Write a brief note on Geomorphic Cycle in a Volcanic Cone



After a cone has been built by an eruption, the period of following quiet witnesses the development of consequent radial drainage and according to O.D. von Engeln this is the stage of youth in the erosional cycle that has started on the cone.

Although the cones are generally built of pyroclastics and should be soon eroded down, this does not happen because of the great permeability of the cinders and the durability of the siliceous fragments wherever they occur. The cones, therefore, remain geomorphically symmetrical, particularly if the region happens to be arid marked by limited chemical weathering. The surface takes shape on the cinder cones only after the slow process of chemical weathering has been able to produce finer particles that close the pores of cinders.

The youth is marked by roughly equal streams in the beginning. Later integration follows resulting in a small number of deeper and wider valleys, called barrancas. This phenomenon is seen in the Hawaii where the consequents form highly deep and broad canyons, the intervening divides being well-marked steep ridges.

If the cone is a strato-volcano or composite volcano composed partly of cinder and partly of lava layers, the topography becomes differentiated on this account. Subsequent annular drainage becomes seated on the yielding cinder layers, whereas the resistant lava layers form ridges, including dyke ridges. Triangular plateaus built out of lava beds are called planezes in French, as in Auvergne. When the triangular plateaus are separated by erosion from the central region of the cone, they become mesas.