature, precipitation, and wind affect weathering,erosion, vegetation, and decomposition of organic matter

  • Local rock - provides the inorganic material for soil

  • Topography - steeper slopes mean more erosion

  • Vegetation - holds soil in place; provides the organic material for soil

  • Time - more mature soils have had elements working on it longer

  • Mankind - our activities affect erosion and soil nutrients


Weathering and erosion

Weathering and Erosion

Weathering - the breaking apart of rocks either physically orchemically

Erosion - the removal of sediment from a location; can occur by water, wind, landslide, etc.; enhanced by mankind’s disturbances


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