Marine Biology / Chapter 2 – The Sea Floor The Water Planet The Geography of the Ocean Basins

Traditionally classified into four large basins: The Pacific – deepest and largest The Atlantic Ocean The Indian Ocean The Arctic Ocean

Connected or marginal to main basins – shallow seas ie Mediterranean Sea, Gulf of Mexico, South China Sea.

The Structure of the Earth The external structure The internal structure

The Structure of the Earth Earth and solar system thought to have formed about 4.5 bya formed from debris left over from the “Big Bang” about 13.7 bya early forms entire planet probably molten allowed materials to settle in the planet according to their density

Substances of low density will float on substances o higher density. Density is the mass of a substance per unit volume Substances of low density will float on substances o higher density. Density = mass/volume

The Internal Structure reflects planets early beginnings materials sank according to density – formed concentric rings innermost layer – core pressure more than 1 million greater than surface temp. estimated to be more than 7200o F

Mantle – layer outside the core very hot; near rock melting point state of plastic – moves or swirls very slowly Crust is outer most layer Composition and character differ between oceanic and continental

oceanic crust is denser and consist of basalt continental crust less dense and consist mainly of granite Both are less dense than underlying mantle.

oceanic and Continental crust also differ in age. Oldest oceanic rocks are less than 200 million years old. Continental rocks can be as much as 3.8 billion years old.

Origin and structure of the ocean basins As early as 1620 – noted that coastlines of continents on opposite sides of the Atlantic fit together like pieces of a puzzle Cold deposits, geological formations, match up on opposite sides of the Atlantic Fossils on opposing coast also match

Alfred Wegner - 1912 – proposed first detailed hypothesis of continental drift Suggested single super continent he named Pangaea Proposed Pangaea began breaking the about 180 million years ago