Word: sediments
(lookup in dictionary)
(lookup stats)
Dates: all
Sort By: most recent first
(reverse)
Alvarez, his curiosity aroused, shipped samples of the sediment back to the U.S. and showed them to his father Luis, a Nobel-prizewinning physicist also at the University of California, who had the clay analyzed. To everybody's surprise, it turned out to be 30 times as rich in iridium as normal rocks. The Berkeley team knew of only a few places where such high concentrations of the rare element might occur: in the earth's core, perhaps 2,000 miles belowground; in extraterrestrial objects like asteroids (or their fragments, meteors) and comets; or in the cosmic dust drifting...
...chiseled, Alvarez was struck by a configuration of sediment layers, which resembled a sandwich in stone. The bottom or older layer consisted of Cretaceous limestone, which was full of tiny fossils. On top was a second slice of limestone, from the Tertiary period, almost devoid of these fossils. Like other samples of rock from that era, it showed that the creatures alive during the late Cretaceous period had, by geological time scales, suddenly disappeared. In between the limestone layers was a dull red layer of clay about half an inch thick, first discovered by an Italian paleontologist around...
...rapidly accumulating. Other geologists uncovered similar iridium deposits just above Cretaceous rock beneath the floor of the Atlantic Ocean and under the Raton basin in northeastern New Mexico. Additional analysis showed that the samples contained ratios of gold and platinum nearly identical to those found in meteorites. Furthermore, other sediment layers containing abnormally high amounts of iridium were discovered under both the Caribbean Sea and the Gulf of Mexico; these layers were deposited around the time of a smaller mass extinction that occurred more than 30 million years ago, at the end of the Eocene epoch. In addition...
...ship is about 65 ft. long, rigged for a single square sail. Thus far only some of the hull's planking and part of the vessel's keel, made of fir, have been unearthed from the sediment. Apparently, the ship foundered on the coast's treacherous rocks and went straight down, without splintering, thus retaining much of its cargo. Bass and his fellow archaeologists were able to date the ship from at least two clues: a delicate double-handled Greek cup, similar to those made between 1400 and 1350 B.C., and the copper ingots, with their characteristic...
Wyoming has been a favorite haunt of paleontologists for the past century, ever since westering pioneers reported that many vertebrate fossils were almost lying on the ground. Scientists soon discovered why. Roughly 55 million years ago, the Rockies rose violently, while enormous basins formed around Wyoming. Rains washed sediment into the natural bowls, and thousands of animal carcasses were buried and preserved...