暗网禁区

Audio Script

Evidence suggests Yucatan hit by massive tsunami 1500 years ago
March 5, 2015听听听听听听听听听听听听听听听听听听听听听听听听听听听听听听听听听听听听听听听听听听听听听听听 Larry Benson
听听听听听听听听听听听 The eastern coastline of Mexico鈥檚 Yucatan Peninsula, a mecca for tourists at plush resorts like Playa del Carmen and Cancun, may have been walloped by a massive tsunami some 1,500 years ago, according to a new study involving researchers from Mexico and CU-Boulder.
听听听听听听听听听听听 The key evidence for the tsunami is a large, wedge-shaped berm about 15 feet above sea level paved with washing machine-sized stones stretching contiguously for at least 30 miles, says researcher Larry Benson, an adjunct curator of anthropology at CU鈥檚 Museum of Natural History.
CUT 1 鈥淲ell we think it was caused by a tsunami by the force of the wave front -- the surge. It鈥檚 composed of two layers of coarse sand and it has a cover of boulders up to 1 meter in size. (:15) On the rocky headlands, which themselves are about 2 meters high along the coast, the material goes about 150 meters inland from the coast. But along the shallow bays, the material went as far as 400 meters inland.鈥� (:29)
听听听听听听听听听听听 Benson says the berm boulders are composed of coral and fine-grained limestone. He says the force required to rip up this old and new reef material from the seafloor and deposit it above the shoreline had to have been tremendous.听
CUT 2 鈥淚t had probably at least a 6 meter high wave and if this had occurred again, you鈥檇 be up to the second floor of many of the buildings along the coast. (:08) It left deposits at least 400 meters inland but I鈥檓 sure the water went a lot farther because Yucatan at that latitude is basically flat with very little relief.鈥� (:19)
听听听听听听听听听听听 Another indicator that this was probably a massive tsunami and not a hurricane-generated wave is that sections of the same berm can be found along a 150-mile stretch of the peninsula, says Benson.
CUT 3 鈥淎nd it turns out that this berm actually occurs off and on along a 250 kilometer stretch of coast where there are no mangrove swamps so the thing may have affected the entire Yucatan coast.鈥� (:17)
听听听听听听听听听听 Benson says the cause of the tsunami may have been a large earthquake or massive landslide off an island in the Caribbean.
Radiocarbon dates of sediments associated with the extensive berm, indicates the tsunami, which may have consisted of a train of two or even three giant waves 鈥� slammed the coastline in roughly 500 AD.
CUT 4 鈥淭here is a peat deposit that underlies the berm. And that peat deposit extends actually seaward of the present day shore and I sampled it and dated the carbon material and that to get the AD 450 date. (:15) And then we knew that post-classic Mayan ruins were built, some of them were built on top of the berm so we have a sandwich of dates.鈥� (:23)
听听听听听听听听听听听 One implication of the probable prehistoric tsunami is the potential destruction another one in the same region could cause today, says Benson.
CUT 5 鈥淲hen the tsunami hit somewhere between AD 450 and AD 900 plus, there were just a handful of people. And now, like I say, there鈥檚 1.4 million with a lot development for tourism and stuff and it would cause a lot of damage both to property and to lives.鈥� (:17)
听听听听听听听听听听听 Benson and co-researcher Charles Shaw from Centro Ecological Akumal, a nonprofit enviromental and ecological organization in Mexico, published the study online this week in the Journal of Coastal Research.
-CU-
听