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Volcano Watch Weekly [6 May 2009]

Posted by feww on May 7, 2009

Volcanic Activity Report: 29 April – 5 May 2009

Source: Global Volcanism program (GVP) – SI/USGS Weekly Volcanic Activity Report

New activity/unrest:

VoW: Atitlán

Country:  Guatemala
Volcano Type:  Stratovolcano
Volcano Status:  Historical
Last Known Eruption: 1853
Summit Elevation: 3,535 m  (11,598 feet)
Latitude: 14.583°N  (14°34’58″N)
Longitude: 91.186°W  (91°11’11″W)


Volcán Atitlán is one of several prominent conical stratovolcanoes in the Guatemalan highlands. Along with its twin volcano Tolimán to the north, it forms a dramatic backdrop to Lake Atitlán, one of the scenic highlights of the country. The 3535-m-high summit of Atitlán directly overlies the inferred margin of the Pleistocene Atitlán III caldera and is the highest of three large post-caldera stratovolcanoes constructed near the southern caldera rim. The volcano consequently post-dates the eruption of the voluminous, roughly 85,000-year-old rhyolitic Los Chocoyos tephra associated with formation of the Atitlán III caldera. The historically active andesitic Volcán Atitlán is younger than Tolimán, although their earlier activity overlapped. In contrast to Tolimán, Atitlán displays a thick pyroclastic cover. The northern side of the volcano is wooded to near the summit, whereas the upper 1000 m of the southern slopes are unvegetated. Predominantly explosive eruptions have been recorded from Volcán Atitlán since the 15th century. Photo by Bill Rose, 1980(Michigan Technological University). Caption GVP.

Major Volcanoes of Guatemala

REPORT:
Volcanic Hazards at Atitlán Volcano, Guatemala

—J.M. Haapala, R. Escobar Wolf, J.W. Vallance, W.I. Rose, J.P. Griswold, S.P. Schilling, J.W. Ewert, and M. Mota, 2006
Volcanic Hazards at Atitlán Volcano, Guatemala U.S. Geological Survey Open-File Report 2005-1403

Introduction

Atitlán Volcano is in the Guatemalan Highlands, along a west-northwest trending chain of volcanoes parallel to the mid-American trench. The volcano perches on the southern rim of the Atitlán caldera, which contains Lake Atitlán. Since the major caldera-forming eruption 85 thousand years ago (ka), three stratovolcanoes—San Pedro, Tolimán, and Atitlán—have formed in and around the caldera. Atitlán is the youngest and most active of the three volcanoes. Atitlán Volcano is a composite volcano, with a steep-sided, symmetrical cone comprising alternating layers of lava flows, volcanic ash, cinders, blocks, and bombs.

Eruptions of Atitlán began more than 10 ka and, since the arrival of the Spanish in the mid-1400’s, eruptions have occurred in six eruptive clusters (1469, 1505, 1579, 1663, 1717, 1826–1856). Owing to its distance from population centers and the limited written record from 200 to 500 years ago, only an incomplete sample of the volcano’s behavior is documented prior to the 1800’s. The geologic record provides a more complete sample of the volcano’s behavior since the 19th century. Geologic and historical data suggest that the intensity and pattern of activity at Atitlán Volcano is similar to that of Fuego Volcano, 44 km to the east, where active eruptions have been observed throughout the historical period.

Because of Atitlán’s moderately explosive nature and frequency of eruptions, there is a need for local and regional hazard planning and mitigation efforts. Tourism has flourished in the area; economic pressure has pushed agricultural activity higher up the slopes of Atitlán and closer to the source of possible future volcanic activity. This report summarizes the hazards posed by Atitlán Volcano in the event of renewed activity but does not imply that an eruption is imminent. However, the recognition of potential activity will facilitate hazard and emergency preparedness. [Report Menu]

Ongoing Activity:

Latest U.S. Volcano Alerts and Updates for Wednesday, May 6, 2009 at 17:51:20 PDT

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