A medial moraine, when of sufficient thickness, protects the ice underneath it from melting; so that the moraine will often appear to be much larger than it really is: what seems to be a ridge of earthy material being in reality a long ridge of ice, thinly covered with earthy _débris_, sliding down the slanting sides as the ice slowly wastes away Large blocks of stone in the same manner protect the ice from melting underneath, and are found standing on pedestals of ice, often several feet in height. An interesting feature of these blocks is that, when the pedestal fails, the block uniformly falls towards the sun, since that is the side on which the melting has proceeded most rapidly. If the meteorological forces are so balanced that the foot of a glacier remains at the same place for any great length of time, there must be a great accumulation of earthy _débris_ at the stationary point, since the motion of the ice is constantly bearing its lines of lateral and medial moraine downwards to be deposited, year by year, at the melting line along the front. Such accumulations are called _terminal_ moraines, and the process of their formation may be seen at the foot of almost any large glacier. The pile of material thus confusedly heaped up in front of some of the larger glaciers of the world is enormous. The melting away of the lower part of a glacier gives rise also to several other characteristic phenomena. Where the foot of a glacier chances to be on comparatively level land, the terminal moraine often covers a great extent of ice, and protects it from melting for an indefinite period of time. When the ice finally melts away and removes the support from the overlying morainic _débris_, this settles down in a very irregular manner, leaving enclosed depressions to which there is no natural outlet. These depressions, from their resemblance to a familiar domestic utensil, are technically known as _kettle-holes_. The terminal moraines of ancient glaciers may often be traced by the relative abundance of these kettle-holes.