Two types of lava fields and the mechanism of their generation

Abstract

Two types of lava fields, elongate and compact, are generated by two types of discrete lava flows that are designated as wide and narrow in this paper. The width of a wide flow considerably exceeds its thickness, the converse being true for a narrow one. Wide flows produce relatively narrow elongate lava fields, while narrow ones give rise to wider and compact lava fields of relatively smaller area and greater thickness, which is related to peculiarities in their dynamics causing branching and greater heat losses in such flows. Exact analytical formulas have been derived to relate the rate of lava in a flow to the flow geometry and lava rheology for idealized models of both flow types; a combination of these yields the approximate relationships for actual flows. We have found conditions for the generation of narrow flows showing strongly nonlinear behavior, which produces the peculiar features of the lava fields they create. Examples of lava fields generated by narrow flows from lateral vents on Klyuchevskoi Volcano are given. The conditions for their generation are more closely fulfilled in the upper part of the volcano’s cone. It is hypothesized that such an arrangement of lava fields may facilitate slope instabilities and enhance the likelihood of major landslides.