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"Ocean Waters and the Ocean Floor" The Vast World Ocean • 71% of Earth is covered with water (about 140/197 million square miles) The Northern Hemisphere is 61% water 39% land, while the Southern Hemisphere is 81% water, 19% land. The total volume of all the land on the Earth is only 1/18 of the total volume of water. • The average depth of any of the oceans is 12,500 feet. • The Pacific Ocean is the largest, and contains that Marianas Trench - the deepest place anywhere on Earth. Composition of Sea Water • For every thousand parts of sea water, 35 parts are salt. This can be expressed as 35 ppt (parts per thousand). This is also called salinity, or the ratio of salts to pure water. • Salt is mainly sodium chloride, or common table salt. • 8 different elements make up the 5 types of salt. • In areas of heavy precipitation, the salt concentration is less. • In areas of high evaporation, there is more parts of salt per thousand parts of sea water. • Extremes in salinity: The Red Sea has about 42 ppt, while the Baltic Sea has only 10 ppt. Where does salt come from? • Chemical weathering on land and runoff into the ocean brings about 2.5 billion tons of salt per year. -Volcanic eruptions, and the process of outgasing emits water and dissolved gases into the ocean and atmosphere. -The amount of salt in the oceans hasn't changed, as various ocean-dwelling plants and animals use salt in different ways. Resources from Sea Water • -Salt, magnesium, and bromine are valuable resources. Salt is extracted by a process called Solar Salt Production -In the 1960's, a lot of these products were taken out of the ocean. Now, the USA uses the Great Salt Lake as a resource rather than the ocean. -Freshwater - desalination can be a costly process, and it is a small production. -Even gold can be taken of the ocean, but the concentration is extremely low. Click on the picture to read about the Meteor expedition lead by Germany after WWI. Meteor Expedition The Ocean' Layered Structure • -Temperature and salinity vary with depth. -The surface mixed zone is the warmest and makes up 2% of all the oceans. -The transition zone is the next warmest and makes up 18% of the oceans. -The deep zone is the coldest and makes up 80% of all the oceans. -A thermocline is a change in temperature -A halocline is a change in salinity. Earth Beneath the Sea • -The H.M.S. Challenger was one of the first ships to do extensive oceanic studies. -The echo sounder was an innovation that allowed for a lot of research to be able to be conducted about the ocean's floor. -Here is a problem: Sound travels 5000 ft. per second through water. It takes one second for the echo to go from the ship and then be bounced off the bottom and return to the ship. The total distance is 5000 feet, so you know from the ship to the ocean floor it is half of that, or 2500 feet. The formula 1/2(5000)(time traveled) can be used anytime. H.M.S. Challenger Continental Margins • Click here to learn more about continental margins, continental slope & rise. Submarine Canyons and Turbidity Currents • -Submarine canyons, steep walled underwater vallies, are created by turbidity currents. Click on the links to learn more about them. The Ocean Basin Floor • -30% of the Earth's surface are made up by these landforms: -Deep ocean trenches, where 2 converging plates meet, are the deepest regions of Earth. The Marianas trench can reach up to 36,000 ft. deep. -Abyssal plains are very flat regions made of the sediment carried by turbidity currents. -Seamounts are isolated volcanic peaks made by hotspots, like Hawaii. Others are near ocean ridges. Others emerge as land, like St. Helena. Below From left: A deep ocean trench, the topography of an abyssal plain, and the location of some seamounts across the globe. Trench Abyssal Plain Seamounts Mid Ocean Ridges • This is where sea floor spreading occurs, and new crust is formed. -These regions make up to 20% of the Earth's surface -They run a course of 40,000 miles around the Earth that looks like a baseball seam. -Click here to learn about the Mid-Atlantic Ridge (below, the MAR is on land in Iceland) Coral Reefs and Atolls • Coral reefs are made of skeletal remains from coral polyps and algaes. • They live in warm waters, above 75 degrees F anually. • The H.M.S. Beagle expedition did research atolls and their locations. • Atolls are islands made out coral. of Seafloor Sediments • -Seafloor sediments can be up to 6 miles deep in some places -It is mainly mud -There are 3 broad categories of sediment: -Terrigenous, which are minerals that were weathered from continental rocks and then brought to the ocean. -Biogenous, which is made of shells and skeletons of marine life. -Hydrogenous, which are minerals that crystallize from seawater. Manganese nodules are a type of this kind of sediment. They are one of the slowest chemical reactions known. Seafloor Sediments and Climate Change • -Scientists use sediment from the ocean floor to examine past climates, using shells from old animals that died and became incorporated into the sediment. -Deep ocean drillings also help to determine climates from periods of time lke te ice age. Click to learn about the JOIDES Resolution ship from the Ocean Drilling Program Joides Resolution • Plate Tectonics