Oceans Water, Motion, Exploration, and Life

Origin of Oceans Earth was not always a blue planet. About 4 billion years ago, Earth’s volcanoes began releasing water vapor. As the water vapor rose it began to cool and condense on soot particles in the upper atmosphere. As the drops got too heavy to be supported by the heat rising from Earth’s surface, they fell as rain. The rain slowly filled the low spots, basins, to create oceans.

Contents As the water filled the oceans, it dissolved a lot of minerals –Chlorine (55%) –Sodium (30.6%) –Sulfate (7.9%) –Magnesium (3.7%) –Calcium (1.2%) –Potassium (1.1) These minerals make up 3.5% of Ocean water

Contents (cont) Even today dissolved minerals are being added to the ocean. Animals and plants use these minerals –Ex Shells Solid minerals also form on the bottom of the ocean to keep the Salinity, or amount of salt in the ocean, near constant. Warm waters have higher amounts of dissolved minerals

Currents There are two types of currents Surface currents are caused by wind. The Coriolis Effect causes surface currents in the Northern Hemisphere to rotate clockwise and vice versa. The Gulf Stream is a surface current that runs north along the US east coast.

Density Currents Density Currents occur due to differences in density Density determines how heavy a certain sized amount of something is. Two things affect the density of water in the oceans –Salt –Temperature

Density Currents (cont) Warm water that is low in salt rises to the surface at the equator. Near the poles as the water freezes, it leaves behind salt which makes the cold water even denser. This cold, salty water falls to the ocean floor and heads back to the equator. This creates a conveyor belt that distributes heat around Earth

Upwelling Upwelling occurs when water from the ocean floor flows up to the surface. It brings nutrients from the floor of the ocean up to the surface. Areas where upwellings occur support large ecosystems.

Waves Waves, like surface currents are caused by friction between the ocean and wind. Waves have parts. –Crest, Trough, Wave Height, Wave Length The individual particles of water do not move very far, only the energy travels anywhere.

Breakers As waves get closer to shore, they encounter more friction with the ocean floor. This causes the wavelengths to get shorter. As the wave gets even closer to shore the friction becomes so great that the top of the wave moves faster than the bottom wave causing it to fall over.

Tides (review) Tides are caused by gravity from the moon. An area along a shoreline will experience two high tides and two low tides each day. The difference between high tide and low tide is the tidal zone.

Energy from Tides We can harvest the energy from tides to create electricity. Tidal dams allow water to flow in freely as high tide approaches. After high tide, seawater that is moving away from shore is diverted into channels containing turbines that spin to create electricity.

Shoreline Where the ocean meets the land is called the shoreline. Shorelines look very different around the world. There are two basic types of shorelines –Rocky –Sandy

Rocky Shorelines Rock shorelines are characterized by large rocks and cliffs. Fast moving waves crash into the shore and cause lots of erosion. The sediment that is eroded is carried away to be deposited either on the ocean floor or elsewhere along the shoreline.

Beaches As waves approach land at an angle they cause longshore currents which move around sediments. When longshore currents slow they deposit more than they erode leaving behind beaches. Beaches can be made of sand, shells, volcanic rock, and can be a variety of colors

Barrier Islands Barrier Islands form in the same way beaches do. Seawater loses energy and deposits sediment creating a sandbar. Eventually the sandbar will reach the surface creating an island. Barrier islands are not permanent and usually last for a few centuries.

Into the Deep As one leaves the shore and heads out into the ocean they will encounter some common features –Continental Shelf and Slope –Abyssal Plain –Seamounts and Islands –Rifts, Ridges, and Trenches

Continental Shelf and Slope The continental shelf is a fairly flat continuation of the land. Where the continental shelf ends a step drop off occurs called the continental slope. After that drop-off the ocean floor levels off creating the abyssal plain.

Seamounts and Islands Volcanoes occur on the the abyssal plain forming seamounts and islands. Because they are under the water, erosion acts slowly, so these volcanoes grow tall and steep. If they have not broken the surface they are seamounts, if they have they are islands.

Rifts and Ridges Rifts occur where cracks in the seafloor spread apart as lava flows in to fill the void. As the seafloor is pushed outward it buckles creating long mountain chains called ridges. These places are home to interesting creatures.

Trenches Trenches are the opposite of ridges. The occur where the seafloor is being squeezed together. One part of the seafloor moves below the other. The deepest trench in the world is the Marianas Trench

Life in the Ocean The oceans are teeming with life. Most life in the ocean is relies upon photosynthesis to get energy from the sun. Some life gets its energy from the heat and chemicals along mid-oceanic ridges, chemosynthesis. Both systems rely on respiration to harvest that energy

Classification Plankton- organisms, usually too small to see without a microscope, that just drift with ocean currents. Nekton- organism that are large and strong enough to swim and control their motion. Benthos- organisms that primarily live on the ocean floor (some swim, some don’t)