Geography is the science that studies the relationships among natural systems, geographic areas, human culture, and the interdependence of all of these, over space. The unifying method of geography is spatial analysis, the view of phenomena across space. Geographic teaching and research has traditionally been divided into five themes: location, place, movement, region, and human-Earth relationships.
Geography splits broadly into physical geography and human geography. Physical geography is the spatial study of all the elements, processes, and systems that make up the natural environment. Physical geography encompasses the field of Earth systems science, the area of study that seeks to understand Earth as an interacting set of physical, chemical, and biological systems.
An open system is not self-contained: energy and matter flow in and out. A closed system is self-contained: it is shut off from the surrounding environment. Earth is an open system for energy flows and a closed system for material flows. As a system operates, it generates outputs that influence its own operations, forming pathways called feedback loops. If the feedback information discourages change in the system (when performing an action leads to fewer performances of that action), it is negative feedback. If the feedback information encourages change in the system, it is positive feedback. Negative feedback leads to stability. Positive feedback leads to instability. A steady-state equilibrium is reached when the rates of inputs and outputs in the system are equal and the amounts of energy and matter in storage within the system fluctuate around a stable average.
There are four immense open systems that interact over Earth’s surface. The atmosphere is a thin gaseous veil surrounding the Earth. The hydrosphere encompasses all of Earth’s waters. The lithosphere includes the Earth’s crust and a portion of the upper mantle. The biosphere includes all the living organisms on Earth, linked with their physical environment.
Geodesy is the science that determines Earth’s shape and size. Earth is an oblate spheroid, or, more correctly, an oblate ellipsoid. The more rapid rotational speed at the equator produces an equatorial bulge.
Latitude is the angular distance north or south of the equator, measured from the center of Earth. A parallel is a line connecting all points along the same latitude. The equator divides the distance between the North Pole and South Pole exactly in half and is designated 0° latitude. Longitude is the angular distance east or west of a point on Earth’s surface, measured from the center of Earth. A meridian is a line connecting all points along the same longitude. The prime meridian is the arbitrary line of longitude that is designated 0° longitude. The International Date Line is (approximately) the 180° meridian (opposite the Greenwich prime meridian) and marks the place where each day officially begins. A great circle is any circle of Earth’s circumference whose center coincides with the center of Earth.
Cartography is the science and art of mapmaking. A map is a generalized view of an area as seen from above and greatly reduced in size. A map projection is the reduction of a spherical Earth to a flat surface. The main map projection classes include the cylindrical, planar, and conic. The Mercator projection is a true shape (conformal) cylindrical projection. A rhumb line is any straight line on the Mercator map. The Eckert IV projection is an equal area pseudocylindrical projection. A gnomonic projection is a type of planar projection which shows great circles as straight lines. A topographic map shows position and elevation on Earth’s land surface using contour lines connecting all points at the same elevation.
—July 2020
Lance Jones 