Tuesday, June 1, 2010 9:07 PM
Ryan wrote:
“Sinkholes are usually formed by the collapse of a void
underground. Typically this happens in limestone/marble/
carbonate rocks (where caves are normally formed)
because rainwater + CO2 (dissolved in H20) creates a
weak (carbonic) acid that eats at the CaCO3 of the
carbonate rocks (as it seeps down cracks), and begins
creating a gap. As the gap gets larger, more water flows
in, accelerating the process, until, eventually, a cavity
too large to support itself is created an collapses, thus
creating a sink hole.”
After finally finding a geologic map, I found that Guatemala
City is underlain by limestone, which perfectly explains
the sinkhole. Still, this is a classic example of a sinkhole
and the hazards that they pose to people and structures
in urban areas.,
Some of the largest examples of sinkholes are in China
where entire cave systems have collapsed producing
sinkholes that are called “tiankengs”. These sinkholes
are 100s of meters in diameters in diameter and deep.
For example:
Tiankengs in the karst of China by Zhu Xuewen and
Chen Weihai in Speleogenesis and Evolution of Karst
Aquifers at:
http://www.speleogenesis.info/pdf/SG9/SG9_artId3290.pdf
Tiankengs of the world, outside China by Tony Waltham
Speleogenesis and Evolution of Karst Aquifers
http://www.speleogenesis.info/pdf/SG9/SG9_artId3291.pdf
Introduction to Karst Tiankeng in China
http://theculturedtraveler.com/Archives/Nov2005/Karst_Tiankeng.htm
Yours,
Paul H.
