granite

Granite cliffs alongside deep fjord waters in Norway. The hard granite was carved out by powerful glaciers. Today, due to the warming influence of the Gulf Stream and the salt content of the water, the Norwegian fjords are ice-free all year.

Altered granite through a polarized microscope. Granite is the most common type of intrusive rock.

Granite is a hard, igneous rock that produces a landscape of high ground, and wet, waterlogged areas. Outcrops of granite like this one can be seen throughout Dartmoor, in southwest England, and particularly on hilltops, where tors have been formed.

Granite is a hard, igneous rock. However, it is eroded by freeze-thaw weathering and by hydrolysis (a form of chemical erosion). The granite is broken down most effectively where there are more joints or cracks in the rock, and it is most resistant where there are fewer joints. The unweathered rock forms a tor, an upstanding, isolated mass of rock, like this one on Dartmoor.

Granite is a hard, resistant rock, but when it is subjected to weathering it may be broken down to produce fine china clay (kaolin). Granite contains many minerals, including feldspar. When acid reacts with feldspar, it can produce kaolin. Normal rainfall is naturally acidic, and water that percolates through the soil also picks up organic acids that help to dissolve the granite. In this picture, unweathered granite is seen as solid rock, surrounded here by weathered rock.

Granite is an igneous rock, normally found deep in the earth's crust and made of crystals formed from the cooling of molten magma. It is sometimes exposed at the surface where the sedimentary rock, such as sandstone, has been eroded. Surface concentrations of Cornish granite can be found on the highlands of Land's End and Bodmin Moor.

Lichen-covered granite stones have been piled together to make a boundary wall in western Ireland. Fields in this part of the country are bare and rocky, and the stones must be lifted in order to cultivate the fertile soil.

Coarse-grained intrusive igneous rock, typically consisting of the minerals quartz, feldspar, and biotite mica. It may be pink or grey, depending on the composition of the feldspar. Granites are chiefly used as building materials.

Granite is formed when magma (molten rock) is forced between other rocks in the Earth's crust. It cools and crystallizes deep underground. As it cools slowly large crystals are formed. Granites often form large intrusions in the core of mountain ranges, and they are usually surrounded by zones of metamorphic rock (rock that has been altered by heat or pressure). Granite areas have characteristic moorland scenery. In exposed areas the bedrock may be weathered along joints and cracks to produce a tor, consisting of rounded blocks that appear to have been stacked upon one another.

Jointing of the granite occurs when pressure reduces on the sheets underground following the erosion of the rock layers above. The sheet springs up into a gentle dome, and joints and cracks occur. These are opened up or fall away under weathering processes such as chemical weathering and exfoliation.