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COSTA JUCA
(XAFUImSTICS OF 'IHE DISASTER
EVENT:
Volcanic EYzlption
DATE~TIME : July 29, 1968 - -sent
LOCATION : Mt. Arenal, Northern Costa Rica
DISASTER VICTIMS: Killed Injured Homeless Evacuated
none
87 seriously 3,280 12,391
PROPERTY DAMAGE:
DESCFUFTION OF THE DISASTER
Homes Destroyed
504 $1,029,193
Eru~tions and Exdosions on Mount Arenal
Mount Arenal volcano ended its many years of quiescence with a violent
eruption at 8 A.M. on Sunday July 29, 1968. Costa Rica has several active
volcanos, one of which, Mt . Irazu, erupted in 1965 and continued spewing
fine ash over Cartago and elsewhere for nearly two years. However, Mt.
Arenal was a "volcano1' only to scientists. There were no historical records
of it erupting and local residents thought of it only as an ordinary morn-.
tain. (Sine the 1968 eruption, scientists have decided, through carbon
dating and potsherds, that it did, In fact, erupt in 1510--just before
the Spanish began keeping records.) The initial explosion on July 209 burst
open a large new crater about halfhay down the west side of the 5,356 foot
muntain. Great quantities of incandescent blocks were hurled up and out
which exploded when they hit the earth leaving "bomb-like" craters. Also
emitted were large clouds of incandescent gases and particles (ndee ardente).
These had an internal temperature in excess of 300°C (lead boils at 327Y).
These burning clouds mved at hurricane speeds over the surface of the
earth instantly Wcinerating everything they touched. For three days the
explosions continued. wee ardente clouds were produced on July 29 and
July 31. All deaths and most devastation occurred between those dates.
This type of eruption is similar to that of Mt. Pel/ee, which exploded on
May 8, 1902, and whose "glowing clouds1' killed the residents of St. Pierre,
Mart inique .
Some ash eruptions rose to an estimated 45,000 feet and small quantities
of light ash reached the Pacific and fell on Nicaragua to the north.
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