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 three main driving forces for the movement of the Earth's tectonic plates. They are mantle convection, gravity, and the Earth's rotation. Mantle convection is the most widely studied method of tectonic plate movement and it is very similar to the theory developed by Holmes in 1929.