Re: Can mountains shrink? If so, what causes them to shrink?

The short answer is no. The long answer is yes, that is mountains do get smaller over time as they are worn down by forces of erosion; wind,water,freezing,thawing and chemical reactions. Wind acts as a kind of sand blaster on a mountain, rain slowly washes material away and can act as a solvent to chemically dissolve rocks like limestone or by merely soaking into the rock the freeze / thaw cycle of the changing seasons can be a very strong erosive force.

The important thing to remember is the time scale, erosional processes generally take thousands of years, although certain catastrophic events like a landslide can happen in minutes. A landslide can occurr for many reasons, an earthquake or the sudden flooding of water along an already weakened portion of a mountain for example. One case occurred around the turn of the century at the town of Frank, Alberta, Canada. An entire side of a mountain next to the small town of Frank slid off in a disastrous avalanche.The entire town was destroyed, and the mountain that caused the slide was definitely smaller afterwards. In the case of volcanic mountains, like Mt. St. Helens, the molten rock material or magma that is within the mountain, which was responsible for its creation and subsequent eruptions, can be thought of as being part of an underground "plumbing" system. The solid lava dome that now forms the top of this mountain is carefully measured to see how quickly its swelling due to the force of the magma within. On occaision, a volcanic dome in an active area will be seen to swell and also to subside or shrink down in size due to the processes deep underground in the magma reservoir. This really isn't understood very well yet, but if the swelling of the dome is continuous its usually taken as a very good sign that an eruption can be expected shortly.

Mountains as a rule last a very long time, but that does not mean forever. Older mountains are usually smaller than younger ones because of their longer exposure to erosion.