Numerical Simulation of Lava Flows on Some Volcanoes in Japan

Abstract

The present chapter proposes a numerical calculation for simulating the macroscopic movements of lava flows on actual topography of volcanoes and tests it for three recent Japanese eruptions. The topography of the volcanoes as shown on pre-eruption maps was digitized using a grid in which the sampling interval was smaller than the width of the main stream of lava. The flux of lava among meshes is calculated from the steady-state solution of the Navier-Stokes equation for a Bingham fluid flowing due to gravity on an inclined plane. The calculation evaluates temperature change due to cooling by radiation. Viscosity is then estimated using an empirical relationship between viscosity and magma temperature and composition. The effusion rate and the duration of extrusion were estimated from the records of the eruptions. Three lava flows with different chemical compositions were simulated to check the validity of the method: the 1983 Miyakejima lava flows (53-540/0 Si0 2 ), the 1986 Izu-Oshima lava flows (54-58%), and the 1914 Sakurajima lava flows (59-62%). The simulations match fairly well the progress of flow fronts and actual thickness of the lavas. Some discrepancies in inundation area were found at the branches of lava streams and at the margins of main streams. These are largely due to insufficient precision of maps of the pre-eruptive topography and to the size of the sampling interval in the horizontal dimension being large relative to the widths of lava streams.

Himawari-8 infrared observations of the June–August 2015 Mt Raung eruption, Indonesia

“…High-temperature regions on the surface are believed to cool down quickly due to the occurrence of effective radiative heat loss from the surface following effusion (Dragoni 1989;Ishihara et al 1990;Oppenheimer 1991). A simplified estimate indicates that the surface of a lava flow with a temperature of 1100 °C can drop to a temperature of 350 °C in 3 h through radiative cooling (Yamashita and Miyamoto 2009).…”

VTFS project: Development of the lava flow simulation code LavaSIM with a model for three‐dimensional convection, spreading, and solidification

“…[47] Ishihara et al [1989] carried out computer simulations of the LBI, LBIII and LCI lavas using a two-dimensional code, and reproduced the area inundated by lava within À9% to +37% for LBIII, and reproduced the flow length to within 300 m for LCI. Their results also showed qualitative similarities for the spatial distribution and thickness of LBIII and LCI.…”

“…The resolution is 0.1 m for the elevation data and 0.1 degrees for both of the angle data sets. The maximum area error due to the finite horizontal dimensions of the cells (10 m) is estimated roughly at 2.3% for the LBIII lava flow (with an average width of 420 m, calculated from the flow length and area [Ishihara et al, 1989]). On the other hand, the maximum area error is 26% for the LCI lava flow which has Figure 14.…”

“…An unforked lava flow along the direction of the maximum slope, and a distance to the stopping point are obtained. Prior to FLOWGO, a twodimensional explicit scheme was developed by Ishihara et al [1989] and later refined by Miyamoto and Sasaki [1998]. The code made explicit calculations possible because the pressure term was replaced by the hydraulic head of the lava liquid level and the ground inclination.…”

Preliminary assessment for the use of VORIS as a tool for rapid lava flow simulation at Goma Volcano Observatory, Democratic Republic of the Congo

“…For lava flows, a wide diversity of both probabilistic and deterministic simulation models exist in the volcanological literature (e.g. Crisci et al, 1986Crisci et al, , 1997Ishihara et al, 1989;Wadge et al, 1994;Kuauhicaua et al, 1995;Felpeto et al, 2001;Favalli et al, 2005;Damiani et al, 2006) and offer different degrees of accuracy, depending on the mathematical methods used to make calculations and the input parameters considered. Unfortunately, most of these models only exist in the scientific literature and their source codes are not freely available.…”