“It was thought that the sinking had ... stabilized, but now
we know it will continue into the future indefinitely.” — YEHUDA BOCK
By Devin Powell
Venice is still sinking and will probably
continue to do so for a long time, a new
study suggests. That’s bad news for the
local government, which had already
put a stop to groundwater pumping in
an effort to curb the city’s subsidence.
“It was thought that the sinking
had pretty much been stabilized, but
now we know it will continue into the
future indefinitely,” says Yehuda Bock,
a geodesist at the Scripps Institution of
Oceanography in La Jolla, Calif.
Today’s sinking has little to do with
human activities, Bock and colleagues
report online March 28 in Geochemistry,
Geophysics, Geosystems. Soil is compacting
beneath Venice, bringing the city down.
It rides atop a slab of Earth’s crust that
is slowly diving beneath the Apennine
Mountains, giving the city a tilt noticed
for the first time in the new study.
Data collected by GPS devices and
satellite radar systems showed the city
dropping an average of 1 to 2 millimeters
per year from 2000 to 2010.
Data from satellite
radar systems and
GPS devices reveal
that Venice (
section shown) sank at
an average rate of
1 to 2 millimeters
per year from 2000
to 2010, with some
areas (red) subsiding even faster.
That’s slower than it sank decades ago,
says Bock, and slower than other cities
such as New Orleans are sinking today.
So some researchers don’t think this natural subsidence is worth worrying about.
“We think this is a very small number,” says Tazio Strozzi, a physicist with
the remote-sensing company GAMMA
in Gümligen, Switzerland. Previous satellite measurements have detected a similar
amount of subsidence, he says.
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May 5, 2012 | SCIENCE NEWS | 15