Lithology: The Fourfold Scheme

Abstract

There are three types of natural rocks : igneous, sedimentary, and metamorphic. Spain contains a good representation of the three, and there are certain places which are archetypical of the planet, including several “type locations.” So, for instance, the Canaries have both AA and pahoehoe lava (Hawaii only has the latter); roads in the north of Castile have roadcuts revealing some neat strata from the Miocene; and metamorphic rocks characterize the landscape and the buildings of parts of Guadalajara (“black villages,” owing to the color of the slate used for roofing) and Cáceres (shire of “Las Hurdes”). Lithology has played a very important role in the selection of construction sites, not only for tectonic reasons but also for other practical reasons. A good example is the location of Mahon in Menorca . The southern shore, made up of limestone and sandstone and where freshwater could be found, was chosen for the settlements , while the northern, steeper and sheer rock, remained unoccupied.