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Sand Dunes - Science topic
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Questions related to Sand Dunes
I am facing a problem with some tridimensional dunes and I wanted to ask you a suggestion.
In your opinion, what is the best way to characterize a 3D geometry of dunes. The available data are longitudinal scans at 3 different transversal coordinate and DEM.
I used the zero-crossing method to estimate the characteristi dunes height and wavelength from the bed profile scans. But how can I characterised the trimensionality? I guess from the DEM? how can I characterised the characteristic dune height and wavelength in the transversal direction?
Thanks
Look at Robert Ehrlich's papers and just replace his grain shape parameters with selected dune shape parameters.
One of the methods for combat desertification with the movement of sand dune and dust storms, is to spread pebble and gravel bed.
I want to know how to distribute gravels in wide areas with different percentages. For example, we're going to spread Gravel In a desert area with 100 hectares and with 65% cover. how we can determine the 65% cover. it is easy for test in a wind tunnel because the test trays are small, but this work is very hard and difficult in large desert areas. If anyone has experience about it, I would be grateful if guide me
Although determining the origin of sand storms on the Earth as well as possible, But it is difficult for dust storms. Because this storm covers a large surface area and the specific days, and also dust storms do not always originate from sand dunes.
My laboratory now is conducting research to map an endangered coastal sand dune. I've been looking for how many parameters and what kind of method used to map it? A general workflow perhaps will help me to understand. Thank you.
Is there a new equation to measure sand dune movement?
What is the best technique for measuring sand dune movement in the field?
I placed the word "eggs" in quotation marks, because maybe they are not eggs... These structures shown in the photos were exposed in a sand dune by the wind in the Negev Desert, Southern Israel. They look calcareous with sand attached to them and they are quite hard and elongated. They are thicker than normal hard-shelled reptile eggs (e.g., geckos, turtles etc). They don't look like soft-shelled reptile eggs, that tear and look like an empty paper bag when they dry out (like Varanus eggs). But the most disturbing character is that they are not round in a cross section, as are all reptile (and bird) eggs that I have seen so far. All of them (found on three different occasions) where flattened in the same way and not round in a cross section.
I will be glad to hear from anyone who has seen something similar elsewhere or has an idea for a process that could lead to form these structures (maybe accumulation of calcium on something else, not necessarily an egg?).
Thanks,
Amos
the factors,why its importan and also,how we can protect its ecosystem of coastal sand dunes by its threats
confused to select between Lima - Predictor, CadnaA and sound plan. Needed suggestions particularly for road traffic noise simulation.
Dry season Landsat data constitute my database for the study.
The area is about 20km X 20km.
After a series of enrichment processes for the quartz sand, I arrived at the flotation stage to remove the remaining traces of iron. I am currently looking for a reliable reverse flotation protocol in a flotation cell, I would like to request your precious help in this direction, thank you in advance
Lancaster (1988) suggested the following dune mobility index as follow:
M = W/(P/Ep)
Where W is the percentage of the time that the wind speed is above the threshold necessary for sand transport, P is the mean precipitation, and Ep is the mean potential evapotranspiration. Large M values indicate dune activity. According to Lancaster (1988) dunes are fully activated for M > 200 and most dunes are completely stabilized by vegetation for M < 50. So, I want to know how to Determine the Sensitivity of Climate variability to Sand dune Mobility by Sensitivity Analysis?
In Lancaster equation, I changed the variables of rain, wind and potential evapotranspiration in the range of +-30% and calculate M index. I changed the precipitation, the percentage of wind and evapotranspiration variables to the range of + - 30% and calculated M index in the specified range. Every time I changed one variable the others were fixed. Finally, when I calculated the percentage of the changes with M index and plotted them in Excel, all stations showed the same conditions. Although M index was different at the stations, but the percentages of calculations for each variable were the same at all stations.
Looking for a sample of a concentrate from an ore body with a a silica matrix containing a metal or mixture of metals e.g. Ti, Zr, REEs, even in very small quantities.
Examples include "zircon sand concentrate" ore body concentrate", etc.
Hi. Maybe someone know any publications containing information about the morphological division (sub-unit description) of the coastal foredunes and attached sea beach. I found only coarse units in coastal geomorphology terms like "lee\windward slope", "dune crest", "dune foot", but nothing about more fractional zoning. Blowouts are described as "blowouts" without any sub-uniting. Also with the beach - its possible to find some phrases about "berms", but nothing concrete, with descriptions or definitions of their borders ets.
I have been searching for some articles which may address the problem mentioned above. I could find some excellent papers dealing with origin of red beds in sand dunes but hardly any dealing with fluvial deposits of Holocene or Late Pleistocene.
Any help in this regard is welcomed.
We are interested in comparing patterns of plant species richness and endemism on geologically recent calcareous, coastal dunes in Mediterranean climate regions. Data are readily available for the Mediterranean Basin, the Cape, California, and South-Western Australia, but are sparse and difficult to access for central Chile. A key paper by Alexander Kohler was published in 1970 (citation below), but I have been unable to retrieve a copy thus far. I would greatly appreciate any suggestions of other data sources.
Kohler, A., 1970. Geobotanische Untersuchungen an Küstendünen Chiles zwischen 27 und 42 Grad südliche Breite. Bot. Jahrb. 90: 55-200.
One for geologists. In order to simulate the high temperatures of the mid-K it has been assumed that high CO2 values were involved. New data from pine needles suggests that CO2 ppm levels were close to to modern levels (Barral 2017) so something else had to be responsible. Simulations with higher p atm. can reproduce the mid K wind patterns, temperatures and temperature gradients at about 1.8 atm; this also matches the O2 levels found in amber by Tappert 2013. The only geological evidence of winds is from aeloian sands, which may reflect changes in wind energy and that could suggest changes in density (mass). So the question is two-fold: what should we be looking for ? And is there any suggestion of such a process in the existing data?
(For further details, pls see 'Giant Bugs, etc.' Version 6 on my RG page)
Loss of sand dunes is an important topic of debate as loss of mountains because in desert landscapes sand dunes are important physiographic entity.There loss could have huge environmental impact . Learned members of RG could debate the issue to get clear picture in this context !
I can't seem to find many relevant sources/journals on that topic and I'm wondering if anyone can help me and direct me to an answer or attach any links that are relevant. Thank you.
Please guide!
I am unable to find the standard/recommended values of the following parameters for the coastal sand dunes (after strengthening using bio-cementation or other techniques) so that there can be an upper limit to these values for maintaining a sustainable environment for burrowing animals and plants:
a) Sand’s stiffness (Young’s modulus etc.)
b) Maximum allowable strength (% of cementation) for coastal sand dunes (after strengthening via bio-cementation)
They were found at ancient fire places, where sand dunes have moved away. To me they seem to be neolithic.
Any data available on the thickness of mud layer in the Sunderbans delta?
In application of hard and impermeable polyvinyl compounds for sand dune stabilization there is two opposite concerns for selecting the best stabilizing compound: They are very hard and prevailing compound against wind erosion?, On the other hand, they are impermeable for water and might be sensitive for water erosion and producing runoff? Do you have any idea for making decision which aspect of these compounds is preferred in selection the best compound? Hardness or impermeability?
The best regards and thanks for your responses
In application of hard and impermeable polyvinyl compounds for sand dune stabilization there is two opposite concerns for selecting the best stabilizing compound: They are very hard and prevailing compound against wind erosion?, On the other hand, they are impermeable for water and might be sensitive for water erosion and producing runoff? Do you have any idea for making decision which aspect of these compounds is preferred in selection the best compound? Hardness or impermeability?
The best regards and thanks for your responses
Has anybody faced an issue like that? I have Ca and pH data for an area of decalcified sand dunes. I was quite surprised that massive drop in Calcium levels was not accompanied by the drop in pH. It appears that pH continues to rise in no relation to lime.
The most interesting thing is that it is happening in every habitat type, from foredune to dry heathland area.
I was considering several explanations, and all of them are quite hard to check without further chemical analysis.
From sub-pixel correlation of optical imagery the migration of sand dunes in river bed can be analyzed. How does this analysis enable me to suggest a suitable site for the construction of a bridge?
I'm trying to build a Bayesian model for a coastal dune stratigraphy. The oldest date is taken from marine beach barrier sediments, while the other, more recent, dates are taken from gyttja layers (associated with archaeological remains) embedded within dune sediments
I would like to delineate the patches automatically. The image is of a desert environment with small bush patches on sand dunes. So far I tried "imageSegmenter" in matlab, "image segmentation" and "FLS image segmentation" in ERDAS, and "Segmentation Image" in Envi (which worked best out of all). However, I'm still not completely satisfied with the results I'm getting. Anyone have experience with something similar?
