Nature's experiments: retreating glaciers

The retreat of glaciers opens new land. The rapidity by which glaciers melt in some regions offers a test case for how rapid vegetation can follow and secure the exposed ground.

As an example, look at the greening of the landscape in the former bed of the Rhone glacier in the Swiss Alps. In 1860, the glacier almost reached the Hotel to the left. The first 1-2 km of the released ground have been kept open for cattle grazing. The middle zone already shows a tall stature Larix forest. The bare rock released most recently from ice offers little space for vegetation.

At a constant rate of glacier retreat, what maximum age might the trees have?

Rhone glacier
1 - Rhone glacier and forefield