Glossary - Environmental Science - page 330

nonrenewable resource A resource with a finite supply that has the potential to be renewed only over hun-
dreds of millions to billions of years. Nonrenewable resources include fossil fuels and metals.
normal fault A fault caused by tectonic plates or rock strata pulling apart.
no-till farming A farming method in which soil is minimally disturbed while it is being prepared for crops.
nuclear energy The energy stored in the nuclei of atoms. It is released by the splitting (fission) or the joining
(fusion) of atoms.
nuclear fission The process of an atom splitting into two smaller elements, releasing neutrons and heat energy.
In nuclear power generation, fission is caused by bombarding unstable elements with neutrons.
nuclear fusion The process in which the atomic nuclei of two elements are forced together under high pres-
sure, releasing large amounts of energy under conditions present in stars, such as the sun.
oil A liquid fossil fuel derived from crude oil .
oil sands See tar sands .
oil shale Sedimentary rock that is rich in kerogen, an organic compound from which liquid hydrocarbons can
be extracted when heated.
old growth A forest prior to its trees ever being harvested.
omnivore An animal that eats both plants and other animals as a source of energy and nutrients.
open pit mining Mining that involves digging up the land in order to reach the desired resource.
ore Rock containing desired mineral elements or molecular compounds.
organic farming Farming or livestock raising that uses no chemicals, including pesticides, hormones, fertil-
izers, or antibiotics.
outer core The liquid part of the Earth's core; comprised mainly of molten iron and nickel.
overnutrition A condition resulting from people receiving too many calories on a daily basis, leading to
obesity and many other health issues.
ozone (O 3 ) A colorless gas found in both the stratosphere and troposphere. "Good" ozone is located naturally
in the stratosphere and protects the Earth from the sun's harmful ultraviolet radiation. "Bad" ozone is located
close to the ground in the troposphere, is the main component of smog, and is considered a greenhouse gas.
ozone depletion The loss of ozone in the stratosphere (for example, as a result of CFCs).
ozone hole An area of depletion in the ozone layer that forms over Antarctica and the Arctic and moves toward
the equator.
ozone layer The concentration of ozone in the stratosphere that helps protect the Earth from harmful UV radi-
ation.
parasite Any organism that uses another organism for food and nutrients at a cost to the host.
parasitism A species interaction in which one organism uses another organism for food and nutrients, harming
the host.