Introduction to Earth. Chp. 1 (Glossary)

parallel

A line connecting all points of equal latitude; such a line is parallel to all other parallels.

meridian

An imaginary line of longitude extending from pole to pole, crossing all parallels at right angles, and being aligned in true north-south directions.

Universal Time Coordinated (UTC) or Coordinated Universal Time

The world time standard reference; previously known as Greenwich Mean Time.

hydrosphere

Total water realm of Earth. Including the oceans, surface waters of the lands, groundwater, and water held in the atmosphere.

North Pole

Latitude of 90 degrees north

South Pole

Latitude of 90 degrees south.

longitude

Location described as an angle measured (in degrees, minuets, and seconds) east and west from the prime meridian on Earth's surface.

September equinox

One of two days of the year when the vertical rays of the Sun strike the equator; every location on Earth has equal day and night; occurs on or about September 20 each year.

time zone

Region on Earth (generally a north-south band defined by longitude) within which the agreed-upon local time is the same.

Parallelism

See polarity.

daylight-saving time

Shifting of clocks forward one hour.

analemma

Shows the latitude of the vertical rays of the noon Sun.

physical geography

Study of the physical elements of geography.

cryosphere

Subsphere of the hydrosphere that encompasses water frozen as ice or snow.

lithospere

Tectonic plates consisting of the crust and upper ridge mantle. Also used as a general term for the entire solid Earth (one of the Earth "spheres").

circle of illumination

The edge of the sunlit hemisphere that is a great circle separating Earth into a light half and a dark half.

atmosphere

The gaseous envelope surrounding earth.

plane of the ecliptic

The imaginary plane that passes through the Sun and through Earth at every position in its orbit around the Sun. The orbital plane of Earth.

International Date Line

The line marking a time difference of an entire day from one side of a line to the other. Generally, this line falls on the 180th meridian except where it deviates to avoid separating an island group.

biosphere

The living organisms of earth.

prime meridian

The meridian passing through the Royal Observatory at Greenwich (England), just east of central London, and from which longitude is measured.

March equinox

One of two days of the year when the vertical rays of the Sun strike the equator; every location on Earth has equal day and night; occurs on or about March 20 each year.

revolution [around the Sun]

The orbital movement of Earth around the Sun over a year.

inclination [of Earth's axis]

The tilt of Earth's rotational axis relative to its orbital plane.

equator

The parallel of 0 degrees latitude.

Tropic of Cancer

The parallel of 23.5 degrees N latitude, which marks the northernmost location reached by the vertical rays of the Sun in the annual cycle of Earth's revolution.

Tropic of Capricorn

The parallel of 23.5 degrees S latitude, which marks the southernmost location reached by the vertical rays of the Sun in the annual cycle of Earth's revolution.

Antarctic Circle

The parallel of 66.5 degrees south latitude.

Arctic Circle

The parallel of 66.5 north latitude.

aphelion

The point in Earth's elliptical orbit at which earth is farthest from the sun (about 152,100,00 kilometers or 94,500,000 miles).

perihelion

The point in its orbit where Earth is nearest to the Sun (about 147,100,000 kilometers or 91,400,000 miles).

rotation [of Earth]

The spinning of Earth around its imaginary north-south axis.

cultural geography

The study of the human and/or cultural elements of geography.

Greenwich Mean Time (GMT)

Time in the Greenwich time zone. Today more often called UTC or Universal Time Coordinate.

polarity

A characteristic of Earth's axis wherein it always points towards Polaris at every position in Earth's orbit around the Sun.

solar altitude

Angle of the Sun above the horizon.

great circle

Circle on a globe formed by the intersection of Earth's surface with any plane that passes through Earth's center.

June solstice

Day of the year when the vertical rays of the Sun strike the Tropic of Cancer; on or about June 21; summer solstice in the Northern Hemisphere.

December Solstice

Day of the year when the vertical rays of the Sun strike the Tropic of Capricorn; on or about December 21;winter solstice in the Northern Hemisphere.