Glossary - Environmental Science - page 321

compressed natural gas (CNG) Natural gas that is compressed to less than 1 percent of the volume it occu-
pies at standard atmospheric pressure; used primarily in cars, trucks, and buses as an alternate, cleaner-burning
fuel than gasoline or diesel.
condensation The change in the phase of water from gas to liquid, usually in the form of droplets.
conifers Cone-bearing trees (such as firs, pines, and spruces) that have needle-shaped or scaled leaves; also
known as coniferous trees.
consumer Any organism that cannot produce its own food and gets its energy and nutrients by feeding on oth-
er organisms.
continental drift The shifting of the continents due to the movement of the tectonic plates upon the astheno-
sphere.
contour farming Plowing rows into the side of a hill, perpendicular to the slope, following the shape of the
land in order to create flat terraces; used to reduce erosion and disperse water evenly throughout crops.
controlled burns See prescribed burns .
convection currents Result from fluids or gases being heated, becoming less dense as they expand, rising,
cooling, becoming denser, and sinking. Examples include the rising and sinking currents of magma below the
Earth's crust, water in the ocean, and air.
conventional agriculture Large-scale farming and livestock production in which crops are grown for many
people with the use of a variety of inputs, such as fertilizer, pesticides, irrigation, seeds, fossil fuels, monocul-
ture, and human power; also called industrial agriculture.
conventional tillage A form of farming in which soil is ploughed and turned, which ultimately can lead to soil
erosion and soil compaction in the deeper layers.
convergent plate boundary A zone where tectonic plates move toward each other, sometimes making contact.
core The dense center of the Earth. It is subdivided into the solid inner and liquid outer cores.
Coriolis effect The apparent deflection of a moving object (planetary winds, ocean currents, projectiles) due to
rotation of the Earth. These objects are deflected to the right in the Northern Hemisphere and to the left in the
Southern Hemisphere.
Corporate Average Fuel Economy (CAFE) Regulations enacted in 1975 that establish fuel economy standar-
ds across auto manufacturers' fleet of cars and trucks.
cost-benefit analysis (CBA) Used to assess the costs and benefits of a decision, helping to determine whether
a particular action should be taken.
criteria pollutants Six common air pollutants monitored by the Environmental Protection Agency and used as
a way to gauge air quality.
crop rotation The alternation of the types of crops grown on a piece of land from year to year or season to sea-
son.
crude oil A liquid combustible fossil fuel that is refined into several fuels used in transportation (gasoline,
diesel, aviation), heating oils, asphalt, and other chemicals. Many crude oil by-products are used in manufac-
turing plastics, pharmaceuticals, fertilizers, and other materials.