Thursday, April 15

The mysterious lines of unknown origin discovered by NASA in Siberia


The mysterious pattern of lines discovered by NASA.

The mysterious pattern of lines discovered by NASA.
EP

Mysterious landforms, for which there is no conclusive explanation, they have been located in Siberia by scientists at NASA’s Earth Observatory.

In the images acquired by the instrument Operational Land Imager (OLI) and Landsat 8, twirling and twirling stripe patterns are seen around an area of ​​hills in the north central Siberian plateau at 66 degrees latitude. On steeper hills, the fringes form narrow loops that spiral from the top of the hill to the bottom. As they descend towards the banks of the river, they begin to fade. Eventually the stripes disappear at lower elevations and latitudes.

There are several possible causes for the distinctive stripe pattern, and answers vary by season and according to the experience of the researcher.

This part of the central Siberian plateau lies within the Arctic Circle, where air temperatures stay below zero for most of the year. Much of the landscape is covered in permafrost that can extend tens to hundreds of meters below the surface. There are different levels of intensity, but this area is generally covered by permafrost for 90 percent of the year.

The land thaws occasionally, and freeze-thaw cycles have been known to create patterns of polygons, circles and stripes on the surface (what is known as “patterned soil”). In the case of the images, the stripes could be elongated circles stretched out on the slopes by such thaw cycles. However, studies have shown that these types of fringes generally occur on a much smaller scale and tend to be oriented downward.

For the geomorphologists, the nature of the soil offers another explanation for the stripes. In such cold regions, soils can become Gelisols, soils with permafrost in their upper two meters and often with darker and lighter layers distinguished by more organic matter or more mineral and sediment content. As the soil freezes and melts, the layers break apart and they are mixed vertically in a process called cryoturbation.

The persistent freeze-thaw action throughout the seasons can cause the layers to line up in a striped pattern. Different types of tundra vegetation (lichens, low shrubs, and moss) they could grow preferentially in these layers of Gelisol, accentuating the stripes that we see from above. But this hypothesis has not been tested on a large scale.

Layer cake geology

From a geologist’s perspective, the different fringes appear similar to layers of sedimentary rocks. Thomas Crafford of the United States Geological Survey called the pattern “geology of the layer cake”, where sedimentary rock layers have been exposed and dissected by erosion.

As the snow melts or the rain descends, chunks of sedimentary rock are dislodged and sent to the ravines below. Such erosion could cause a staggered pattern that appears as streaks from space similar to a slice of layered cake. This pattern is also known as “cliff and bank topography”.

In the winter Landsat image, the snow makes the stripe pattern stands out more than other seasons. The banks would be the lightest stripes (covered in snow) and the cliffs would be the darkest stripes. The digital elevation map of the Arctic The above, based on data from the ArcticDEM Project, provides a clearer perspective of the potential cliff and bank features.

“They look like little cannons, maybe like the Badlands of Dakota del Sur. The horizontal stripes appear to be different layers of sedimentary rock, “said Walt Meier, an ice specialist at the US National Ice and Snow Data Center. “The shape of the erosion pattern looks a little different than standard sedimentary erosion, but I assume it is due to permafrost. Rivers are eroding through frozen ground. There could also be some effect of frost affecting topography.”

Several rivers run through the plateau, including the Markha, and as the stripe pattern approaches the river, begins to fade. This could be the result of sediment accumulation along river banks due to millions of years of erosion.

Louise Farquharson, an arctic geologist at the University of Alaska-Fairbanks, pointed out a region in northern Alaska with a very similar stripe pattern that could be formed by a similar process.

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