1. Exploring the inner and outer shells of earth

2. Chemical Layers Physical Layers
Earth consists of a series of concentric layers or spheres which differ in chemistry and physical properties.
Chemical
Layers
Physical
Layers

3. Physical 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.

4. How do we learn about the inner
structure of the planet?
Seismic waves

5. Seismology 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)

6. Earthquake 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.

7. Reconstructing the internal structure of the planet
Combining information from many seismic waves we can get a detailed internal structure of the earth.
Seismic Velocity and Density
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?

8. Earthquakes produce waves in the ocean
Sea level:
RISE
FALL
Courtesy: K. Satake, unpublished

9. World Seismicity Mw ≥ 6.0 Mw ≥ 7.7
( )
Mw ≥ 6.0
Mw ≥ 7.7
Many large earthquakes occur along subduction zones
Most “Great” earthquakes are subduction mega-thrust events

10. The Physiography of the North Atlantic Ocean Floor
continental
margins
deep ocean
basins
midoceanic
ridges

12. Type of continental margins

13. Passive Continental Margin
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.
Passive Continental Margin

14. Transport of sediments from the shelf to the continental rise

15. 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

16. 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

17. Hydrothermal Vents

18. 03_13a

19. WHY DO LAND AND OCEAN EXIST?

20. Geologic Differences between Continents and Ocean Basins
2-3
Continents and ocean basins differ in composition, elevation and physiographic features.
Elevation of Earth’s 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, igneous rock rich in aluminum, silicon and oxygen.
Oceanic crust is composed of basalt, a dark colored, higher density, volcanic rock rich in silicon, oxygen and magnesium.

21. Geologic Differences between Continents and Ocean Basins

22. WHY DO LAND AND OCEAN EXIST?
OCEANIC CRUST = THIN AND DENSER
CONTINENTAL CRUST = THICK AND LITHER

23. Oceanic Crust Versus Continental Crust
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

25. altimetry
Satellites in orbit around the planet use radar altimetry to measure the height of the sea level (accuracy of 2 cm).

27. Model of the shape of the Earth
geoid: The equipotential surface of the Earth's gravity field which best fits, in a least squares sense, global mean sea level (MSL)

28. Why ocean bathymetry?

29. Ocean Circulation and Climate
Heat Transport affected by topography!

30. Ocean Circulation and Climate
Ocean Currents take different paths!

31. Ocean Circulation and Climate
Deep ocean mixing and pathways

32. Ocean Circulation and Climate
Mixing energy and dissipation of tides!

33. Social impacts:
Tsunami

34. Social impacts:
Gas and oil extraction

35. Evidence of Global Warming in the Climate System:
Glacier melting
Kilimanjaro: ice caps are 80% gone since early 1900’s
All glaciers in tropics are melting rapidly
Impacts: water supply, power generation, tourism, local climate and ecology

37. Arctic - the most sensitive ecosystem?
Arctic sea ice has shrunk by 1 million sq km and thinned from 3.1m to 1.8m average
More freshwater, reduced ability to travel over ice
All summer ice gone in this century
Ecological consequences huge!

38. Arctic warming 1979 2003 Sea ice melting Warming temperature
Key feedback! (animation)
Reduces albedo (reflectivity) of earth, allowing more radiation to be absorbed
Warming temperature
Melts permafrost
Ice sheet stability? Key sea level question!
Rate of warming 8x faster in last 20 years than in last 100
1979
2003

39. Arctic ecosystems impacts
Reduced ice: less algal production under ice = undermines base of food chain
Seal pups emerge just when ice is melting - earlier melt means they are exposed before ready to thrive
Caribou need ice to island-hop; they are falling through as ice thins
Polar bears hunt on ice in winter, retreat to land in summer. Less ice forces them onto land earlier

40. Higher sea level… As water warms, it expands (“thermal expansion”).
Glaciers are melting
Observation: 3mm/yr in past few decades
Prediction: ~0.5m rise by the end of this century, 2-4m in 500 years
This will have a major impact on
Developed coastal regions
Low-lying island nations
Intensity of coastal flooding during storm surges
Coastal ecosystems (e.g. mangroves, estuaries)

41. More intense storms…
Hurricanes get their energy and staying power from warm water in the tropical oceans.
As waters get warmer, we expect that hurricanes will become more intense.
Significant change not yet observed.

42. Oceanography and Climate - millenial timescales
Vertical circulation of the ocean
MOVIE:
The Day After Tomorrow

43. Oceanography and Climate
Climate changes are defined to occur on different space and time scales.
What makes it interesting is that processes happening on different temporal and spatial scales are not separable and interact with each other  COMPLEXITY and NONLINEARITY
WHY?
The ocean has a very long memory.
We will learn about this, and about the mechnism of interaction between ocean-atmosphere-land-ecosystems.