SANTA MARÍA / SANTIAGUITO VOLCANO Symmetrical, forest-covered Santa María volcano is one of the most prominent of a chain of large STRATOVOLCANOES that rises dramatically above the Pacific coastal plain of Guatemala. Santa Maria erupted catastrophically in 1902 destroying its former summit. Since then, a complex of new lava domes has been growing inside the scar left by the 1902 eruption. The YOUNGEST and STILL ACTIVE DOME is called SANTIAGUITO. Santa Maria is a popular excursion destination and the summit offers spectacular views onto erupting Santiaguito. BACKGROUND: The 3,772 m (12,375 ft) high stratovolcano has a SHARP-TOPPED, CONICAL PROFILE that is cut on the SW flank by a large, 1.5 km WIDE CRATER. The OVAL-SHAPED crater extends from just below the summit of Volcán Santa María to the lower flank and was formed during a catastrophic eruption in 1902. The renowned PLINIAN ERUPTION of 1902 that devastated much of SW Guatemala FOLLOWED a LONG REPOSE PERIOD after construction of the large basaltic-andesite stratovolcano. The massive 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, the most recent of which is Caliente. Dome growth has been accompanied by almost continuous minor explosions, with periodic lava extrusion, larger explosions, pyroclastic flows, and lahars. GEOLOGICAL HISTORY: Santa María Volcano is a large ACTIVE VOLCANO in the Western Highlands of Guatemala, close to the city of Quetzaltenango. Santa María is part of the Sierra Madre range of volcanoes, which extends along the western edge of Guatemala, separated from the Pacific Ocean by a broad plain. The volcanoes are FORMED BY THE SUBDUCTION of the Cocos Plate under the Caribbean Plate, which LED TO THE FORMATION of the Central America Volcanic Arc. Eruptions at Santa María are estimated to have begun about 30,000 years ago. For several thousand years, eruptions seem to have been small and frequent, building up the large cone of the volcano, reaching about 1,400 m (4,600 ft) above the plain on which the nearby city of Quetzaltenango sits. Following the cone-building eruptions, activity seems to have changed to a pattern of long periods of repose followed by the emission of small lava flows from vents on the flanks. The cone built by the eruptions had a volume of about 10 cubic kilometres (2.4 cu mi), and consisted of a mixture of basalt and andesite lavas. [SOURCE: Wikipedia; volcanodiscovery › ... › Guatemala] [PHOTO: 1. Santiaguito from Santamaria; 2. Ash eruption at Santiaguito lava dome (PHOTO: Tom Pfeiffer); 3. The lava dome (PHOTO: Tom Pfeiffer)] [PHOTO Ed.: D. K. Srivastava]
Posted on: Sat, 20 Jul 2013 05:10:21 +0000
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