科研之友
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摘要
The Athabasca Valles flood lava is among the most recent (<50 Ma) and best preserved effusive lava flows on Mars and was probably emplaced turbulently. The Williams et al. (2005) model of thermal erosion by lava has been applied to what we term "proximal Athabasca," the 75 km long upstream portion of Athabasca Valles. For emplacement volumes of 5000 and 7500 km(3) and average flow thicknesses of 20 and 30 m, the duration of the eruption varies between similar to 11 and similar to 37 days. The erosion of the lava flow substrate is investigated for three eruption temperatures (1270 degrees C, 1260 degrees C, and 1250 degrees C), and volatile contents equivalent to 0-65 vol% bubbles. The largest erosion depths of similar to 3.8-7.5m are at the lava source, for 20m thick and bubble-free flows that erupted at their liquidus temperature (1270 degrees C). A substrate containing 25 vol% ice leads to maximum erosion. A lava temperature 20 degrees C below liquidus reduces erosion depths by a factor of similar to 2.2. If flow viscosity increases with increasing bubble content in the lava, the presence of 30-50 vol% bubbles leads to erosion depths lower than those relative to bubble-free lava by a factor of similar to 2.4. The presence of 25 vol% ice in the substrate increases erosion depths by a factor of 1.3. Nevertheless, modeled erosion depths, consistent with the emplacement volume and flow duration constraints, are far less than the depth of the channel (similar to 35-100 m). We conclude that thermal erosion does not appear to have had a major role in excavating Athabasca Valles.
- 出版日期2015-11
