The landscape of granite

The landscape of granite		Back to the home page

The granite cliffs that were sculpted during de-glaciation are the main attraction of Stångehuvud. Here the Bohus granite has its southernmost presence on land. The granite in the area of Lysekil has been determined to have an age of 920 million years. Coarse-grained granite is the kind that is mostly in evidence when you are walking in the Stångehuvud area. Fine examples of coarse-grained granite are visible at the steps when walking on the path between Stångholmesund and Kramkistesund. In the eastern part of Stångehuvud there is another granite type. This is the more "normal", medium-grained version. In the hillside about 75 metres to the west of Gullmarsvallen there is a sharp delineation between the coarse-grained and the medium-grained granite types. Such a clear distinction between different types of granite is seldom seen in the province of Bohuslän. At Galleberget, in the north of Stångehuvud, the medium-grained granite type is predominant. *Pegmatite veins crisscross* Typical for the granite landscape in Stångehuvud is that it is crossed by paths of a different rock type, pegmatite. In some places, you can follow these paths for hundreds metres. Pegmatite can be said to be a granite with very large crystals. The rock was formed in the latter part of the period when the granite magma was solidified. Gradually tensions occured in the rock, resulting in cracks, usually one or a few decimetres wide. To these cracks were drawn water-rich solutions from the ambient, not yet hardened granite, which crystallized slower than the ordinary granite. The result was pegmatite which has the same mineral composition as granite, but with much larger crystals. Stonemasons used to call these pegmatite veins "cat" or "cat stripes". These veins were, for obvious reasons, not very popular among the stone workers, because it was not worthwile breaking granite in places with numerous pegmatite veins. A very special formation of pegmatite has given its name to the so called Lejonpallen, which is marked on the map of Stångehuvud from 1892. *The inland ice has formed the landscape* The pristine parts of the mountain landscape of Stångehuvud got their present appearance during the last deglaciation almost 14 000 years ago. The ice - nearly one kilometre thick at most - was moving slowly, mainly in the direction northeast to southwest. Like a giant plane, it slid forward and levelled the mountain. When the climate became warmer, numerous tunnels with meltwater were created under the ice in the area of contact with the granite. Under very high pressure and mixed with gravel, stone, blocks etc, the melt water was forced upward and polished the granite.	Read more about the granite: How was the Bohus granite formed? What consists the Stångehuvud granite of and what gives it the red colour? *Pegmatite veins of coarse-grained quartz, feldspar and mica are typical in the granite cliffs of Stångehuvud.*

Boulders from far and near

Boulders that have loosened from the surrounding rock surface may be seen at several places in the Stångehuvud area. The only larger beach consisting of naturally formed boulders is found in the northern part of Kramkistesund. Here finer material has surged with the passage of time and rounded boulders have been left behind. Many of these have been transported to Stångehuvud over great distances when the inland ice melted.

Many boulders consist of granite, others of various kinds of veined gneiss, that is to say gneiss where you can distinguish different layers on top of each other. Some gneiss boulders have hints of darker minerals, such as amphibole.

Near Valhall in the western part of Storklyftan there are some impressive boulders of coarse-grained granite which are rather sharply angular. They are seven to eight meters long and have probably broken off from rocks in the surrounding area when the ice was melting.

One interesting boulder that moved to Stångehuvud and that strongly differs from the common bohus granite is divided into two halves, which now lie to either side of a small path, some 50 meters or more to the west of Gullmarsvallen (see photo on the right). For those interested in geologically this boulder is well worth a visit. The boulder is more than one meter high and of a rock type called breccia.