ABSTRACT
Erosional landforms characteristically associated with volcanoes are distinctive and differ from landforms produced by same processes in other settings. Volcanoes are commonly linked with faults and earthquakes, and they may tell us much about major structural features of earth. In the North Atlantic, there is a mid-Atlantic ridge with young rocks and some active volcanoes, and rocks of sea floor get older towards both North America and Europe. In brief, the plate tectonic hypothesis suggests that the earth is divided into a number of plates, and most of the action, including volcanic activity, takes place at plate boundaries. Pyroclastic rocks are especially common amongst volcanoes of siliceous composition such as andesites and even more siliceous rhyolites. If a set of such dykes intrude porous rocks they divide volcanic mass into a number of separate groundwater compartments, each like a bucket of sand, with the bucket representing the dykes and the sand representing the porous rock in groundwater compartment.
