Evidence suggests Yucatan hit by massive tsunami 1500 years ago
March 5, 2015
Larry Benson
The eastern coastline of Mexico’s 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.
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’s Museum of Natural History.
CUT 1 “Well we think it was caused by a tsunami by the force of the wave
front -- the surge. It’s 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.” (:29)
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.
CUT 2 “It had probably at least a 6 meter high wave and if this had occurred
again, you’d 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’m sure the water
went a lot farther because Yucatan at that latitude is basically flat with very
little relief.” (:19)
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 “And 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.” (:17)
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 – slammed the coastline in roughly 500 AD.
CUT 4 “There 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.” (:23)
One implication of the probable prehistoric tsunami is the potential
destruction another one in the same region could cause today, says Benson.
CUT 5 “When the tsunami hit somewhere between AD 450 and AD 900 plus,
there were just a handful of people. And now, like I say, there’s 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.” (:17)
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-