http://popsci.typepad.com/popsci/2007/03/a_hole_lot_of_t.html

A father and his two teenage children drowned when this cavernous pit
swallowed up several buildings in the Guatemala City barrio of San
Antonio. The hole, which appeared on February 22, is approximately 100
feet wide and 200 feet deep.

Reeking water, still swirling in the bowels of the hole, offers a
telltale clue to what happened: Sewage flowing from an eight-foot-wide
ruptured sewer main at the bottom of the hole eroded ash and pumice
layers deposited by ancient volcanic eruptions. The leaking liquid
created a shaft that grew upward through the soft ash by a process
called "piping."

Eventually the shaft became so large that it could no longer support the
upper layers of earth, which abruptly collapsed into the empty space.
Recent rains in Guatemala City probably contributed to the collapse by
weakening the surface soil and adding storm-water runoff to the
percolating sewage.
Ric Finch, a retired Tennessee Technical University geology professor
who has done field studies in northern Central America, has not visited
the site but has examined photos of the collapsed shaft. He says the
shaft's walls contain easily eroded volcanic materials, which are found
throughout the valley where Guatemala City is located. The shaft may
have developed very rapidly, Finch says.

Where did the eroded materials go? Mostly likely, they were washed
downstream through the partly blocked sewer main, which is more than
eight feet in diameter. The bodies of the two drowned teenagers were
found in a nearby canyon where the sewer system discharges.

Many news accounts have referred to the collapsed shaft as a "sinkhole,"
but that is not the correct term here. Sinkholes form in places where
the underlying layer consists of limestone or other soluble rock, which
dissolves in water rather than simply washing away like ash. Geologic
maps for Guatemala City indicate that any limestone in the area of the
cave-in would be located well underneath the volcanic deposits.

Limestone-associated sinkholes are common in other regions of Guatemala
(and in Florida). It's uncommon, however, for a sinkhole to be as large
and deep as the Guatemala City pit. Holes in the ground sometimes open
up without warning, but not in this case. Neighbors reportedly heard
noises and felt tremors for weeks before the collapse.

Some 200 residents have been evacuated from the San Antonio
neighborhood, and officials have cordoned off the area around the shaft.
Tom Miller, a geologist at the University of Puerto Rico who has visited
the hole, says that it is slowly enlarging. Officials have used a
remotely controlled camera to examine the damage, and are currently
attempting to re-route the sewage. "The neighborhood does not smell
pleasant," Miller says.-Dawn Stover

March 02, 2007 in The Breakdown

http://popsci.typepad.com/popsci/2007/03/a_hole_lot_of_t.html
A father and his two teenage children drowned when this cavernous pit
swallowed up several buildings in the Guatemala City barrio of San
Antonio. The hole, which appeared on February 22, is approximately 100
feet wide and 200 feet deep.
Reeking water, still swirling in the bowels of the hole, offers a
telltale clue to what happened: Sewage flowing from an eight-foot-wide
ruptured sewer main at the bottom of the hole eroded ash and pumice
layers deposited by ancient volcanic eruptions. The leaking liquid
created a shaft that grew upward through the soft ash by a process
called “piping.”
Eventually the shaft became so large that it could no longer support the
upper layers of earth, which abruptly collapsed into the empty space.
Recent rains in Guatemala City probably contributed to the collapse by
weakening the surface soil and adding storm-water runoff to the
percolating sewage.
Ric Finch, a retired Tennessee Technical University geology professor
who has done field studies in northern Central America, has not visited
the site but has examined photos of the collapsed shaft. He says the
shaft’s walls contain easily eroded volcanic materials, which are found
throughout the valley where Guatemala City is located. The shaft may
have developed very rapidly, Finch says.
Where did the eroded materials go? Mostly likely, they were washed
downstream through the partly blocked sewer main, which is more than
eight feet in diameter. The bodies of the two drowned teenagers were
found in a nearby canyon where the sewer system discharges.
Many news accounts have referred to the collapsed shaft as a “sinkhole,”
but that is not the correct term here. Sinkholes form in places where
the underlying layer consists of limestone or other soluble rock, which
dissolves in water rather than simply washing away like ash. Geologic
maps for Guatemala City indicate that any limestone in the area of the
cave-in would be located well underneath the volcanic deposits.
Limestone-associated sinkholes are common in other regions of Guatemala
(and in Florida). It’s uncommon, however, for a sinkhole to be as large
and deep as the Guatemala City pit. Holes in the ground sometimes open
up without warning, but not in this case. Neighbors reportedly heard
noises and felt tremors for weeks before the collapse.

Some 200 residents have been evacuated from the San Antonio
neighborhood, and officials have cordoned off the area around the shaft.
Tom Miller, a geologist at the University of Puerto Rico who has visited
the hole, says that it is slowly enlarging. Officials have used a
remotely controlled camera to examine the damage, and are currently
attempting to re-route the sewage. “The neighborhood does not smell
pleasant,” Miller says.—Dawn Stover
March 02, 2007 in The Breakdown

http://popsci.typepad.com/popsci/2007/03/a_hole_lot_of_t.html

A father and his two teenage children drowned when this cavernous pit
swallowed up several buildings in the Guatemala City barrio of San
Antonio. The hole, which appeared on February 22, is approximately 100
feet wide and 200 feet deep.

Reeking water, still swirling in the bowels of the hole, offers a
telltale clue to what happened: Sewage flowing from an eight-foot-wide
ruptured sewer main at the bottom of the hole eroded ash and pumice
layers deposited by ancient volcanic eruptions. The leaking liquid
created a shaft that grew upward through the soft ash by a process
called “piping.”

Eventually the shaft became so large that it could no longer support the
upper layers of earth, which abruptly collapsed into the empty space.
Recent rains in Guatemala City probably contributed to the collapse by
weakening the surface soil and adding storm-water runoff to the
percolating sewage.
Ric Finch, a retired Tennessee Technical University geology professor
who has done field studies in northern Central America, has not visited
the site but has examined photos of the collapsed shaft. He says the
shaft’s walls contain easily eroded volcanic materials, which are found
throughout the valley where Guatemala City is located. The shaft may
have developed very rapidly, Finch says.

Where did the eroded materials go? Mostly likely, they were washed
downstream through the partly blocked sewer main, which is more than
eight feet in diameter. The bodies of the two drowned teenagers were
found in a nearby canyon where the sewer system discharges.

Many news accounts have referred to the collapsed shaft as a “sinkhole,”
but that is not the correct term here. Sinkholes form in places where
the underlying layer consists of limestone or other soluble rock, which
dissolves in water rather than simply washing away like ash. Geologic
maps for Guatemala City indicate that any limestone in the area of the
cave-in would be located well underneath the volcanic deposits.

Limestone-associated sinkholes are common in other regions of Guatemala

(and in Florida). It’s uncommon, however, for a sinkhole to be as large
and deep as the Guatemala City pit. Holes in the ground sometimes open
up without warning, but not in this case. Neighbors reportedly heard
noises and felt tremors for weeks before the collapse.

Some 200 residents have been evacuated from the San Antonio
neighborhood, and officials have cordoned off the area around the shaft.
Tom Miller, a geologist at the University of Puerto Rico who has visited
the hole, says that it is slowly enlarging. Officials have used a
remotely controlled camera to examine the damage, and are currently
attempting to re-route the sewage. “The neighborhood does not smell
pleasant,” Miller says.—Dawn Stover

March 02, 2007 in The Breakdown