Geography Quiz: Important Geographical Terms and Isolines

The word comes from the Greek hyetos, meaning rain, so an isohyet joins all places on a map that receive the same amount of rainfall in a given period; rainfall distribution maps of India, which show the 200 centimetre and 50 centimetre lines, are drawn with isohyets.

An isohel, from the Greek helios for the sun, joins places that receive sunshine for an equal number of hours, and such maps are used in studies of solar energy potential and of crop seasons.

The Greek bathos means depth, so isobaths are the depth contours of a bathymetric chart; the 200 metre isobath is conventionally taken as the outer edge of the continental shelf.

Isoseismal lines join points at which the shaking of an earthquake was felt with the same intensity, and because intensity falls away from the source, they are drawn as roughly concentric closed curves around the epicentre, the point of the surface vertically above the focus.

Magnetic declination is the angle between true north and magnetic north, and along the agonic line that angle is zero, so a compass needle there points to true north.

The Isthmus of Panama joins North and South America and separates the Caribbean Sea from the Pacific, and the Isthmus of Suez joins Africa to Asia; both have been cut by canals precisely because they are narrow.

In Alfred Weber's least-cost theory of industrial location, isodapanes are drawn through all points at which the total transport cost, for assembling the raw materials and for distributing the finished product, is the same; the innermost isodapane marks the area of least total cost, where the plant should be sited.

A contour, whose technical name is isohypse, joins all points standing at the same height above sea level and is the chief means of showing relief on a topographical sheet; contours drawn close together mean a steep slope, contours far apart a gentle slope, and contours that merge indicate a…

The earth's orbit is an ellipse, so its distance from the sun changes through the year; at perihelion, about 3 January, the earth is nearest the sun, which is why the northern winter half of the year is slightly shorter than the summer half.

Salinity is the quantity of dissolved salts in a kilogram of sea water, expressed in parts per thousand, and isohalines map its distribution; the open ocean averages about 35 parts per thousand, while enclosed seas with high evaporation such as the Red Sea are far saltier and seas fed by…