Circle of latitude

Tissot indicatrix world map Mercator proj

Usgs map mercator

World map with major latitude circles

Earth-lighting-summer-solstice EN

axial tilt vs tropical and polar circles

Circle of latitude refers to any parallel that is geographically significant in dividing the Earth into the Northern Hemisphere and the Southern Hemisphere. These circles are imaginary lines that run east and west around the Earth and are perpendicular to the Earth's axis and meridians of longitude. The most significant circle of latitude is the Equator, which divides the Earth into equal northern and southern halves. Other notable circles of latitude include the Tropic of Cancer, the Tropic of Capricorn, the Arctic Circle, and the Antarctic Circle. These lines are not only crucial for navigation and geography but also play a significant role in determining the climate and ecology of different regions on Earth.

Definition and Significance

A circle of latitude is defined as a circular path on the Earth's surface parallel to the Equator. It is an angle measured from the center of the Earth, ranging from 0° at the Equator to 90° at the poles. Circles of latitude are used to specify the north-south position of a point on the Earth's surface. They are significant in various fields such as astronomy, geography, and meteorology, as they affect climate patterns, day length, and the seasons.

Major Circles of Latitude

Equator (0°)

The Equator is the most well-known circle of latitude and is the only one that is a great circle. It divides the Earth into the Northern and Southern Hemispheres. Regions near the Equator experience little seasonal variation in climate and have a tropical climate year-round.

Tropic of Cancer (23.5° N)

The Tropic of Cancer marks the northernmost point at which the sun can appear directly overhead at noon. This occurs during the June solstice. Regions between the Equator and the Tropic of Cancer generally have a tropical or subtropical climate with minimal seasonal temperature variation.

Tropic of Capricorn (23.5° S)

The Tropic of Capricorn is the southern counterpart to the Tropic of Cancer and marks the southernmost latitude at which the sun can be directly overhead at noon. This happens during the December solstice. Like the Tropic of Cancer, regions between the Equator and the Tropic of Capricorn experience a warm climate year-round.

Arctic Circle (66.5° N)

The Arctic Circle marks the latitude above which, for at least one day a year, there is no sunset (the Midnight Sun) or no sunrise (polar night). This phenomenon increases in duration as one moves further north from the Arctic Circle towards the North Pole.

Antarctic Circle (66.5° S)

The Antarctic Circle is the southern equivalent of the Arctic Circle and marks the latitude below which, for at least one day a year, the sun does not rise or set. The region within the Antarctic Circle is characterized by extreme cold and long periods of darkness or continuous daylight.

Impact on Climate and Ecology

The Earth's tilt and its orbit around the sun cause the solar energy to be distributed unevenly across different latitudes, which significantly influences the climate and ecology of regions. Areas near the Equator receive more direct sunlight year-round, leading to warmer temperatures and a tropical climate. As one moves towards the poles, the angle of the sun's rays decreases, leading to cooler temperatures and, eventually, polar climates. The variation in sunlight and temperature affects the types of vegetation and animal life that can thrive in these regions.

Navigation and Mapping

Circles of latitude, along with meridians of longitude, are essential for navigation and mapping. They provide a coordinate system that can pinpoint any location on Earth. This system is crucial for various applications, including aviation, shipping, and global positioning systems (GPS).