Fresh and Saltwater Systems Topic 4: The Oceans

Ocean Water is Salty 1 Kg of sea water contains 35 g of dissolved salts. This works out to 3.5% of ocean water being salts. Salinity is a measure of how much salt is dissolved in water. Eg. Dead Sea. Salinity also measure in parts per trillion (PPT). Where does the salt come from? Freshwater rivers and streams move salts and earth into the sea making ocean salty.

The Ocean Floor Oceans make up the largest ecosystems on Earth, however, they’re so deep we cannot see beyond 100 m. To map the ocean floor scientists use technologies such as radar and sonar that allow them to ‘see’ the floor. They’ve discovered underwater mountain ranges called ocean ridges and valleys called ocean trenches.

The formation of the ocean basins is due to the movement of tectonic plates.

Continental Shelf Is the submerged part of a continent and stretches out km from the shoreline. At the end of the shelf the land drops down at a steep angle to meet up with the ocean floor. The part of the shelf that slopes down is called the Continental Slope. The ocean floor is also called the abyssal plain.

Ocean Waves Waves are a disturbance which transmits energy from one point to another. Waves are caused by winds or tsunamis. The stronger the disturbance, the larger the wave amplitude. Water travels in a circular motion in a wave, but does not actually move from its position. Storms that produce strong waves are called storm swells.

Tsunamis Are massive tidal waves caused by underground earthquakes or volcanic eruptions. Major tsunamis occur every years and can kill thousands. A tsunami which began off the coast of Indonesia killed up to 230’000 people in A graphic of the 2004 Tsunami

Breakers Waves that make it all the way and break or collapse on the shore are called breakers. These are the waves that surfers ride on. HW: Worksheet questions. Use the notes and text-book.

How Waves Change Shorelines The force of waves crashing against a shoreline causes the shape of the shoreline to change as erosion takes place. The angle that waves crash against the shore is called the longshore current. Beaches are only formed if there is a gentle slope to the shore. If the rocks form a cliff, all sand will be washed back into the sea. No beach will be formed.

Tides Are the water level along the coast of a continent. The highest point is high tide and lowest point is low tide. There are two high and two low tides per day. The largest tides are called spring tides and the smallest are called neap tides. The difference between high and low tide is called the tidal range.

What Causes Tides? What Causes Currents? The gravitational force from the moon and the rotation of the Earth causes tides. Tides in Action Currents are the movement of the tides. Wind patterns determine the direction of currents. There are 3 factors that determine the direction of these winds: 1. Uneven heating of the atmosphere. 2. Rotation of the Earth 3. The position of the continents.

Current Cont’d If the current arrives from the poles, it will bring colder water, if it comes from the Equator it will bring warmer weather. Despite the fact that Europe and North America inhabit the same latitudes, Europe is traditionally warmer because it receives currents from the equator (the Gulf Stream) while we get currents from the North.

Water as a Heat Reservoir Because water has a higher heat capacity than earth, it can store heat produced in the summer and release it gradually over the winter. This explains why coastal areas such as Vancouver tend to be more temperate in temperature versus the extremes in the Prairies. However, if cold air currents dominate in an area the weather can still be cold in a coastal area (the Maritimes).