BackgroundCofre de Perote is a massive Quaternary andesitic-dacitic shield volcano that anchors the NNE end of a volcanic chain extending southward to Pico de Orizaba (Citlaltépetl) volcano. The earliest activiy from Cofre de Perote started about 1.6 million years ago.
Lava flows dominated in formation of the broad shield volcano, which is largely of Pleistocene age and is morphologically distinct from the steep-sided stratovolcanoes of the Mexican Volcanic Belt. Glaciation at the summit has left a steep-sided, box-like peak, which is sometimes referred to as the "Treasure Chest of Perote."
A large compound escarpment formed in part by multiple edifice collapses cuts the eastern side of the volcano. Numerous cinder cones dot the flanks of Cofre de Perote. A cluster of very youthful basaltic cinder cones is located on the NE flank, and young lava flows have traveled eastward to beyond the major city of Jalapa (Xalapa), the capital of the state of Veracruz.
(Smithsonian / GVP)
Multiple catastrophic edifice-collapse events
The summit of Cofre de Perote is cut by a series of scarps open to the SE which were formed by large-scale flank collapse events. At least 2 large corresponding debris avalanche deposits were identified, the Xico avalanche and the Los Pescados debris avalanche deposit. The events producing these avalanches were not necessarily related to eruptions, but rather gravitational instability.
Similar deposits are known from nearby Pico de Orizaba and Las Cumbres volcanoes. Some of the resulting avalanches and transformed flows had exceptionally long runouts and reached the Gulf of Mexico.
Los Pescados avalanche
This deposit formed less than 26,000 years ago and forms the lowermost channel-filling terrace deposit of Los Pescados River and extends more than 50 km. It lacks hummocks and more resembles a lahar, with large boulders and coarse gravels, but it is believed to be the result of catastrophic flank collapse.
The Xico avalanche deposit was dated to be only about 10,000 years old. It extends at least 20 km from the summit and is mostly found along river valleys. According to Carrasco-Núñez et al (2006), it is apparently unrelated to any volcanic activity of the volcano, and "other triggers such as earthquake shaking or unusual heavy rainfall must be considered as the initiating cause."
Source and further reading:
- G. Carrasco-Núñez et al. (2006) "Multiple edifice-collapse events in the Eastern Mexican Volcanic Belt: The role of sloping substrate and implications for hazard assessment", Journal of Volcanology and Geothermal Research, v 158, pp. 151–176
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