巨大沉洞黑洞在危地馬拉城 2010年（危地馬拉特魯比諾金）
西元2010年06月01日
危地馬拉沉洞由人類創造 不是自然界造成
Guatemala Sinkhole Created by Humans, Not Nature
30-story-deep chasm not a true sinkhole, but a "piping feature."
30層樓深的鴻溝不是一個真正的沉洞，卻是一條“特色管道。”
The sinkhole appeared Sunday in downtown Guatemala City, swallowing a three-story building.這沉洞星期日出現在危地馬拉城市中心，吞下一幢三層的建築物。
Ker Than
for National Geographic News
Published June 3, 2010
Human activity, not nature, was the likely cause of the gaping sinkhole that opened up in the streets of Guatemala City on Sunday, a geologist says.
人類活動，不是大自然，是那可能的原因導致上週日危地馬拉城街道打開的沉洞，一地質學家說。
A burst sewer pipe or storm drain probably hollowed out the underground cavity that allowed the chasm to form, according to Sam Bonis, a geologist at Dartmouth College in New Hampshire, who is currently living in Guatemala City (map).
一爆裂的污水管或排水渠可能掏空那地下空洞，讓鴻溝形成，根據美國新罕布什爾州達特茅斯學院地質學家山姆博尼斯，它目前是居住在危地馬拉城（地圖）。
The Guatemala City sinkhole, estimated to be 60 feet (18 meters) wide and 300 feet (100 meters) deep, appears to have been triggered by the deluge from tropical storm Agatha.
But the cavity formed in the first place because the city—and its underground infrastructure—were built in a region where the first few hundred meters of ground are mostly made up of a material called pumice fill, deposited during past volcanic eruptions.
"Lots of times, volcanic pumice originates as a flow [of loose, gravel-like particles], and because of the heat and the weight, it becomes welded into solid rock," Bonis said.
"In Guatemala City [the pumice is] unconsolidated, it's loose," he said. "It hasn't been hardened into a rock yet, so it's easily eroded, especially by swift running water."
In general, the zoning regulations and building codes in Guatemala City are poor, Bonis said, and the few regulations that exist are often ignored. That means leaking pipes could have gone unfixed long enough to create the right conditions for the sinkhole. (Related pictures: "How Humans Can Trigger Earthquakes.")
In fact, Bonis thinks calling the Guatemala City chasm a sinkhole is a misnomer—a true sinkhole is an entirely natural phenomenon. There is no scientific term for what happened in Guatemala, he said, adding that he recommends the pit be dubbed a piping feature.
Guatemala Sinkhole Not a Sinkhole
Natural sinkholes generally form when heavy, water-saturated soil causes the roof of an underground limestone cavity to collapse, or when water widens a natural fracture in limestone bedrock.
But there is no limestone beneath the section of Guatemala City where the new sinkhole appeared, at least not at the depth at which the hole formed, Bonis said.
"There may be limestone thousands of meters beneath the city, but not hundreds of meters," he said.
Instead, nature likely sped up a process set in motion by human actions. (Related: "'Mud Volcano' in Indonesia Caused by Gas Exploration, Study Says.")
Recent eruptions of several volcanoes in Guatemala covered the city in a fresh layer of volcanic ash. If this material got into the city's pipes and drains, it may have clogged the passageways, making ruptures more likely, Bonis said.
Heavy rains from tropical storm Agatha may also have overloaded underground sewage or drainage pipes, leading to a growing cavity that eventually collapsed, Bonis speculated.
The geologist added that the new sinkhole shares remarkable similarities with a sinkhole that formed in Guatemala City in 2007.
"Both of these things occurred in the same general part of town. They look the same," he said. "It's more than a coincidence, especially if they trace" any faulty pipes associated with the 2010 sinkhole to pipes near the 2007 sinkhole.
Guatemala City Sewer Inspections a Must
The danger should not have been news to officials in Guatemala City, noted Bonis, who used to work for the Guatemalan government's national geology institute.
As part of a volunteer team that investigated the 2007 sinkhole, Bonis co-authored a report warning the Guatemalan government that similar holes will very likely keep appearing unless action is taken to inspect the city's sewer system for weaknesses. (Watch video of sewer divers in Mexico City.)
The government never replied, Bonis said—possibly due to a lack of funds.
"There's a minimum of regulation, because that's money that the government doesn't have," he said.
But, he added, "there's got to be ways of inspecting the sewer system. ... These are things that have to be done."
http://news.nationalgeographic.com/news/2010/06/100603-science-guatemala-sinkhole-2010-humans-caused/
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