Earth’s Oceans Divisions of Ocean largest = Pacific half volume of Pacific = Atlantic 3 rd largest = Indian smallest = Arctic Southern = extends from Antarctica

How did Oceans form? when earth formed, no water about 4 billion years ago, earth cooled enough for water vapor to condense rains fell and filled deeper levels of the surface today’s oceans formed within last 300 million years

Characteristics of Ocean Water – Salinity salty; full of sodium chloride measure of the amount of dissolved salts in an amount of liquid higher salinity in areas with hotter, drier climates (higher evap rate)

Characteristics of Ocean Water (cont) higher salinity in slow moving water

Characteristics of Ocean Water (cont) temp decreases as depth increases

Water Cycle Evaporation Transpiration continuous movement of water ocean to atmosphere to land back to ocean change from liquid to gas caused by sun’s energy/heat evaporation from plant leaves

Condensation Precipitation water vapor cools high in atmosphere and changes back to liquid water forms clouds water particles cling to dust in air droplets become heavy enough to fall rain, snow, sleet, hail, etc…

Heat from Oceans absorb and hold energy from sun helps regulate temp in atmosphere

The Ocean Floor

Studying the Ocean Floor Sonar Sound Navigation and Ranging Sends out sound pulses from ships Bounces off bottom of the ocean Long return time = deep spot

Satellite Geosat Sends images from space Used to measure direction and speed of ocean currents Measure slight height changes of ocean’s surface Used to make detailed map of ocean floor

Revealing Ocean Floor Is Not Flat Continental Margin Two major regions: continental margin and deep-ocean basin Made of continental crust More shallow Contains – Continental Shelf – Continental Slope – Continental Rise

Deep-Ocean Basin Made of oceanic crust Deeper than continental margin Contains: – Abyssal Plain – Mid-ocean Ridges – Rift Valleys – Ocean Trenches These features develop near plate boundaries

Seamounts Underwater mountains of volcanic material If built up above sea level, becomes a volcanic island

Underwater Vessels Piloted Vessels Robotic Vessels Deep water exploration Piloted by people from within Ex: Alvin, Deep Flight Still controlled by people Can withstand more pressure Ex: Jason II and Medea