TY - JOUR

T1 - Rheological properties of basaltic lavas at sub-liquidus temperatures: laboratory and field-measurements on lavas from Mount Etna.

AU - Pinkerton, Harry

AU - Norton, G. E.

PY - 1995/11

Y1 - 1995/11

N2 - Models of many magmatic processes require accurate data on the rheological properties of lava at sub — liquidus temperatures. Laboratory measurements of the rheological properties of basalts erupted on Mount Etna in 1983 were made at various crystal concentrations in a specially designed furnace using a Haake Rotovisco viscometer attached to a spindle designed to eliminate slippage at the melt-spindle interface. Measurements were made at strain rates between 0.3 and 5 s−1 over the range of eruption temperatures on Mount Etna (1084–1125 °C). At temperatures above 1120 °C, the 1983 lava behaves as a Newtonian fluid. At lower temperatures, the lava is a thixotropic, pseudoplastic fluid with a maximum yield strength of 78 Pa at a temperature of 1087 °C. In view of its low yield strength over this temperature range, the Theological behaviour of the lava approximates to that of a power law fluid. Apparent viscosities at unit shear strain rates increase from 150 Pa s at 1125 °C to 3000 Pa s at 1084 °C. Unit strain rate apparent viscosities measured in the field using a rotating vane viscometer range from 1385 Pa s to 1630 Pa s. These values are in close agreement with those measured at the same temperature in the laboratory and with those calculated theoretically from the physico-chemical properties of the lava.

AB - Models of many magmatic processes require accurate data on the rheological properties of lava at sub — liquidus temperatures. Laboratory measurements of the rheological properties of basalts erupted on Mount Etna in 1983 were made at various crystal concentrations in a specially designed furnace using a Haake Rotovisco viscometer attached to a spindle designed to eliminate slippage at the melt-spindle interface. Measurements were made at strain rates between 0.3 and 5 s−1 over the range of eruption temperatures on Mount Etna (1084–1125 °C). At temperatures above 1120 °C, the 1983 lava behaves as a Newtonian fluid. At lower temperatures, the lava is a thixotropic, pseudoplastic fluid with a maximum yield strength of 78 Pa at a temperature of 1087 °C. In view of its low yield strength over this temperature range, the Theological behaviour of the lava approximates to that of a power law fluid. Apparent viscosities at unit shear strain rates increase from 150 Pa s at 1125 °C to 3000 Pa s at 1084 °C. Unit strain rate apparent viscosities measured in the field using a rotating vane viscometer range from 1385 Pa s to 1630 Pa s. These values are in close agreement with those measured at the same temperature in the laboratory and with those calculated theoretically from the physico-chemical properties of the lava.

U2 - 10.1016/0377-0273(95)00018-7

DO - 10.1016/0377-0273(95)00018-7

M3 - Journal article

VL - 68

SP - 307

EP - 323

JO - Journal of Volcanology and Geothermal Research

JF - Journal of Volcanology and Geothermal Research

SN - 0377-0273

IS - 4

ER -