In a sandfall, dry sand either falls vertically over suitable drops or cascades down hard slopes, creating stunning visual effects. The process has been described as “dry sandflows cascading down the escarpment face, where the grain concentration decreases dramatically and the streaming component of stress greatly exceeds the collisional component”

Sometimes water enters the mix and makes sand rivers possible too. When it rains in the desert and the water isn’t absorbed quickly, liquid can mix with the top layer of sand … and this wet sand can form moving rivers and waterfalls that you have to see to believe.

Sand generally can’t flow on its own like water as it quickly reaches a stable point where all the sides are at the angle of repose. If you have a very steep bank or sand dune then sand can flow down the side (which can actually be pretty dangerous if you are under it) but it self-limits and stops relatively quickly.

The post Sandfalls: Amazing Lakes, Rivers & Cliffs of Moving Sand first appeared on Gajitz.

A new solar-powered machine developed by Belgian scientists turns urine into beer, but could also be used to recycle waste into fresh water in areas of need.

Ghent University researchers created this system with developing nations in mind, particularly: sunny locations with plenty of solar access but limited fresh water and located off the grid.

Urine is collected in a tank, heated and cleaned, filtering out nutrients to be used as fertilizer – a ‘whole buffalo’ approach that reuses each aspect of what would ordinarily get flushed and forgotten.

At a public event, the group debuted the system and gathered 1,000 liters pee from festival attendees. Naturally, they then brewed the resulting contributions for redistribution as beer.

Dr Sebastiaan Derese, who worked on the device, said: “We’re able to recover fertilizer and drinking water from urine using just a simple process and solar energy.”

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Thai fireflies gather annually to glow, flashing in great quantities in the country’s mangrove forests. Artists Robin Meier and André Gwerder stepped into the mix, adding artificial flashers to sync up the natural bioluminscent species.

Some types of firefly will synchronize on their own, but following their natural rhythms. By introducing fakes into the mix, the pair of artists tricked a huge group into following their cues, pulsing in controlled patterns and sequential clusters.

“Synchronicity (Thailand) is a video documentation of an experiment where live fireflies are made synchronise their flashes to computer controlled LED’s. Throughout the video the artists explore the relationship between mathematical models of this complex group behaviour and their biological reality in the field. By influencing living fireflies with computer controlled lights they question the idea of free will and simultaneously transform a machine into a living actor inside a colony of insects.”

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A recent sinkhole that suddenly appeared in the backyard of a home in Cornwall is a worrying indicator of hidden risks below seemingly ordinary streets and yards. This particular shaft, which drops 300 feet to the water (and possibly hundreds more below the waterline) looks man-made for a reason: it is really a remnant of the regional tin mining industry, simply covered, boarded up and built over when they were finished with it.

But this is just the tip of a mostly-hidden iceberg, per Subterranea: “As mines close, companies put very large blocks of timber, often old railway sleepers, across shafts and backfilled them, thinking this would be safe. Gradually all evidence of the engine houses and covered shafts disappeared from view and memory and in the past builders assumed there was nothing there. Had they consulted old maps they would have known about the shaft. The timbers rotted over the years and collapses like this often happen after long periods of rain, which they have had in this area.”

Sand, salt and chalk mines across Britain and around the world pose underground risks to everyday city dwellers, who assume their homes are built on solid foundations. Poor record keeping and time conspire to make these threats all the more impossible to anticipate without using ground-penetrating radar and other technologies in advance. Often, things remain stable for years, decades or even centuries, then give way during severe rains or floods. When buying a home in an area with a history of mining, be sure to check it out as best you can in advance.

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A student from Quebec, Canada, has stumbled on the find of a lifetime at the shockingly young age of 15: a long-missing Mayan city, tracked down using star maps. William Gadoury was following a theory that star-obsessed Mayans built towns in layouts that aligned with their constellations, arranging cities below along the same lines as stars above. Looking at star maps, he found a set of three cities where one, he theorized, was missing (two parts of a three-star constellation). He began exploring satellite images of the area in the Yucatan jungle, coming eventually across what appear to be large man-made shapes visible under the forest cover.

Canadian Space Agency scientist Daniel De Lisle, who has worked with satellite images for over 20 years, said the city was likely lost because the jungle is dense in that location. De Lisle said, “There are linear features that would suggest there is something underneath that big canopy. There are enough items to suggest it could be a man-made structure.” Geography professor Dr. Armand La Rocque agreed, with the assessment, suggesting the unnatural square shape may be the base of a pyramid, and pointing out adjacent lines that seem to show a street network.

Gadoury, as its discoverer, is calling the city K’aak Chi, which translates to Mouth of Fire. A scientific journey will publish his findings. Sooner or later, it is expected that archaeologists will travel to the location he identified to see what the shapes are up close, and perhaps discover a few more answers about the mysterious ancient civilization and how they positioned their cities.

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