Alan Whittington

Education

Ph.D. in Earth Sciences, Open University 
B.A. in Earth Sciences, University of Cambridge

Research Interests

Dr. Whittington's research interests are in the transport, emplacement and/or and eruption of magma. His group makes high-temperature experimental measurements of rheology and thermal properties of rocks and magmas to understand lava flow emplacement and effusive-explosive transitions on Earth and other planets. His teaching interests are in Volcanology, Rheology of Earth Materials, and Geologic Hazards.

STGS abstract for 9/11/19 

Alan Whittington, UTSA Geological Sciences.

“Flow, blow, or no show? How magma rheology affects volcanic eruptions”

The viscosity of a fluid (viscosity = stress / strain rate) affects how fast it can flow. Magma is a
three-phase mixture of molten rock, crystals and gas bubbles, and often displays rather
complex rheological behavior, but we can describe it simply as an effective viscosity. Even thin
flows of hot basaltic lava, with an effective viscosity similar to ketchup (~100 Pas), can move
rapidly and pose a direct hazard to communities living downslope. Cooler rhyolitic lava, with an
effective viscosity similar peanut butter (~100,000 Pas), typically moves very slowly and forms
flows tens to hundreds of meters thick. Dry magma can be thousands to millions of times more
viscous, and is unlikely to make it to the surface at all before it cools and quenches or
crystallizes.
Upon decompression, water solubility in magma decreases rapidly, causing bubbles to nucleate
and grow. If these bubbles can escape easily from the lava (e.g. the bubbles are large, the lava
is fluid, and there is time for the bubbles to escape), lava fountains and small Strombolian
eruptions result. If the bubbles cannot escape, they grow until the resulting foam fails
catastrophically, producing a large explosive eruption. I will discuss how we measure lava
rheology in the lab and in the field, and some interesting applications of lava rheology to
understanding igneous processes on Earth and other planets.

on