Water

The Earth’s ice

Clear distinction must be made between the ice covering lands above sea level and sea ice floating in the Polar seas. In order to be considered a glacier, the ice must move under the thrust of its own weight : therefore sea ice or icebergs, even though they move at times, cannot be considered glaciers, as their movement is passive, generated by sea currents, wave motion or winds. Even though they are formed by the same material, the Earth’s glaciers are very different one from the other, in extension, ice-thickness, geographical position and climate regime, topographical situation and shape. All these factors determine, besides quite a different appearance, also a very different behaviour and a different response to climatic variations. Researchers who study glaciers use many different classifications, some are rather complex, also depending on the type of study that one intends carrying out. A first, important distinction can be made between frozen ice , that includes sea ice and permafrost, and glacier ice, that includes the ice-sheets, ice shelves and mountain glaciers.