850 research outputs found
The influence of surface clinker on the crustal structures and dynamics of 'a'ā lava flows.
No full textSurface structures on 'a'ā and blocky lavas reflect the internal flow dynamics during emplacement and also influence the dynamics of developing flows. To investigate the effects of brittle, clinkery 'a'ā flow crusts on flow dynamics and surface structures, we conducted sand and silicone laboratory experiments that simulated the advance of lava into a preexisting channelized flow with a surface crust. Experiments carried out with relatively thin crusts produced apparently ductile surface deformation structures, while thick crusts behaved dominantly in a brittle manner. Increased crustal thickness led to increased strength under compression but favored more disruption under tension, as the flow core welled up through tensile fractures, entraining crustal material. At lava flow fronts, upwelling and entrainment would increase heat losses by radiation and advection, respectively, resulting in a positive‐feedback cooling loop. Fracturing caused heterogeneous crustal distribution near the flow front, which resulted in lobate flow advance, despite the absence of the viscoelastic layer that has previously been inferred as the primary control on flow advance and lobe formation. We therefore conclude that the influence of a purely brittle crust on the dynamics and surface morphologies of lava flows is more significant than often thought. All of the surface structures produced in the experiments have been observed on lavas or glaciers and many also on landslides and debris flows, suggesting the results can assist in the understanding of a range of natural flows
A simulator to optimize the experimental set-up for elasto-plastic material characterization
No full textA procedure for specimen optimization applied to material testing in plasticity with the virtual fields method
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Habitability of lava tubes on the Moon and Mars: lessons from Earth
No full textThe main goal of our study was to begin to learn more about the physical and geological reality of lava tubes on Earth, specifically with respect to their habitability. Our objectives focus on two issues of central relevance to assessing the potential habitability of lava tubes on Earth, and by extension on the Moon and Mars: 1) Geotechnical characteristics: How accessible and safe are lava tubes? What makes some lava tubes experience collapse? 2) Relation to ice: Why, when and how does ice occur and evolve in lava tubes? Approach and Findings. 1) To begin surveying the geotechnical characteristics of lava tubes, we carried out a review of the published technical literature on the topic. Our finding is that while there is an abundance of archaeological and historical reports and maps documenting the access, exploration, investigation, use, and occupation of lava tubes, including many anecdotal mentions of collapse features inside lava tubes, there are essentially no published quantitative studies of the geotechnical properties of lava tubes using modern standard geotechnical metrics. 2) To begin examining the relationship between lava tubes and ice, we carried out a field investigation of the Lofthellir Lava Tube Ice Cave in Iceland in which massive ice is known to exist. Our field observations suggest that the ice inside Lofthellir is predominantly meteoric in origin (water from atmospheric precipitation or condensation) rather than from volcanic venting. In other words, the water inside the cave came mostly, if not exclusively, from “above”, not “below”. We also report two important new findings: a) Underground micro-glaciers are recognized for the first time; they form in the lave tube as a result of accumulation, slow movement, and loss of water and massive ice under the effect of gravity; b) Gelifraction, the fracturing of rocks by freezing of water trapped in joints, is an important cause of breakup and collapse inside this ice-rich lava tube
Experimental dataset: stereo-DIC experiment on uniaxially loaded, S-Shaped, high density polyethylene test sample
No full textStereo-DIC experiments were performed on uniaxially loaded, s-shaped, high-density polyethylene test sample. 100 stationary images of unloaded test sample were taken for evaluation of DIC noise floor. Stereo calibration image dataset, involving a calibration target with rectangular grid (12 by 9 and pitch of 10 mm), is also made available. Tensile load from the test bench load-cell sampled at each moment an image is captured is available.</span
Lava Butte wildlife crossing monitoring project
No full textThis archived document is maintained by the Oregon State Library as part of the Oregon Documents Depository Program. It is for informational purposes and may not be suitable for legal purposes.Title from PDF caption (viewed on April 20, 2016)."Prepared on: June 30th 2015, finalized: October 8th, 2015."Evaluates the effectiveness of crossing structures located near Crawford Road Bridges near Lava Lands Visitor Center and South Lava Butte Bridges.Mode of access: Internet from the Oregon Government Publications Collection.Text in English
Pressurized lunar lava tubes for habitation
No full textLava tubes are subterranean tubes that form as a result of lava flows and extend for long distances beneath the surface of a planet. They are a naturally occurring feature of Earth’s Moon. For decades these cave systems have piqued the interest of researchers, not just for their geological complexity, but also for their potential as a future human habitation site on the Moon. The internal environment of lunar lava tubes promises a benign alternative in comparison to the harsh lunar surface; they provide natural protection from radiation, micrometeoroids, and extreme temperature fluctuations. This thesis furthers the study of lunar lava tubes by presenting the possibility of pressurizing them with breathable air. Using a 2D ANSYS simulation model, a range of lava tube sizes are subjected to varied magnitude of internal pressurization. It is ultimately concluded that it is possible to pressurize a small lava tube while maintaining its structural integrity.M.S.Includes bibliographical reference
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