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.
There are mainly three causes for the movement of mechanically stronger tectonic plates (lithosphere) over the mechanically weaker asthenosphere. These are Mantle convection, ridge push and the slab pull. Mantle convection occurs because of the density difference and the heat release in the mantle.