2. ◦ 70-71% of Earth’s crust covered by ocean water ◦ 4 Major Oceans  Pacific – largest and deepest  Atlantic- little larger than the Indian  Indian – same depth as Atlantic, but smaller  Arctic – smallest and shallowest

3. How is the ocean the largest source of fresh water?

4. ◦ Ocean water: a mixture of dissolved gases and solids in pure water ◦ Contains 85 of 90 naturally existing elements ◦ 96.5% pure water; 3.5% dissolved minerals

5. ◦ Salinity – amount of dissolved salts in ocean water  expressed in ppt (parts per thousand)  # of grams of salts dissolved in 1 kg of ocean water

6. ◦ Sources of minerals - (NaCl the most common)  Volcanic activity  Erosion from land (upstream)  Waves breaking on the land

7.  Precipitation, runoff, and melting sea ice and icebergs - result in lower salinity  Formation of sea-ice and evaporation – result in higher salinity

8.  N, CO 2, and O  Amount varies with depth – cold water holds more gases  Oxygen/ CO 2 cycle between plants and animals same as on land