Las Cumbres is a

stratovolcano A stratovolcano, also known as a composite volcano, is a typically conical volcano built up by many alternating layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with ...

Puebla Puebla, officially the Free and Sovereign State of Puebla, is one of the 31 states that, along with Mexico City, comprise the Federal Entities of Mexico. It is divided into 217 municipalities and its capital is Puebla City. Part of east-centr ...

, Mexico. It features an amphitheater-shaped

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...

measuring across with its eastern wall breached. Major lava flows around the volcano are andesitic. Inside the crater is a

dacitic Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. ...

lava dome In volcanology, a lava dome is a circular, mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions ...

. Previously thought to be as tall as

Pico de Orizaba Citlaltépetl (from Nahuan languages, Náhuatl = star, and = mountain), otherwise known as Pico de Orizaba, is an active volcano, the highest mountain in Mexico and Table of the highest major summits of North America, third highest in North Ame ...

, the cone was destroyed in an ancient debris avalanche.

Volcanism

Much of Las Cumbres formed during the early to middle

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

, and volcanism ended by the late Pleistocene. At the time, the volcanic cone was glaciated, similar to all volcanoes taller than . Prior to a major cone collapse, Las Cumbres may have been approximately the same height as Pico de Orizaba (). The catastrophic eruption has been dated to approximately 16,980 ± 870 years

Before Present Before Present (BP) or "years before present (YBP)" is a time scale used mainly in archaeology, geology, and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Because ...

, beginning with

phreatomagmatic Phreatomagmatic eruptions are volcanic eruptions resulting from interaction between magma and water. They differ from exclusively magmatic eruptions and phreatic eruptions. Unlike phreatic eruptions, the products of phreatomagmatic eruptions conta ...

explosions as magma interacted with the glaciers. This also generated significant lahars. The eruption transitioned to a

plinian Plinian eruptions or Vesuvian eruptions are volcanic eruptions characterized by their similarity to the eruption of Mount Vesuvius in 79 AD, which destroyed the ancient Roman cities of Herculaneum and Pompeii. The eruption was described in a le ...

phase when external water could not make contact with magma. The volcano erupting about of magma in this stage which triggered the cone's collapse. The collapse was directed to the east, depositing an estimated of the cone towards the present-day Huitzilapan and Pescados rivers. Field survey indicated the deposit covered . Close to the volcano, these deposits were up to thick and clastic rocks were the size of

boulder In geology, a boulder (or rarely bowlder) is a rock fragment with size greater than in diameter. Smaller pieces are called cobbles and pebbles. While a boulder may be small enough to move or roll manually, others are extremely massive. In ...

s. Some away, the collapse avalanche transitioned into a

debris flow Debris flows are geological phenomena in which water-laden masses of soil and fragmented Rock (geology), rock flow down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors. ...

. Near the Gulf of Mexico, some away, the flow became hyperconcentrated. Following the collapse, the eruption entered its vulcanian phase when water was able to interact with magma. This caused phreatomagmatic eruptions to resume, and another plinian eruptive phase occurred when the unobstructed volcanic vent allowed magma to flow. The horseshoe-shaped caldera and collapse deposit was partly buried by a lava flow. The dacitic lava dome marked the end stage of the eruption phase.

References

{{reflist Volcanoes of Puebla Vulcanian eruptions Plinian eruptions Phreatomagmatic eruptions Sector collapses Stratovolcanoes of Mexico North American 3000 m summits

Volcanism

See also

References