OCEAN STATS AND GEOGRAPHY OF THE BASINS

The Earth’s Water

Ocean Statistics

A. 70% of the Earth’s surface is covered by the oceans – hence the “water planet”

1. 2/3 of the Earth’s land masses are in the Northern hemisphere, which is 61% ocean

2. 80% of the Southern hemisphere is oceanB. 97% of all water is in the oceanC. 50% (or more) of the Earth’s

photosynthesis occurs in the oceansD. Average depth of the ocean is 4000 km or

2.5 milesE. Maximum depth of around 11,000 meters

– Mariana Trench

Geography of Ocean Basins

Traditionally classified into four large basins (doesn’t include Southern Ocean, listed in decreasing size).Pacific Ocean – largest and deepestAtlantic Ocean – growing ocean (Mid

Atlantic Ridge)Indian OceanArctic Ocean – northern hemisphereSouthern Ocean - continuous body of

water which surrounds the Antarctic continent below 60°S latitude.

THE CROSS SECTION VIEW

The Earth’s Layers

Earth’s Composition

Layers: Cross-Section of the Earth

Inner core – solid iron, intense pressure

Outer core - molten, rich in iron and magnesium - thought to generate the Earth’s magnetic field

Mantle - near the melting point, the mantle slowly swirls and mixes (Upper Mantle is found in both the Asthenosphere & Lithosphere)

Crust - outermost layer, solid, floats on the mantle, continental and ocean (Part of Lithosphere)

Proof of Layers

What evidence supports the idea that Earth has layers?

The behavior of seismic waves generated by earthquakes give scientists some of the best evidence about the structure of Earth. Wave speed depends on what is traveled through—if it can travel through that medium.

(above-left) S waves cannot penetrate Earth’s liquid core.

(above-right) P waves are bent as they pass through the liquid outer core.

Layering Terms

Density Stratification –Layering of earth based upon the density of the materials which it is made of.

Moho discontinuity –Boundary between crust and mantle. Identified due to changes in velocity as seismic waves as they move from one material to another

The Floating Layer

Where does the heat within Earth’s layers come from?

Heat from within Earth keeps the asthenosphere flowing. This allows the lithosphere to keep moving. The source of this heat is radioactive decay, given off when the nuclei of unstable forms of elements break apart.

This heat travels in convection currents in the mantle.

THE CRUST: OCEANIC AND CONTINENTALBUOYANCY AND ISOSTASY

The Top Layer

Oceanic versus Continental Crust

Oceanic crustal plates have a higher density and they are:

ThinnerGeologically younger than continental crustRich in iron and magnesiumBasalt, dark in colorLikely to sink

Oceanic versus Continental Crust

Continental crustal plates have a comparatively lower density and they are:

ThickerGeologically older than oceanic crustsRich in sodium, potassium, calcium, and

magnesiumGranite, lighter in color

Keeping the Crust AfloatBuoyancy - The tendency or capacity to remain afloat in a liquid or rise in air or gas

Isostasy (Isostatic Equilibrium) - Gravitational equilibrium between the Earth’s lithosphere and asthenosphere.

The ship sinks until it displaces a volume of water equal to the weight of the ship and its contents.

Floating Ships

Quiz Question: As a ship moves from salt to fresh water what happens to the ship?

Earth Rocks!!!

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