tailieunhanh - ĐỀ THI TIẾNG ANH LỚP 10

TÀI LIỆU THAM KHẢO VÀ TUYỂN TẬP ĐỀ THI TIẾNG ANH LỚP 10 TRƯỜNG THPT Chuyên Bắc Ninh | another form of undersea mountains: the strange guyot, or flat-topped seamount. No marine geologist even suspected the existence of these isolated mountains until they were discovered by geologist Harry H. Hess in 1946. He was serving at the time as naval officer on a ship equipped with a fathometer. Hess named these truncated peaks for the nineteenth-century Swiss-born geologist Arnold Guyot, who had served on the faculty of Princeton University for thirty years. Since then, hundreds of guyots have been discovered in every ocean but the Arctic. Like offshore canyons, guyots present a challenge to oceanographic theory. They are believed to be extinct flat tops indicate that they once stood above or just below the surface, where the action of waves leveled off their peaks. Yet today, by definition, their summits are at least 600 feet below the surface, and some are as deep as 8,200 feet. Most lie between 3,200 feet and 6,500 feet. Their tops are not really flat but slope upward to a low pinnacle at the center. Dredging from the tops of guyots has recovered basalt and coral