Dead Sea Receding Shoreline Reveals Amazing Geology

first_img(Visited 202 times, 1 visits today)FacebookTwitterPinterestSave分享0 As the Dead Sea’s water level continues to decline, interesting geology comes to light.The Dead Sea is dying, because the Dead Sea is drying. The well-known body at the lowest elevation on Earth (1,380 feet below sea level) is more than a historical landmark and a geological wonder. It is a place of renowned mineral resources. It is a popular stop on Holy Land tours. Yet its future is very much in doubt, right within our century. Yet the news for science is not all bad.Lena Gregorian wrote a guest entry about the Dead Sea for “State of the Planet,” Columbia University’s Earth Institute blog. Her article begins with a photo of one of the huge sinkholes that have opened up along the receding shoreline. The water level has been receding a meter a year, she says. The recession makes of more of the lake’s mineral wealth, particularly potash used in fertilizers exported around the globe, less accessible to the water-based extraction methods. She urges practices to stabilize the processes in order to preserve the sea for future generations.For a much more in depth article, see the BBC News article by Kevin Connolly. The Dead Sea is a fun place to show off the ability to float while reading a newspaper, as many tourists know. “But the Dead Sea is also a unique ecosystem and a sensitive barometer of the state of the environment in a part of the world where an arid climate and the need to irrigate farms combine to create a permanent shortage of water.” The article includes satellite image comparisons showing the shoreline receding over the past 44 years, mostly due to the taking of water from the Jordan River, its only source. Graffiti of sea level marked during World War I now stands high on a dry rock.The Dead Sea is a land of superlatives that has captivated the ancients as well as modern tourists. “The landscapes of the Dead Sea have an extraordinary, almost lunar quality to them – imagine the Grand Canyon with Lake Como nestling in its depths,” Connolly writes. “And the people of the ancient world understood that there was something unique in the place, even if they couldn’t be quite sure what it was.” It would be a shame for our generation to permanently alter this wonder of the world.The shoreline recession has damaged shoreline industry and tourist operations because of geological activity, particularly sinkholes. There were none 40 years ago. Now, there are 5,500 of them, Connolly writes, showing a photo of a resort severely damaged by sinkholes on the former beach. Sinkhole formation is accelerating. This year, he says, 700 of them formed.They form when underground salt deposits left behind by the sea as it retreats either collapse into huge chasms or dissolve when fresh water seeps underground and causes the ground above to give way.Some of the craters are huge – perhaps 100m across and 50m deep – and in places it looks as though the area is in the grip of a powerful earthquake happening over the course of several decades.Geologists are watching the region with great interest (cf 5/03/04). In the GSA Bulletin, a journal of the Geological Society of America, Israeli and UK geologists were able to study horizontal shear zones from seismic events evident on the Lisan Peninsula because of the receding shoreline. They conclude that significant displacements took place simultaneously during a single earthquake, rather thanDespite the hazard caused by near-surface destructive horizontal displacements during earthquakes, field evidence for coseismic slip along horizontal discontinuities is exceptionally rare, mainly due to the lack of adequate exposure and markers. However, within the seismically active Dead Sea Basin, the late Pleistocene Lisan Formation contains vertical clastic dikes that are sheared laterally at maximum depths of 15 m, and thereby provide unique profiles of such horizontal displacement…. The exceptional quality of exposures and markers enables us to document, for the first time, the details of near-surface horizontal shearing, and indicates that displacement along horizontal bedding planes is a viable mechanism to absorb coseismic deformation in well-bedded near-surface strata.Creation geologist Dr. Steven Austin has also used the opportunity to look for evidence of historical earthquakes (see ICR article). In exposed canyons along Dead Sea shoreline sediments, he believes he has identified several earthquake markers mentioned in the Bible, including the big one recorded by the prophet Amos that shook most of the land of Israel in the time of King Uzziah (Amos 1:1). In another ICR article, Austin describes the extent and consequences of that major quake.The Dead Sea will most likely reach equilibrium with its input sources before drying up completely. Preventing further recession is difficult due to the political differences between Israel, Jordan and other neighbors affected by this large, historic body of water that is 8 to 9 times saltier than the ocean.Much within Israel looks very different today than it did in Biblical times. It’s disconcerting to some tourists to find a shopping mall and hamburger joint on the backside of King Saul’s palace mountain of Gibeah, to say nothing of mosques atop the Temple Mount. But there is still a great deal to see and appreciate in Israel. If you have not toured the Holy Land yet, try to see it while you can. Tensions in the region may continue to escalate to a point that will make travel dangerous. Tourists cannot help but notice who is trying to preserve the history and archaeology, and who is trying to blow it up or rain rockets down onto it.A one-minute video on YouTube draws a spiritual parallel in a “Tale of Two Seas” on the Jordan River: The Sea of Galilee and the Dead Sea. Worth a quick watch.last_img