Interrelationships in Earth/Space Systems
5.6 The student will investigate and understand characteristics of the ocean environment. Key concepts include
a) geological characteristics (continental shelf, slope, rise);
b) physical characteristics (depth, salinity, major currents); and
c) biological characteristics (ecosystems).
· The four oceans cover about 71% of the Earth’s surface, approx. 140 million square miles. (US is only about 6 million square miles). This is 99% of the plants living space
· Life began in the seas 3.1 - 3.4 billion years ago. Land dwellers appeared 400 million years ago..
· 90% of all volcanic activity occurs in the oceans.
· Geological characteristics describe the ocean’s history &formation; land itself.
· The continental shelf is an example. It is the submerged part of the continent.
· It is usually sloping with an average depth of 400 feet and an average width of 80 km.
· Water depth at its edges is about 400 feet deep.
· The continental slope is the boundary between the continental shelf and the ocean floor.
· It is steeply sloping from 5-25 degrees and it is about 20 km wide.
· The continental rise is at the base of the continental slope when the slope angle decreases, it is made from sediments that have fallen from the continental shelf via slope.
· Physical characteristics are those characteristics that you can see or measure.
· Physical characteristics of the ocean environment are its depth, salinity, and major currents.
· The avg. depth of the ocean is 12,200 feet (over 2,000 adults standing on each others shoulders)
· The deepest point in the ocean is 36,198 feet (in the Mariana Trench in the western Pacific).
· Salinity means the amount of salt found in the ocean water.
· The salt that is in the ocean is made up of a number of different chemicals that are dissolved in the water, and are called "ions". Two of these are sodium & chloride which make up table salt.
· As the rivers move to the ocean, they dissolve the rocks that they pass over. The dissolved ions in the water make their way to the ocean. When water evaporates from the ocean and falls on land as rain, the ions are left behind in the ocean.
· The highest salinity values are found in surface waters at 20-30 degrees north and south of the equator, where evaporation is high and precipitation is low.
· Currents are large moving rivers of water in the ocean in a particular direction; oceans are always in motion due to the spinning of the earth. Currents occurring on and below the ocean surface are caused by winds and deep currents are caused by the uneven heating of ocean water by the sun. Saltier water is heavy and sinks. Less salty water moves over it. When salty water meets less salty water, a current is formed.
· Major currents include the Gulf Stream and the North Atlantic Drift.
· Biological characteristics of the ocean deal with its ecosystems, systems formed by the interaction of a community of organisms with their environment.
· The three main ecosystems are the intertidal zone, neritic zone, oceanic zone, and abyssal plain.
· The intertidal zone consists of sandy beaches, rocks, estuaries, mangrove swamps, & coral reefs
· The neritic zone is relatively shallow that extends to the edge of the continental shelf.
· The oceanic zone is over the ocean basins. Productivity is pretty much limited to the depths that light can reach.
· The flat part of the ocean floor beyond the continental slope is the Abyssal Plain, a flat, featureless region found in water 2-4 miles deep in many places and it receives hardly any light.
· The blue whale is the largest known animal ever to have lived on sea or land, they can reach over 110 feet and weigh almost 200 tons (50 elephants).
· Giant kelp is the fastest growing plant in the ocean. It grows up to 2 feet per day. More than 100 feet in a year and as much as 200 feet in its life time.