Isograds

Part of speech: noun

Definitions

1. A series of lines on a map connecting points of equal geological gradient or metamorphic intensity
2. Representing locations where specific geological conditions occur uniformly across a landscape
3. Characterizing contours that indicate levels of change within rock formations and their metamorphic processes

Etymology: "Isograd" is a technical coinage, not an ancient word. It is formed from Greek "isos," meaning "equal," and "-grad," from Latin "gradus," meaning "step" or "degree," as in "gradient." Together they describe a line of equal degree, a contour joining points that share the same value of some measurable quantity. The plural "isograds" is simply the plural of "isograd," used when a map shows several such lines at once. Geologists and mapmakers apply the term to boundaries that mark where a particular condition, such as a mineral or metamorphic change, first appears across a region.