Geologic Background:
The symmetrical, forest-covered Santa
María volcano is one of a chain of large
stratovolcanoes that rises above the Pacific coastal
plain of Guatemala. The stratovolcano has a sharp-topped,
conical profile that is cut on the SW flank by a large,
1-km-wide crater, which formed during a catastrophic
eruption in 1902 and extends from just below the summit
to the lower flank. The renowned plinian eruption of 1902
followed a long repose period and devastated much of SW
Guatemala. The large dacitic Santiaguito lava-dome
complex has been growing at the base of the 1902 crater
since 1922. Compound dome growth at Santiaguito has
occurred episodically from four westward-younging vents,
accompanied by almost continuous minor explosions and
periodic lava extrusion, larger explosions, pyroclastic
flows, and lahars.
Historic Activity:
- One of the largest eruption of the 20th century
occurred at Santa Maria in 1902. The eruption left a 700
x 1,000 m crater in the stratovolcano's SW flank and
produced 5.5 cubic kilometers of pumice fragments and
ash. Growth of a dacite dome called Santiaguito began in
this crater in 1922. The largest pyroclastic flow since
1922 took place in 1929 and killed from hundreds to as
many as 5,000 persons.
- During the next three eruptive pulses the active vent
migrated W from a vent called Caliente to vents named La
Mitad (1939-42), El Monje (1949-55), and El Bruje
(1959-63).
Recent Activity:
- Santiaguito dome began 1922 and has been growing
intermittently since. New lobes are added and explosions
and pyroclastic flows occur during periods of dome
collapse.
- Significant dome growth occurred in February
1997.
- Activity continued through 1999 with dome growth and
a thick blocky flow.
- Activity continued in early 2000 with advancement of
flow.
- Flow still active in January 2001.
Data Sources:
- Smithsonian's SEAN Bulletin (V. 1, No. 10 to V. 14,
No. 7)
- Global Volcanism Network (V. 15, No. 1 to V. 26, No.
4).
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