Most glaciers move very slowly—only a few centimeters a day. Some, though, can move 50 meters (160 feet) a day. These fast-moving rivers of ice are called galloping glaciers.

Perito Moreno is perhaps the region’s most famous glacier because it periodically cuts off the major southern arm (known as Brazo Rico) of Lake Argentino. The ice dam prevents lake water from circulating from one side to the other, which in turn causes muddier and “milkier” water to concentrate in Brazo Rico.

Perito Moreno is one of the few glaciers that is not shrinking. It is in a relatively steady state with no major changes in its average size over the last 100 years.

Walking on one of Argentina’s biggest tourist attractions is truly sensational. You can book short Perito Moreno Glacier tours (known as ‘Mini Trekking’) or the larger ‘Big Ice’ which lasts for a few hours more and can even go inside ice caves depending on the time of year.

Perito Moreno is one of the only glaciers in the world that is growing instead of shrinking. Exactly why the glacier is growing while others around the world are shrinking is a bit mysterious.

Pakistan has more glaciers than almost anywhere on Earth.

Jakobshavn Isbrae

A glacier is slowest moving where it comes in contact with the ground. This is actually a pervasive physical phenomena that is also true about other flowing mediums like air moving over an airplane wing or water flowing down a river. This is referred to as a “boundary layer” in engineering.

Glaciers and their immediate environs present many dangers for humans, such as crevasses and glacier mills into which one might fall, heavily crevassed ice falls, snow and ice avalanches from the side walls and, along the flanks, dumping of great boulders, ponding and floods from melt water.

30 metres per day

Even as it retreats, the glacier still deforms and moves downslope, like a conveyor belt. In other words, a retreating glacier does not flow uphill; it simply melts faster than it flows. Alternatively, glaciers may surge, racing forward several meters per day for weeks or even months.

Ice Flow: Glaciers move by internal deformation (changing due to pressure or stress) and sliding at the base. Also, the ice in the middle of a glacier actually flows faster than the ice along the sides of a glacier as shown by the rocks in this illustration (right).

One of the glaciers on Alaska’s Denali mountain has started to “surge.” The Muldrow Glacier is moving 10-100 times faster than usual, which is about three feet per hour. About 1% of glaciers “surge,” which are short periods where glaciers advance quickly.

“When the glacier becomes thicker, the pressure in the ice increases, resulting in some increase in temperature. At the bottom of thick glaciers, the ice is so warm that it starts to melt. The secret of such pulsating glaciers is therefore increased pressure from above.

The flow instability that results in glacier surges is generally caused by an abrupt decoupling of the glacier from its bed. This decoupling is the result of a breakdown in the normal subglacier water flow system, but the exact mechanisms that cause some glaciers to surge are not fully understood.

A glacier might look like a solid block of ice, but it is actually moving very slowly. The glacier moves because pressure from the weight of the overlying ice causes it to deform and flow. Occasionally a glacier speeds up. This is called surging. A surging glacier can advance tens or even hundreds of metres a day.

temperature: in general, temperate and polythermal glaciers flow at greater velocities than polar glaciers. This is because temperate and polythermal glacial ice is warmer and is therefore able to deform more easily and, further, the presence of meltwater at their base promotes basal sliding.

Glaciers move by a combination of (1) deformation of the ice itself and (2) motion at the glacier base. This means a glacier can flow up hills beneath the ice as long as the ice surface is still sloping downward. Because of this, glaciers are able to flow out of bowl-like cirques and overdeepenings in the landscape.

Internal deformation (or creep) is the movement of an ice mass through the deformation of glacier ice itself. In the case of glacier dynamics it is most often the force that is applied to glacier ice due to the ice surface slope. Yield stress is the stress at which a material begins to deform plastically.

Rates of glacial erosion vary widely as a function of basal temperature, resistance of subglacial rock or sediment, and subglacial meltwater flow. High rates of erosion produce large volumes of glacial and proglacial sediments and contribute to the fundamental reshaping of glaciated landscapes.

about 20,000 years ago