Stone run

Boulders are large accumulations of stone blocks with diameters almost exclusively about 20 cm on slopes. They are due to their heat, drought and the lack of fine material, a special habitat for animals and plants. Some, particularly used as a tourist boulders are commonly referred to as rock oceans or seas block.

Boulder fields caused by strong weathering, however, forms only a little gravel and sand. This means that the blocks of a very hard material (eg granite or quartzite ) are made and the original rocks are crushed mainly by frost shattering of their fractures.

Unlike the scree

Because of this mode of origin lacks the boulders - in contrast to rubble or scree ( talus Geol ) - the proportion of gravel and sand. This means that water can drain quickly and also in wehter humus will soon be washed away. On the other hand, there are rock crevices or ledges, in which fine soil can accumulate. Therefore, the habitats are very different, so that a completely different vegetation present. It often finds himself doing almost no plant life on the block heap except algae, mosses and lichens.

Since boulders piled solely by gravity, they have, in contrast to alluvial water block seas to a higher pitch. Because of this and because of the large, irregular spaces between the individual blocks is committing such Halden dangerous; am Semmering (see first picture) it has already led to several mountain accidents.

Some boulders are the remains of a former rock glaciers, such as the sheep stone.

Icing

In some cases, there is another peculiarity, which leads to even more specialized habitats: In the block heap is a greater amount of ice that can also be a feature of the former rock glacier. In winter there is a flow of air through the heap block, in which the cold air flows down and heated at the top of the heap flows. In this case, the interior of the heap cools and the amount of ice is growing. In summer, the air flow is reversed: The warm air enters at the top of the heap in one, cools and flows at the bottom of the heap again. This cold air outlets are partly to notice much, if can hold up in the summer ice on these withdrawals, long time. To ensure that this effect is possible that differences in temperature must be as large as possible. Therefore, the effect in spring and autumn makes little noticeable. In addition, the ice makes its latent heat to both the heat storage and to maintain a substantially constant temperature in the interior of which the possible differences in temperature increases to the outside.

The heat transport and heat storage lead to two further specific habitats: At the top of the heap block is particularly heat- loving plants can hold, since this area is kept free of ice by frequently leaving the warmer air in the winter. In the summer it is warmer air is sucked in here, so the rocks are stronger and more heat at a greater depth and thus in the night warmer than its surroundings.

At the bottom of the heap block flows in the summer of cool moist air. Due to the constant moisture can form so-called condensation Moore here. The growth of Sphagnum and other mosses is very rich due to the humidity. Also, can claim alpine plants, which were otherwise displaced after the Ice Age from most parts of Central Europe by the cooler air.