ORIGIN OF THE EARTH

Collapse of rotating cloud of interstellar dust and gas - as cloud collapsed, speed of rotation and heated by gravitational energy.

- material flattened into disk that became increasingly more dense - at center sun formed from self-sustaining nuclear reactions.

Left over gases and dust cooled and interacted forming grains and particles which eventually formed planets.

Protoearth may have formed like this 1000x diameter and 500x heavier than earth today. Heavier constituents moved towards core surrounded by lighter materials.

Sometime, sun started to shine - in addition to light energy, emitted electrically charged particles solar wind - which blew away gas that remained from 4 planets.

        - As protoearth warmed from solar radiation, H and He atmosphere boiled away.

Combination of solar wind and internal warming resulted in size.

As proton earth continued to contract, heat produced within planet by radioactivity increased. Earth may have become molten.

Origin of Atmosphere

Where did material that makes up present atmosphere and ocean come from?

- vulcanism - volcanic gases bubbling up from vapor mantle - atmosphere different from one earth had lost.

- contained little free O2, - mostly CO2, water vapor.

As earth cooled, clouds formed and most of the water vapor released from mantle stayed in atmoshere until earth cooled. Water condensed and accumulated in depressions on earth's irregular surface.

Source of H2O

CHEMICAL WEATHERING

As a result of weathering, elements contained in original crystalline rocks were dissolved and carried into ocean - also particulate matter - total mass of crystalline rock components freed by chemical weathering found as components of atmoshere, oceans or sediments.

EXCESS VOLATILES

Volcano activity presently producing these gases and venting them...large percentage recycled - dissolved in ground water...small percentage of volatiles are new gases released for the first time from crystalline rocks of the earth's crust.

-When molten magma cools, solid rocks form and some of the gaseous constituents of magma are freed - new volatiles coming to earth's surface.

Continuous degassing at the current rate over geologic time (i.e. past 3 by) - enough water vapor would have been produced to fill the ocean over 100 times.

Oceans filled gradually from degassing over geologic time.

Does continual degassing mean oceans will cover more move of earth's surface? Not necessarily

Volume in ocean basins directly related to difference in thickness between oceanic and continental crust....if we assume continental material has gradually accumulated, capacity of oceans basins could have increased along with volume of water produced. ocean basins also getting deeper.
 

OCEAN BASINS TODAY: PLANET EARTH OR PLANET OCEAN ?

A). 70.8% OF EARTH IS COVERED BY WATER Land not distributed evenly over globe - in Northern Hemisphere ratio of water to land = 1.5 /1 but in Southern Hemisphere ratio 4/1.

Continents separated by ocean basins connected to form a single body of water called the world ocean.

Distribution of ocean basins
Pacific - largest and deepest
Atlantic - 2nd largest but Indian Ocean deeper.