the lowest layer of Earth’s atmosphere, where weather occurs.

the outer layer of the atmosphere, extending outward into space.

the lower part of the thermosphere, where electrically charged particles called ions are found.

the middle layer of Earth’s atmosphere; that layer in which most meteoroids burn up.

the outermost layer of Earth’s atmosphere also the hottest layer.

a colorful, glowing display in the sky caused when particles from the sun strike oxygen and nitrogen atoms in the ionosphere; also called the Northern Lights.

rain that is more acidic than normal, caused by the release of molecules of sulfur dioxide and nitrogen dioxide into the air.

the invisible, gaseous form of water.

the amount of mass in a given space; mass per unit of volume.

the condition of Earth’s atmosphere at a particular time and place.

the mixture of gases that surrounds Earth. The outermost of the four spheres into which scientists divide Earth.

an instrument that measures changes in air pressure, consisting of a glass tube part filled with mercury, with its open end resting in a dish of mercury.

when a layer of warm air prevents the rising air from escaping.

an instrument that measures changes in air pressure without using a liquid.

a force that is the result of the weight of a column of air pushing down on an area.

an instrument used to measure changes in air pressure.

elevation above sea level.

a form of oxygen that has three oxygen atoms in each molecule instead of the usual two.

a brownish haze that is a mixture of ozone and other chemicals, formed when nitrogen oxides, hydrocarbons, and other pollutants react with one another in the presence of sunlight.