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Origins of the oceans. Where did the water come from?. Just as scientist wondered how the land masses of earth formed and you studied last semester
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Where did the water come from? • Just as scientist wondered how the land masses of earth formed and you studied last semester • Scientist also wonder how the earth’s oceans are formed; less than 1.7 billion years ago, carbon dating rocks showing first signs of higher levels of iron oxidation
2 competing theories • Oxygen, carbon, nitrogen and hydrogen are unlocked from earth’s matrix of elements through outgasing during earth’s creation. As earth’s surface temperature cools molecules lose energy and cannot escape earth’s gravitational force and an atmosphere is formed. It is believed earth had enough elements stored in reservoir to supply all the water molecules needed for the oceans and atmosphere.
Billions of years after Earth’s creation, many impacts with space debris brings enough water vapor to earth. Water locked in meteorites are released when it crashes into the earth and the water vapor cannot escape earth’s gravity.
Deep Impact image of Comet Tempel 1 prior to July 4, 2005 collision; verifies ice made of water exists on the surface of comets www.networlddirectory.com/.../March-4-2006.html
Common factors • In both theories, the earth is in the ideal position to retain water for oceans and atmosphere. Just the right distance from the sun to keep water in its liquid form • Earth is not too cold and not too hot *too cold and all liquid would freeze just as moons around Jupiter and Saturn, or planets like Neptune and Uranus
*too hot and atoms and molecules can have enough energy to overcome earth’s gravity and radiate into space. • Earth has just the right mass (size) for gravity, temperature, and atmospheric pressure to act on water molecules
Chapter 10-4 Ocean Currents
Current – stream of water flowing in the oceans http://www.uwsp.edu/geo/faculty/ritter/images/maps/ocean_currents_small.jpg
Coriolis effect – bending of Earth’s wind and ocean currents by Earth’s rotation http://www.kidsgeo.com/images/coriolis-effect.gif
Density current – stream of water that moves up and down in ocean depths • Factors that increase density • Water temperature – warm water rises and cooler water sinks • Evaporation in tropical zones increases salinity • Removal of water in the form of ice at the poles increases salinity
Chapter 10-5 Ocean Waves
Wave – regular up and down movement of water • How are waves created • Wind blows along surface of water • Length of time and fetch determine how large the waves will be • Fetch – area of wind effect http://www.seafriends.org.nz/oceano/ocean11.gif
Crest – highest point of a wave • Trough - lowest point of a wave • Wavelength – the distance between two successive crests • Period – the time between two successive crests http://www.seafriends.org.nz/oceano/ocean11.gif
Wave energy technology http://earthsci.org/mineral/energy/wavpwr/wfigure_4.jpg
Chapter 10-6 14-5 Ocean Tides
Tide – regular change in the level of Earth’s oceans due to the sun’s and moon’s gravitational forces • Flood tide – incoming or rising tide • Ebb tide – outgoing or falling tide • Spring tide – tide that is higher or lower than a normal tide • Neap tide – tide that is not as high or as low as a normal tide
