Paleovolcanology

the branch of geology that studies the volcanic activity of past geologic epochs. Paleovolcanology is principally concerned with the formation of ancient volcanoes (the types of central structures, calderas, remnants of volcanic shields) and their roots (stocks, necks, pipes, and other channels through which magma rose to the earth’s surface). The roots, which extend deep into the earth, can be directly studied in the eroded cuts of ancient folded structures; such study is impossible with present-day volcanoes.

Volcanic formations and the accumulations associated with them—lavas, pyroclasts, and the products of redeposition— together make up volcanogenic deposits. An integral part of paleovolcanologic research is study of the composition of volcanogenic materials and the laws of their occurrence in time and space. The general issue of magmatism and tectonics is very pertinent in the branch of paleovolcanology that examines the development of volcanic activity in past geological epochs and the factors giving rise to volcanism. This aspect of paleovolcanology touches on the origin and formation of the volcanic belts on the continental margins. It also touches on these questions in reference to the areas of ancient volcanism in continental masses and on the ocean floor.

Paleovolcanology is based on the methods of actualism and comparative historical analysis. The techniques of structural, facies, and formation analysis are used to study the structure of ancient volcanoes. Optical techniques are used to determine the composition of the products of ancient volcanic activity, as are the techniques of chemical and thermal analysis. Other modern physics and chemistry research methods are used as well.

Ancient volcanoes are mentioned in the classical period by Pythagoras and Strabo and during the Middle Ages by Maggioli, Hooke, and others. M. V. Lomonosov wrote of the role of volcanoes in the creation of ores. N. Desmarest provided the first descriptions of the ancient volcanoes in the Auvergne region of France in the late 18th century. In 1897, A. Geikie’s Ancient Volcanoes of Great Britain was published. The Soviet geologists F. Iu. Levinson-Lessing and A. N. Zavaritskii have studied ancient volcanic activity.

Paleovolcanologic research is very important in paleogeo-graphic reconstruction. It also enables specialists to solve many practical problems in searching for useful minerals that result from volcanic activity (ores of copper, gold, silver and tin).