How fast does a glacier move?

Question

And why is it considered one of the most powerful forces on the planet?

Answer 1

You've got two questions there, which you've already got some good answers for above.

A glacier forms anywhere that more snow accumulates than melts, over a period of many years. Snow builds up in the zone of accumulation, turns to ice under great pressure, and begins to flow downhill to a lower elevation where it either melts or calves into the sea at the zone of ablation.

Therefore the speed of a glacier depends on many factors which we don't completely understand, but mainly the steepness of the surface that the glacier is moving on. Same goes for a bike or a skateboard, the steeper the hill, the faster you go. That's gravity.

Other factors are the thickness of the ice, the volume (mass) of ice pushing behind it, temperature, how smooth the bedrock below the glacier is, how straight the route is, and how much water is acting as a lubricant below the glacier (but that is disputed by some glaciologists).

There is also a phenomenen called a jokullaup or glacier surge, where a glacier that normally moves slowly can suddenly advance hundreds of meters in one day (jokullaup is an Icelandic word for running glacier). Some examples of surging glaciers are the Bering Glacier in Alaska, the Tulsequah Glacier in British Columbia, and the Brúarjökull Glacier in Iceland. What causes a jokullaup event is not known.

Most glaciers move tens or a few hundred meters per year, but that shouldn't be confused with advancing and receding. An advancing glacier is one that moves ahead more than it melts, and a receding glacier is one that melts more than it moves. By definition, all glaciers move, if it is stagnant it is called an icefield. Typically, a glacier advances during the winter and recedes during the summer, but to be technically correct the amount of advance (or receding) should be measured over a full year, or multiple years.

Now for your second question, a glacier is powerful because of the mass. The basic physics formula F=MxA applies here. Just imagine a 100 m thick glacier 3 km long and 400 m wide, that gives you a mass of some 100 million tonnes. Now apply the formula and you've got tremendous force. And that's a fairly small glacier!

Answer 2

I worked at Franz Josef Glacier in New Zealand, It and the nearby Fox Glacier are some of the fastest moving in the world...they were advancing at the time up to 2 meters per day!! (I had the glacier walks people ringing me to say the ropes had to moved back again as the glacier was pushing it over!)....its now retreating..I'm not sure how fast. The reason why its so fast here is the steepness of the valley and the amount of snow/ice at the top of the glacier.

Answer 3

Most glaciers slide downhill only a few feet per day. But since it's a huge mass of ice & rocks several miles long, it's pretty hard to stop.

If a glacier slides into something it can't move, it will split and go around it (on both sides often) or over it.

Answer 4

There are two types of glaciers, continental and alpine. Continental glaciers can be more than a mile thick. Imagine a mile of ice crushing its way down your city street. It might be slow but it's got a lot in its back pocket.

Answer 5

"By 2000, the glacier had sped up to 5.8 miles per year, topping out with the last measurement in spring 2003 of 7.8 miles."