Ocean-Floor Bathymetry

Bathymetric mapping involves the production of ocean and sea maps based upon bathymetric data (see historic map). Bathymetric maps represent the ocean depth as a function of geographical coordinates in the same way topographic maps represent the altitude of Earth's surface at different geographic points.

Ocean-Floor Sediments

Sediment on the seafloor originates from a variety of sources, including biota from the overlying ocean water, eroded material from land transported to the ocean by rivers or wind, ash from volcanoes, and chemical precipitates derived directly from sea water. A very small amount of it even originates as interstellar dust.

Oceanography, Biological

Biological oceanography is a field of study that seeks to understand what controls the distribution and abundance of different types of marine life, and how living organisms influence and interact with processes in the oceans.

Oceanography, Chemical

Oceanography is the scientific discipline that studies Earth's oceans. Chemical oceanography is concerned with the study of the dissolved elements in sea water and the ocean's numerous chemical and biochemical cycles.

Oceanography from Space

The use of space satellite data for ocea n observations allows marine scientists to view biological, chemical, and physical interactions within the oceans on regional and global scales. Satellite studies have revolutionized our ideas of how the ocean works.

Oceanography, Geological

Geological oceanography is the study of Earth beneath the oceans. A geological oceanographer studies the topography, structure, and geological processes of the ocean floor to discover how the Earth and oceans were formed and how ongoing processes may change them in the future.

Oceanography, Physical

Although oceanography is the scientific study of the ocean, the subdiscipline of physical oceanography is principally concerned with the study of the structure and movement of water in the oceans. Physical oceanographic studies utilize a number of scientific specialties, and studies can encompass a diversity of technologies—from echo-sounding determinations of seafloor structure and seismic studies of movements in oceanic crust to satellite estimations of current flow based on radar reflections and thermal imaging.

Oceans, Polar

The Arctic Ocean and the Southern Ocean (the ocean around Antarctica) have different characteristics than the rest of the world's oceans in terms of circulation, formation of bottom water, convergent and divergent water masses, productivity, ice cover, and biological diversity. In addition, polar oceans are inextricably linked to climate change, and hence continued to be studied in the context of global warming.

Oceans, Tropical

Tropical oceans encircle Earth in an equatorial band between the Tropic of Cancer (23.5° North latitude) and the Tropic of Capricorn (23.5° South latitude).* The central portions of the Pacific and Atlantic Oceans and most of the Indian Ocean lie in the tropics. The warm tropical oceans play a critical role in regulating Earth's climate and large-scale weather patterns.

Ogallala Aquifer

The Ogallala Aquifer occupies the High Plains of the United States, extending northward from western Texas to South Dakota. The Ogallala is the leading geologic formation in what is known as the High Plains Aquifer System.

Oil Spills: Impact on the Ocean

Oil wastes that enter the ocean come from many sources, some being accidental spills or leaks, and some being the results of chronic and careless habits in the use of oil and oil products. Most waste oil in the ocean consists of oily stormwater drainage from cities and farms, untreated waste disposal from factories and industrial facilities, and unregulated recreational boating.

Petroleum from the Ocean

Petroleum (literally, "rock oil") is a substance that has formed beneath the surface of the Earth over eons. The remains of ancient plants and animals have been buried and compressed beneath thousands of feet of sand, mud, and rock.


Awareness is growing regarding the importance of the oceans and the variety of life they support. Research in many branches of oceanography is discovering the vast unknown of the marine world, and has expanded interest in the understanding of the marine environment and the role each member plays in a complex community.

Planning and Management, History of Water Resources

Few governmental functions have been more important historically than managing water. Early in United States history, despite some questions over the constitutionality of the federal government getting involved in local and regional economic development, most people recognized that a partnership between government and the private sector was needed in order to plan for and manage the coastal and inland waterways of the new nation.

Planning and Management, Water Resources

Most public utilities engage in some form of planning, although the extent and scope of planning vary greatly. Utility planning can be characterized by four general approaches: traditional supply planning, least-cost utility planning, integrated resource planning, and total water management.

Plate Tectonics

Plate tectonics is the unifying theory of geology that describes and explains that all earthquakes, volcanic activity, and mountain-building processes are caused by the gradual movement of rigid slabs of rock, called plates, that make up the Earth's surface layer. Given the expanse of geologic time, even modest movements—measured in centimeters or inches per year—result in substantial changes in the distribution of lands and oceans over millions of years.

Policy-Making Process

Public policies are developed by officials within institutions of government to address public issues through the political process. When it comes to creating public policy, policymakers are faced with two distinct situations.

Pollution by Invasive Species

Plants and animals sometimes disperse naturally into new habitats, either by natural migrations or via floods, storms, and other events. Species also can be transported by humans, either deliberately or accidentally.

Pollution of Groundwater

About half the population in the United States relies to some extent on groundwater as a source of drinking water, and still more use it to supply their factories with process water or their farms with irrigation water. However, if all water uses such as irrigation and power production are included, only about 25 percent of the water used nationally is derived from groundwater.

Pollution of Groundwater: Vulnerability

The water that individuals drink is the same water that falls in the form of rain on the fields that produce crops and graze livestock, the fertilized lawns in residential neighborhoods, and the oil-stained parking lots in major cities. Potential contaminants can be found in every rural area, in every suburban community, and on every city block.

Pollution of Lakes and Streams

Pollution is defined as "to make something impure"—in this case, the fresh water in lakes, streams, and groundwater. The pollution of water restricts its use for some human need or a natural function in the ecosystem.

Pollution of Streams by Garbage and Trash

Despite environmental regulations that protect the quality of streams, lakes, and wetlands, solid waste in the form of trash, litter, and garbage often ends up in these surface waters. Because surface waters collect in low-lying areas, anything that is dropped or blown into a watershed can eventually reach a drainageway.