Word: silting
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While the oceans are rising, some coastal land is actually sinking. Much of the East Coast, for example, is made up of silt sediments deposited from rivers, bays and inlets over the past 5,000 to 8,000 years. As the sediments gradually compress under their own weight, the surface sinks lower. On the Gulf Coast, a process called subsidence, caused in part by the extraction of groundwater and petroleum from subterranean layers of sand and clay, has forced the land, already virtually at sea level, to drop 3 ft. a century. In all, the coastline of the northeastern...
Once the trees are gone, denuded slopes are eroded by rainfall, which has been washing soil into 20-sq.-mi. Madden Lake at the rate of half a million tons a year. A study by Hydrologist Luis Alvarado of the Panama Canal Commission shows that silt accumulating at the bottom of the lake has reduced its storage capacity by 5%. By the year 2000 the loss could be as high as 10%, and by 2020 nearly...
...highlight of the mission for Chief Archaeologist Scott Sledge, 38, was the discovery of a brass regimental facing plate, a shieldlike ornament from a soldier's bearskin cap, with the word royal clearly distinguishable. After gingerly brushing away some silt, Sledge recalls, "I came across something shiny right underneath." It was embedded in the surrounding coral, which he had to chip away carefully. Just as he was about to give up for the day and return to the surface, the plate loosened, and he was able to slide it out of the coral in perfect condition. Says Sledge: "That...
...miles, it took Fisher until 1985--and a total of 6,500 magnetometer hits--to identify what he calls the "mother lode," the ; main body of the ship's cargo. Even then, retrieving the treasure was difficult. The deeper waters off the Florida Keys are murky, the bottom heavily silted. Again, technology provided the solution. Several years earlier, Feild had devised a huge pair of fittings that resemble and are called mailboxes, and placed them over the propellers of one of Fisher's tugs, in effect directing the ship's backwash straight down and forming a clear vertical column...
Archaeologists are particularly concerned about the buried remains of wooden hulls, the part of the ship that has sunk into the seabed or been covered by drifting sand or silt and thus preserved. These remnants, which deteriorate rapidly when exposed to the open sea, provide a wealth of information to scientists. Says Richard Steffy, an INA ship reconstructor: "Ships were the most complex structures made by these societies. When you look at the remains of a ship, you're looking at a very high degree of technology within that period." Working with a crew of assistants and archaeologists, Steffy sketches...