a branch of the Indo-European family of languages, including especially Irish, Scottish Gaelic, Welsh, and Breton, which survive now in Ireland, the Scottish Highlands, Wales, and Brittany. adjective. 2. of the Celts or their languages.
Movement of tectonic plates-higher. Volcanoes, mountains and earthquakes occur at the edges of tectonic plates-their creation depends on the direction the plates are moving.
Much of what occurs near the surface of the Earth is due to interactions of the lithosphere with the underlying asthenosphere. Most of these interactions are caused by plate tectonics. Plate Tectonics is a theory developed in the late 1960s, to explain how the outer layers of the Earth move and deform. The theory has caused a revolution in the way we think about the Earth.