FRAGILE ALPINE ENVIRONMENTS  

Sandstone

Sanstone is a detrital sediment made up of the detritus of erosion. Clastic sediments are more abundant than chemical precipitates, because mechanical erosion is widespread all over the earth and much of the crust is composed of silicates that are relatively insoluble at the temperatures and pressures present on the at the earth’s surface. Sand could have been deposited, for example, by a river in a delta or by wind, forming a dune. The grain size of sand varies between about 2 to 0.1 mm.

Limestone

Limestone is a chemical or biogenic sediment and accounts for a major proportion of the carbon dioxide stored in the earth’s crust. If this carbon dioxide were somehow released, it would significantly change the composition of the atmosphere and cause the surface temperature to heat up. Limestone can consist of reef organisms or carbonate shells, but is mainly formed of the mineral calcite, precipitated out of the water in a lake, ocean or river and then deposite

Conglomerate

A conglomerate is a clastic sediment (from the Greek klastos, to break), carrying the earmarks of mechanical transportation and deposition of the debris of erosion. The abrasion during transportation rounds the particles. A conglomerate has coarse clasts (e.g. gravels or stones) in a fine matrix, which consists mainly of small fragments. If the clasts are equally large, but angular, the rock is a breccia and not a conglomerate.

Granite

A coarse-grained, intrusive igneous rock composed of quartz, feldspar and micas with a high content of silicate minerals. Granite is widespread in the continental crust. Prime examples are the Yosemite National Park (U.S.) or the Grimsel region (Switzerland). A granite landscape generally has a smoother and more massive expression than those composed of other rock types, e.g. such as limestone. Granite weathers slowly in temperate regions, but relatively fast in tropical regions.

Basalt

A fine-grained, dark igneous rock composed largely of feldspar and pyroxene. Basalt is the most abundant volcanic type. The depositions of shield volcanoes like the Hawaiian volcanoes are basaltic.

Andesite

This rock type is related to explosive volcanism, e.g. to the stratovolcanoes of the Andes (it is also named for the Andes) in South America or the Cascade Range (U.S.). It consists of fine minerals (e.g. amphiboles), which are situated in a fine-grained matrix.

Gneiss

A high grade of metamorphism with coarse grains and pronounced foliations, with layers of micaceous minerals segregated from layers of minerals such as quartz is called a gneiss (pronounced “nice”, from the German word gneisto, meaning to sparkle). It is formed by metamorphism, the process by which pre-existing rocks are altered by temperature and pressure. One can determine what the rocks where before they were altered (e.g. the metamorphic rock marble, for instance, now all coarsely crystalline calcite, was once a limestone).