Chapter 18 Ocean Motion Section 18-1 Ocean Water Notes Guide

Water Distrubution

Importance of Oceans  Oceans are important sources of food, energy, and minerals. -Energy sources such as oil, and natural gas are found beneath the ocean floor. - Copper and gold are mineral resources that are mined in shallow waters. - One-third of the world’s table salt is extracted from seawater by the process of evaporation. -Millions of tons of oil, coal, and grains are shipped over the oceans each year.

Origin of the Oceans  When the Earth was young, its surface was much more volcanically active than it is today.  When volcanoes erupt they give off lava, ash, water vapor, carbon dioxide, and other gases.  The water vapor was stored in Earth’s atmosphere, until it cooled enough to condense and into storm clouds.  Rains begin to fall, and the water filled low areas on the Earth called basins.  70 % of Earth’s surface is covered by ocean water.

Origin of Oceans

Composition of the Oceans  Ocean water contains dissolved gases such as oxygen, carbon dioxide, and nitrogen. -Oxygen is needed by organisms for respiration. -Oxygen enters the oceans from the atmosphere and from organisms that photosynthesize. -Carbon dioxide enters the ocean from the atmosphere and from organisms when they respire. -Nitrogen comes from the atmosphere.

Composition of the Oceans Continued…  Ocean water contains many dissolves salts. -Chloride and sodium are some of the ions in seawater. -These ions come from rocks that are dissolved slowly by rivers and groundwater and are carried to the ocean. -Erupting volcanoes add other ions.  Many other ions are dissolved in seawater.

Composition of Oceans Continued…  When seawater evaporates, the ions combine to form salts. -Sodium and chloride ions combine to form halite, which gives the ocean it’s salty taste. halite, which gives the ocean it’s salty taste. Salinity is the measure of amount of salts dissolved in seawater. - It is measures in grams of dissolved salts per kilogram of seawater. - One kilogram of seawater contains 35 g of dissolved salts or 3.5 percent. - This proportion has stayed constant for hundreds of millions of years.

Composition of Oceans

Removal of Elements  The ocean is in a steady state-elements are added to the oceans at the same rate that they are removed.  Dissolved salts precipitate out of ocean water and become part of the sediment.  Marine organisms use dissolved salts to make body parts. - Some remove calcium from the water to make bones. - Some use dissolved calcium to form shells, like oysters. -Calcium and silicon are removed more quickly from seawater than other elements.

Desalination  Salt can be removed from ocean water by the process of desalination.  As water evaporates, salt is left behind.  Scientists are working on technology to remove salt from seawater to make it drinkable.  Desalination plants use several methods to remove salt from the seawater to obtain freshwater for drinking.

Desalination