OCEANOGRAPHY EarthThe Water Planet The Water Planet of

OCEANOGRAPHY Earth-The Water Planet

The Water Planet § ¾ of earth’s surface covered by a large body of salt water called the global ocean (or hydrosphere) § This hydrosphere contains 97% of all water § 3 major oceans – Atlantic – Pacific – Indian

The Water Planet § Oceans are divided by chemical and physical characteristics § These differences blend near boundaries § Sea- a smaller area of an ocean that is partially surrounded by land

Underwater Exploration § Submersibles- underwater research vessels – Bathysphere – Bathyscaph § Sonar- Sound Navigation And Ranging – Used to map ocean floor and detect submarines § SCUBA- Self-contained Underwater Breathing Apparatus – Developed by Jaques Cousteau

The Ocean Floor • Two major divisions – Continental Margins • Made of continental crust • Thick sediments – Deep Ocean Basins • Made up of oceanic crust • Thin sediments

Continental Margin • The boundary between continental crust and oceanic crust is not the shoreline, but instead occurs many miles offshore deep beneath the ocean.

Continental Margin • Continental Shelf – Gentle slope – Relatively shallow (about 60 m) – Stretch from a few km to 1200 km from shore • Continental Slope – Steeper slope – May reach several thousand meters deep – Thick sediment deposited by rivers

Continental Margin

Deep Ocean Basin • Has all the same physical features as seen on land, such as plains, volcanic mountains, mountain ranges, deep trenches, etc… • However, in the deep ocean basin these features dwarf the similar features on land

Deep Ocean Basins • Trenches – Deepest features on Earth – Located near subduction zones – Mariana Trench • Over 11, 000 m (11 km or 7 miles) deep • Very little is known about the deepest portions

Deep Ocean Basins • Abyssal Plains – Flattest regions on Earth – Depth may change less than 3 m over 1300 km • Seamounts – Submerged volcanic mountains – Form islands when they rise above surface • Guyots – Former volcanic islands that have sunk back under water – Have flat tops, Why?

Deep Ocean Basins • Mid-Ocean Ridge – Formed along a divergent boundary – Longest mountain chains in the world – Magma escapes through rift to form new oceanic crust

Properties of Ocean Water • Chemical Properties – Chemical composition – Dissolved gases – Salinity • Physical Properties – Temperature – Density – Color

Properties of Ocean Water • Chemical Properties – About 96. 5% pure water – Rest is made up of 75 other elements, with Chlorine, Sodium, Sulfate, and Magnesium being the most abundant

Properties of Ocean Water • Chemical Properties continued – Dissolved Gases: nitrogen (N 2), Oxygen (O 2), and carbon dioxide (CO 2) – Temperature affects gas solubility, but not in the way that you might think! • Warm water has less dissolved gases than cold water

Properties of Ocean Water • Chemical Properties continued – Salinity: the ratio of dissolved solids per unit of water – Evaporation and freezing increase the salinity of ocean water – Heavy rain and freshwater runoff will decrease salinity – Salinity tends to be higher near the surface

Properties of Ocean Water • Physical Properties – Water absorbs longer light wavelengths like infrared as opposed to shorter wavelengths like blue and UV rays. – Temperature drops steadily until thermocline, where a rapid temperature drop occurs.

Properties of Ocean Water • Physical Properties continued – Density = mass/volume – Pure water has a density of 1. 00 g/cm 3, ocean water has a density of 1. 028 g/cm 3 – Salinity and Temperature affect density – The colder the water, the more dense it is

Properties of Ocean Water • Physical Properties cont. – Fluids, such as water, exert an upward force on objects that are partially or completely submerged in them. This force is known as buoyant force. – The determination of whether an object sinks or floats is dependent on the object’s density and the fluid density.

Ocean Motion • Ocean water is constantly in motion – Waves – Currents – Tides

Ocean Motion • Waves – A periodic up-and-down movement of the water normally caused by the wind – Tsunami- a seismic sea wave caused by earthquakes on the ocean floor, volcanic eruptions, and/or landslides

Ocean Motion • Ocean Currents – A giant stream or river flowing through an ocean • Surface currents • Deep currents

Ocean Motion • Surface currents are controlled by three factors – Wind belts – Coriolis effect caused by earth’s rotation – Location of the continents

Ocean Motion • Deep currents – Recall that both cold temperatures and high salinity increases the density of water. – In the polar regions, this dense water slowly sinks to the ocean floor causing a slowmoving deep current – The water moves back up to the surface through a process called upwelling

Ocean Motion • Tides – A daily change in the level of the ocean surface due to the gravitational attraction between the Earth and the Moon. – High tides occur on the sides of the Earth nearest the moon and furthest from the moon. Low tides occur half way between the two regions of high tides.

Ocean Resources • Means of Transportation • Food • Fresh Water • Minerals • Oil

Ocean Resources • Food- also called aquaculture – High-protein food using less space and cost than raising livestock on land – Used to raise catfish, salmon, oysters, and shrimp – Kelp: a form of seaweed that is used in many products that we eat today

Ocean Resources • Fresh Water – May become the most valuable ocean resource in the future – Distillation: requires heat – Freezing: requires cold temps – Reverse osmosis: Uses very fine membrane filtration – All three are very expensive BUT are currently in use in arid regions of the world

Ocean Resources • Minerals – Abyssal plains covered with nodules, large lumps of rock and minerals – The nodules contain manganese, iron, copper, nickel, and phosphates – Salt has been retrieved for centuries – Ocean is main source of magnesium and bromine today – Gold?

Ocean Resources • Petroleum – Most valuable mineral resource today – Large deposits of oil and natural gas found beneath the ocean along the continental margins – Almost ¼ of the world’s oil comes from offshore drilling

Ocean Resources • Problems – Ownership – Destruction of ecosystems – Pollution • Garbage • Sewage • Toxic waste • Runoff from land