Saltwater Systems oceans & seas cover 75% of the Earth’s surface and contain 97% of the world’s water ocean water is saline, with about 3% salt salinity is the amount of dissolved salt in liquid seas are smaller than oceans and tend to be surrounded by land

The world’s oceans can be divided into 5 regions:

Ocean Basins ocean basins are huge! they have mountains, valleys and vast plains they are formed mainly from movement of tectonic plates as they move apart ocean basins expand as they move together ocean basins shrink the average depth of the oceans is 4,000 m the deepest place is Marianas Trench at about 11,000 m Ocean Ridges from magma coming to surface in middle. Ocean Trench where one plate descends below another.

where plates pull apart magma can come to the surface and create mountains or ridges (e.g. Hawaiian Islands) where one plate slides under another a trench is often formed (e.g. Marianas Trench)

The ocean basin does not begin at the shoreline… it begins at the lower edge of the continental slope. the continental shelf and slope can be more than 300 km wide… that’s like from here to Edmonton

Ocean Temperature and Depth The Sunlight Zone The Twilight Zone The Midnight Zone ocean water also mixes from top to bottom colder water is less dense because it can hold less salt therefore it tends to rise up and mix with warmer water carried by surface currents The Abyss

Ocean Waves Energy Direction Ocean waves are just large ripples set in motion by steady winds. Height depends on how fast, long and far with wind blows over the water. Normal winds give waves 2 – 5 m high… hurricane winds give waves 30 m high. Smooth waves are called swells.

The wave collapses onshore in a tumble of water called a breaker. When Waves Hit Shore Energy Direction wave changes shape as it approaches shore - lower part of water is slowed down by friction on ocean bottom - upper part of water keeps going faster… and so tumbles over the top the tumble of water as the wave collapses onshore is called a breaker The wave collapses onshore in a tumble of water called a breaker.

Changing Shorelines waves approach shorelines at an angle and create a current along the shoreline waves erode and deposit sediments along the shore … creating interesting landscapes

Tides tides are regular cycles where ocean water levels rise and fall they are caused by the moon’s (& sun’s) gravitational pull on the water the moon rotates around the Earth and so its distance from oceans changes in 24 hours when the moon is closest to the ocean it will have high tide when the moon is farthest from the ocean it will have low tide

spring tides are the biggest variation between high & low tide very high when the moon & sun line up on the same side of the Earth and pulling together very low when the moon & sun are on opposite sides of the Earth and pulling in opposite directions neap tides are the smallest variation between high & low tide moon’s gravitational pull is at right angles to the gravitational pull of the sun

Ocean Currents 5 major gyres North Atlantic North Pacific OCEAN CURRENTS are continuous movement of ocean water 3 factors influence the direction of winds and surface currents: uneven heating of atmosphere (more at equator) – air moves from warm to cooler rotation of Earth – spins things into circular motion (turns clockwise in N, and counterclockwise in S) position of continents – deflects things along shoreline winds blowing east along the equator are called TRADE WINDS winds blowing west in the polar regions are called WESTERLY WINDS the movement of ocean currents are critical for movement of heat around the earth and gives areas on the coast a warmer, milder climate (e.g. Vancouver and Victoria) South Pacific Indian Ocean South Atlantic

The Gulf Stream a current of warm water starts in the Caribbean Sea flows north along the east coast of North America then flows across the Atlantic Ocean to England warm ocean current affect climate by transferring their heat to the atmosphere because water has a high heat capacity (takes a long time to heat up or cool down) it acts as a heat reservoir in winter and so keeps nearby land warmer than if there were no water