Valley formation by groundwater seepage, pressurized groundwater outbursts and crater-lake overflow in flume experiments with implications for Mars
Valley formation by groundwater seepage, pressurized groundwater outbursts and crater-lake overflow in flume experiments with implications for Mars
复制标题
水槽实验中地下水渗漏、加压地下水突出和火山口湖溢出形成的山谷对火星的影响
DOI：
10.1016/j.icarus.2013.12.026
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发表时间：
2014
期刊：
影响因子：
3.2
通讯作者：
M. Kleinhans
中科院分区：
文献类型：
--
作者：
W. Marra;L. Braat;A. Baar;M. Kleinhans
火星上的河谷遗迹揭示了火星表面以前存在水。然而，水的来源和水文环境并不总是清楚的，特别是在地球上罕见的山谷类型中，我们对所涉及的过程的了解有限。我们调查了三个水文方案的山谷形成在火星上：静水地下水渗流，释放加压地下水和火山口湖溢出。利用物理模拟实验室实验和数值水文模拟，我们定量研究了形态发展和过程中涉及的通道形成，导致这些不同来源的水在松散的沉积物。我们的研究结果表明，出现的山谷渗透地下水的溯源侵蚀形成相对缓慢的河流运输发生在一个通道比山谷小得多。承压地下水释放通过流态化过程在渠首形成特征源区。在超岩石静压力的情况下，这个头部由一个坑组成，并且可能具有小的径向通道和塌陷特征。火山口-湖泊溢流事件形成的河谷在边缘侵蚀和流量增加的逃逸过程中迅速发育。在火山口流出点的谷头有一个收敛的扇形，和边缘的快速切割留下阶地和崩溃的功能。如果考虑到实验尺度和火星表面的岩性特征，实验中观察到的形态要素可有助于确定火星上的形成过程。这些形态特征可能揭示了相关的水文环境和形成的时间尺度的一个山谷。对沉积物运移形成时间尺度的估计最好是根据地下水渗漏谷的最终通道尺寸和加压地下水释放和火山口湖溢流谷的谷尺寸。我们的实验表明，不同的水源在完全不同的时间尺度内形成了大小相似的山谷。
Remains of fluvial valleys on Mars reveal the former presence of water on the surface. However, the source of water and the hydrological setting is not always clear, especially in types of valleys that are rare on Earth and where we have limited knowledge of the processes involved. We investigated three hydrological scenarios for valley formation on Mars: hydrostatic groundwater seepage, release of pressurized groundwater and crater-lake overflow. Using physical modeling in laboratory experiments and numerical hydrological modeling we quantitatively studied the morphological development and processes involved in channel formation that result from these different sources of water in unconsolidated sediment. Our results show that valleys emerging from seeping groundwater by headward erosion form relatively slowly as fluvial transport takes place in a channel much smaller than the valley. Pressurized groundwater release forms a characteristic source area at the channel head by fluidization processes. This head consist of a pit in case of superlithostatic pressure and may feature small radial channels and collapse features. Valleys emerging from a crater-lake overflow event develop quickly in a run-away process of rim erosion and discharge increase. The valley head at the crater outflow point has a converging fan shape, and the rapid incision of the rim leaves terraces and collapse features. Morphological elements observed in the experiments can help in identifying the formative processes on Mars, when considerations of experimental scaling and lithological characteristics of the martian surface are taken into account. These morphological features might reveal the associated hydrological settings and formative timescales of a valley. An estimate of formative timescale from sediment transport is best based on the final channel dimensions for groundwater seepage valleys and on the valley dimensions for pressurized groundwater release and crater-lake overflow valleys. Our experiments show that different sources of water form valleys of similar size in quite different timescales.