Cataldo Vincenzo, Williams David A, Dundas Colin M, Keszthelyi Laszlo P
School of Earth and Space Exploration, Arizona State University, Tempe, Arizona, USA.
Astrogeology Science Center, U.S. Geological Survey, Flagstaff, Arizona, USA.
J Geophys Res Planets. 2015 Nov;120(11):1800-1819. doi: 10.1002/2014JE004761. Epub 2015 Nov 21.
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 and average flow thicknesses of 20 and 30 m, the duration of the eruption varies between 11 and ~37 days. The erosion of the lava flow substrate is investigated for three eruption temperatures (1270°C, 1260°C, and 1250°C), and volatile contents equivalent to 0-65 vol% bubbles. The largest erosion depths of ~3.8-7.5 m are at the lava source, for 20 m thick and bubble-free flows that erupted at their liquidus temperature (1270°C). A substrate containing 25 vol% ice leads to maximum erosion. A lava temperature 20°C below liquidus reduces erosion depths by a factor of ~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 ~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 (35-100 m). We conclude that thermal erosion does not appear to have had a major role in excavating Athabasca Valles.
阿萨巴斯卡谷溢流玄武岩是火星上最年轻（<50 Ma）且保存最完好的溢流熔岩流之一，其就位过程可能较为混乱。威廉姆斯等人[2005]的熔岩热侵蚀模型已应用于我们所称的“近端阿萨巴斯卡”，即阿萨巴斯卡谷75公里长的上游部分。对于5000和7500立方千米的就位体积以及20和30米的平均流厚，喷发持续时间在约11至约37天之间变化。针对三种喷发温度（1270°C、1260°C和1250°C）以及相当于0 - 65体积%气泡的挥发物含量，对熔岩流基底的侵蚀进行了研究。对于在液相线温度（1270°C）喷发的20米厚且无气泡的熔岩流，最大侵蚀深度约为3.8 - 7.5米，位于熔岩源处。含有25体积%冰的基底会导致最大侵蚀。比液相线温度低20°C的熔岩温度会使侵蚀深度降低约2.2倍。如果熔岩流粘度随熔岩中气泡含量增加而增大，30 - 50体积%气泡的存在会使侵蚀深度比无气泡熔岩的侵蚀深度低约2.4倍。基底中25体积%冰的存在会使侵蚀深度增加1.3倍。然而，与就位体积和流持续时间限制相符的模拟侵蚀深度远小于河道深度（约35 - 100米）。我们得出结论，热侵蚀似乎在阿萨巴斯卡谷的挖掘过程中未起主要作用。
