We recently awarded a 3-year $160,000 grant from the NASA Mars Fundamental Research Program entitled "Mars Lava Flow Surface Morphology: An Avenue for Answering Fundamental Questions Regarding the Rates and Styles of Volcanism". The research project has 3 tasks, and each task has a set of laboratory, field and modeling work designed to shed light on a particular variable that affects a lava flow surface:

A.  The Role of Underlying Topography on the Development of Surface Features

1.  We will run a series of experiments where we pump polyethylene glycol wax (PEG) over simulated hummocky topography (inverted watch glasses) to determine the effect of underlying topography on the appearance of a flow surface.

Above: Undergraduate student Tessa Krueger observing an analog PEG flow in the Waxworks Lab at Arizona State University.

2.  We will use a high-precision GPS and laser rangefinder to measure the topography of an older lava flow surface in Hawaii, then repeatedly resurvey the area as new lava flows over the old surface.  The repeated profiles should allow us to study the effect of topographic lows and highs on the final surface of the flow, as well as provide us with information on the details of flow growth.

3.  We will modify some previous work by Jon Fink and Ross Griffiths by modeling the effect of underlying topography on flow morphology.  Fink and Griffiths proposed that morphology is linked to a dimensionless parameter, psi, which relates the timescale of cooling to that of advection.  We will add in a roughness coefficient that accounts for the irregular surfaces encountered by some flows.

B. The Nature of Lava Flow Interior Structure and its Influence on Morphology

1.  We will run of series of PEG experiments to document the development of viscous fingers in flow interiors.  Viscous fingers a a result of instabilities in the flow interior, and can be studied in a controlled environment such as the Waxworks lab.  We view the flow interior from the underside of the flow tank, and sequentially extrude PEG of different colors to image the pathways that exist in the flow interior. We can then relate the nature of the flow interior to the resulting surface appearance.

Above: A PEG flow viewed from the underside.  Arrows point to viscous fingers that developed in the flow interior.

2.  We will use a FLIR Thermascan camera to image the surface of an actively developing flow field in order to determine where flow paths exist beneath the crust.  Subsurface flow paths should keep the flow surface hotter than the surrounding areas, and we hope to create a map of the flow surface temperatures and relate any patterns to processes occurring beneath the flow surface.

3.  We are investigating models of Saffman-Taylor instabilities to determine the size and shape of potential viscous fingers in lava flow interiors, and use this information to assess their affect on flow morphology.

C.  The Role of Composition and Extrusion Rate on Flow Morphology

1. Some lava compositions have received more attention in the terrestrial literature than others with respect to the development of surface morphologies.  We will investigate the surfaces of lava flows with intermediate compositions (andesite, basaltic andesite) to better understand how these flow surfaces develop.  We will first mimic their formation in the lab using a kaolin slurry over simulated topography.

2.  We will also measure the block size distributions on intermediate flows in the western US to determine how their surfaces differ from more mafic and more silicic flows.  The blockiness of a lava flow surface can be measured remotely using satellite imagery, and is therefore an important avenue for studying planetary flows.

II. Fractal Dimensions of Evolved Lava Flows

We are measuring the fractal dimensions of many evolved flows in the western US to determine whether or not they exhibit fractal behavior, and whether their fractal dimensions are diagnostic of composition.  We are also measure the fractal dimensions of suspected evolved flows on other planets for comparison.

III.  Steep-sided domes on Venus

The surface of Venus is dominated by volcanic landforms, including extensive flow fields, sinuous channels, and a wide range of volcanic edifice styles. One of the most distinctive edifice types on Venus is the steep-sided dome, first detected in Magellan images of an area to the southeast of Alpha Regio. These features were informally called 'pancake' domes, due to their flat-topped, steep-sided appearance. Venusian domes are similar to terrestrial silicic domes as both are generally circular and have steep sides. However, terrestrial domes are smaller and tend to have extremely rough surfaces with different distributions and types of surface.

Previous studies have shown that compositional determinations are non-unique when based on gross morphologic properties; in other words, a range of compositions from basaltic to rhyolitic could explain dome morphology. However, features such as ridges and fractures on dome and lava flow surfaces can be used to understand their physical properties, emplacement, and cooling behavior. In order to further understand the origin of steep-sided domes, we are conducting a detailed study of the surface morphology of venusian steep-sided domes in full resolution Magellan data. We will supplement these data with models of lava flow crust formation under venusian conditions to better understand the formation of these features. We recently published a  couple of papers on our work in the Journal of Geophysical Research - Planets (Stofan et al., 2000;Plaut et al., 2004).

Back