The oceans teem with microorganisms such as bacteria, viruses, and protists. Many of these microbes fundamentally influence the ocean's ability to sustain life on Earth.
The mid-ocean ridge is an interconnected system of undersea volcanoes that meander over the Earth like the raised seams on a baseball. It is a continuous 40,000-mile (60,000-kilometer) seam that encircles Earth and bisects its oceans.
Rivers and streams transport water and sediment downslope to lakes and oceans. Along the way, sediment may be deposited, only to be eroded later during floods, and transported farther along the system.
Oceans cover 70 percent of Earth's surface, host a vast variety of geological processes responsible for the formation and concentration of mineral resources, and are the ultimate repository of many materials eroded or dissolved from the land surface. Hence, oceans contain vast quantities of materials that presently serve as major resources for humans.
Mineral waters are those that contain some dissolved minerals in sufficient concentration to change the taste or perceived health effects of the water. Mineral water originates as groundwater and flows along the local groundwater gradient, dissolving available geologic material until it reaches the surface as a spring, or until the water is pumped to the surface from a well.
As with so many other scientific fields, African Americans, Hispanics, Native Americans, and Pacific Islanders are poorly represented in the ranks of practicing water science professionals. Minority students interested in becoming oceanographers, marine biologists, fisheries scientists, hydrologists, ecologists, aquatic chemists, or limnologists have few role models to emulate.
The Mississippi River is North America's longest and largest river in terms of discharge, and the fifth largest discharge river worldwide, at an average of 17,330 cubic meters per second (811,530 cubic feet per second). The Mississippi flows 3,763 kilometers (2,333 miles) from Lake Itasca in northern Minnesota to its delta in southern Louisiana (see map).
The main purpose for numerically modeling flow and transport in groundwater systems is to solve a variety of problems. For example, a city may use groundwater to supply its public water system; city officials use a model to plan where wells should be located.
Hydrologic systems are complex, with processes occurring over different geographic areas characterized by highly variable parameters. In general, numerical models used for surface-water studies simulate the processes of interest as equations.
Moorings and platforms are structures that allow water scientists to position instruments, collect samples, and take long-term measurements in waterbodies. A mooring typically consists of a flexible cable that is tethered to the ocean floor by a weight or anchor and suspended from the sea surface by a buoy.
The science of oceanography was in its infancy in 1893 when Fridtjof Nansen, a 32-year-old Norwegian, purposely allowed his ship, the Fram, to be captured in an Arctic ice pack. Through this deliberate act, Nansen hoped to prove his theory that the Arctic current flowed from Siberia towards the North Pole and then southward to Greenland.
As concern for environmental problems grew during the 1960s, the need for better project planning to prevent environmental degradation became obvious. Too many projects (e.g., dams, power plants, highways) had been built without regard for their negative impacts on water quality, soil erosion, aquatic and terrestrial habitat, or negative economic and social impacts on nearby communities.
The National Oceanic and Atmospheric Administration (NOAA) was officially established under the U.S. Department of Commerce in 1970.
The U.S. Congress created the National Park Service (NPS) in 1916 as a bureau of the Department of the Interior.
The first Western civilization known to have developed the art of navigation at sea were the Phoenicians, about 4,000 years ago (c. 2000 B.C.E.).
Ocean basins can be described as saucer-like depressions of the seabed. They vary in size from relatively minor features of the continental margin to vast structural divisions of the deep ocean.
Biogeochemistry is the study of the interactions of the biology, chemistry, and geology of the Earth. In the case of a large body of water such as the ocean, biogeochemistry can be thought of as a huge experiment or set of reactions.
Why is the sea salty? Sea water contains about 35 grams per kilogram of dissolved salt.
Mariners have known for many centuries that the ocean contains currents that flow along generally consistent paths. The Spanish galleons transporting gold and silver from Mexico to Spain made use of the Gulf Stream to help them return home, while Benjamin Franklin used ships' log books to draw a map of this current in 1772 (see illustration on page 139 based on his original map).
The ocean has long been thought to have both a limitless bounty and ability to absorb human impacts. Its sheer volume supported the observation that "dilution is the solution" to point-source pollution, as tides and currents removed almost anything that entered the sea.
Mixing in the ocean occurs on several scales, the smallest scale being molecular. If a layer of warm, salty water lies above a layer of colder, fresher water, the heat and salt will tend to diffuse (spread out) downwards to make a single layer with intermediate temperature and salinity values.