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.
Currents within the interior cause the plates to move, which causes many different geological events, including earthquakes and the forming of mountains and volcanoes. Understanding how plates move and interact is the main purpose of plate tectonics.