tectonic

Of or relating to the large-scale structure and movement of the earth's crust — the slow, immense forces that build mountains, open oceans, and break continents apart. Tectonic plates are the dozen or so rigid segments of the earth's outer shell, floating on the semi-fluid mantle beneath and colliding, diverging, and grinding past each other at rates measurable in inches per year. The word has come to mean any large-scale, fundamental shift — a "tectonic change" — but the geological sense is literal: the earth is being built, continuously, by forces too slow to feel and too large to see.