Title: Exploring the inner and outer shells of earth
1Exploring the inner and outer shells of earth
2Earth consists of a series of concentric layers
or spheres which differ in chemistry and physical
properties.
Chemical Layers
Physical Layers
3Physical state is determined by the combined
effects of pressure and temperature.
- Increasing pressure raises the melting point of a
material. - Increasing temperature provides additional energy
to the atoms and molecules of matter allowing
them to move farther apart, eventually causing
the material to melt. - Both pressure and temperature increase toward the
center of the Earth, but at variable rates.
4How do we learn about the inner structure of the
planet?
Seismic waves
5Seismology is the study of elastic waves that
travel through the earth Two main wave types
Compression waves (P-waves) travel by squeezing
and expanding medium they travel through. They
can travel through both solids and liquids (e.g.,
sound waves).
Shear waves (S-waves) travel by shearing
medium they pass through. S-waves can travel
only through solids since particles need to be
bonded to each other to propagate wave (similar
to a bull whip)
6Earthquake are an incredible source of seismic
waves
- Seismic waves travel along there quickest route,
generally through, the planetary interior to the
seismic stations, changing speed every time
material properties change.
7Reconstructing the internal structure of the
planet
solid
- Crust upper mantle large increases in seismic
velocities and density
solid, more dense
- Mantle Gradual velocity and density increase
Liquid Iron
- Outer core dramatic density increase and no
S-waves
- Inner core Jump in density and P-wave velocity,
S-waves return
solid Iron
Other planets?
8Earthquakes produce waves in the ocean
NOAA-GlobalOceanWave.mov
NOAA-IndianOceanWave.mov
9Earthquakes produce waves in the ocean
Sea level RISE FALL
Courtesy K. Satake, unpublished
10World Seismicity
Mw 6.0
Mw 7.7
Many large earthquakes occur along subduction
zones
Most Great earthquakes are subduction
mega-thrust events
11Major Research Programs in Geophysics
http//www.earthscope.org/
http//www.margins.wustl.edu/
http//www.neptune.washington.edu/
12The Physiography of the North Atlantic Ocean Floor
http//topex.ucsd.edu
continental margins
deep ocean basins
midoceanic ridges
13- Continental margins are the submerged edges of
the continents and consist of massive wedges of
sediment eroded from the land and deposited along
the continental edge. The continental margin can
be divided into three parts the Continental
shelf, the Continental slope, and the Continental
rise.
Continental Margin
14- Deep Ocean Province is between the continental
margins and the midoceanic ridge and includes a
variety of features from mountainous to flat
plains Abyssal plains, Abyssal hills, Seamounts,
and Deep sea trenches.
Deep Ocean Basin
15- Midoceanic Ridge Province consists of a
continuous submarine mountain range that covers
about one third of the ocean floor and extends
for about 60,000 km around the Earth.
Midocean Ridge
16WHY DO LAND AND OCEAN EXIST?
17Continents and ocean basins differ in
composition, elevation and physiographic features.
Geologic Differences between Continents and Ocean
Basins
2-3
- Elevation of Earths surface displays a bimodal
distribution with about 29 above sea level and
much of the remainder at a depth of 4 to 5
kilometers below sea level. - Continental crust is mainly composed of granite,
a light colored, lower density (2.7 gm/cm3)
igneous rock rich in aluminum, silicon and
oxygen. - Oceanic crust is composed of basalt, a dark
colored, higher density (2.9 gm/cm3) volcanic
rock rich in silicon, oxygen and magnesium.
18Geologic Differences between Continents and Ocean
Basins
19WHY DO LAND AND OCEAN EXIST?
OCEANIC CRUST THIN AND DENSER CONTINENTAL CRUST
THICK AND LITHER
20100 cm3 39 g
A
10 cm3 12 g
B
WATER
21100 cm3 39 g
A
WATER
22Apositively buoyant
100 cm3 39 g
Bnegatively buoyant
WATER
23100 m3 39 kg
A
10 m3 12 kg
B
WATER
24Isostasy refers to the balance of an object
floating upon a fluid medium. Height of the
mass above and below the surface of the medium is
controlled by the thickness of the mass and its
density (similar to ice floating in water).
25- Continents are thick (30 to 40 km), have low
density and rise high above the supporting mantle
rocks. - Sea floor is thin (4 to 10 km), has greater
density and does not rise as high above the
mantle.
Oceanic Crust Versus Continental Crust
26Three spheres surround the rocky portion of the
Earth.
- Hydrosphere includes all of the free water of
the Earth contained in the ocean, lakes, rivers,
snow, ice, water vapor and groundwater. - Atmosphere is the gaseous envelope that surrounds
the Earth and is mainly a mixture of nitrogen and
oxygen. - Biosphere refers to all living and non-living
organic matter.
27End of lecture
28Exploring the inner and outer shells of earth
NOAA-GlobalOceanWave.mov
NOAA-IndianOceanWave.mov
29Exploring the inner outer shells of earth
30(No Transcript)
31WHY DO WE CARE ABOUT THE GEOMORPHOLOGY OF THE
OCEAN FLOOR? (in the context of Oceanography)