Europe’s punishing late-summer cold front has been busy taking names across the western half of the continent.
The UK has just suffered-through one of it coldest August Bank Holiday weekends ever recorded, the Alps and Pyrenees have recently received heavy summer snow, and now the French are reporting all-time record August lows:
As reported by meteo.bzh, a monthly cold record has just been broken at the Brest-Guipavas airport –located in NW France– where a minimum temperature of 5.8C (42.4F)was registered.
A plunging Arctic air mass was responsible — a phenomenon on the increase due to the historically low solar activity we’re receiving (see meridional jet stream flow). A lack of wind and the absence of cloud cover at night also contributed to the plummeting temps, according to meteo.bzh.
For decades, spelunkers have flocked to the flooded caverns of the Czech Republic’s Hranice Abyss, which stretches farther below ground than any other freshwater cave system. Now, a scientific campaign to the cave has revealed it is 1 kilometer deep, more than twice as deep as previously thought. The researchers also say the abyss formed as groundwater seeped down from the surface, not as water percolated up, as previously believed—a finding that could call into question the origin of other deep caves.
The abyss sits in karst, a Swiss cheese–like terrain formed when soluble rock such as limestone is slowly dissolved by water. Most caves form from the surface downward, when water from rain or melted snow—slightly acidic from dissolved carbon dioxide—makes its way underground, eating into rock and creating cracks that widen over time. However, deep caves can also form from the bottom up, when acidic groundwater heated by Earth’s mantle burbles up. Researchers believed the Hranice Abyss was in this second category because its waters contain carbon and helium isotopes that come from deep inside Earth.
The Hranice Abyss is the world’s deepest freshwater cave. But it is not the deepest overall. That honor belongs to Georgia’s Veryovkina Cave, a 2.2-kilometer-deep incursion formed when sea levels in the neighboring Black Sea dropped dramatically millions of years ago. In 2016, researchers using a remotely operated vehicle estimated the Hranice Abyss to be 473.5 meters deep. However, the vehicle’s fiber optic communication cable kept it from going deeper, and the true extent of the cave system remained a mystery.
In this photo taken Sept. 27, 2016 in the flooded Hranicka Propast, or Hranice Abyss, in the Czech Republic Polish explorer Krzysztof Starnawski, left, and Bartlomiej Grynda, right, are reading images from a remotely-operated underwater robot, or ROV, that went to the record depth of 404 meters ,1,325 feet, revealing the limestone abyss to be the world’s deepest flooded cave, during the ‘Hranicka Propast – step beyond 400m’ expedition led by Starnawski and partly funded by the National Geographic. (AP Photo/ Marcin Jamkowski)
La géologie, une science plus que passionnante … et diverse
