Explain the process of Basal Sliding

Whilst cold based glaciers generally move by internal deformation, warm based valley glaciers, found in places such at The Alps, predominately move by basal sliding. Basal sliding occurs when the temperature at the base of the glacier is above pressure melting point (the temperature where ice is on the verge of melting) and so melting can occur. Melting facilitates glacier movement as friction is reduced and so the ice can slide over the valley floor. Therefore rates of movement greatly depend on the availability of meltwater. Meltwater is increased by a rough valley floor as this increases friction, the heat from which is used to produce more lubricating meltwater. In contrast, cold based ice sheets such as Antartica cannot move by basal sliding as temperatures at the base of the ice sheet are well below pressure melting point and so melting is inhibited.