Pre-PopoPopocatépetl volcano seen here from the north is the second highest peak in Mexico. I

Pre-PopoPopocatépetl volcano seen here from the north is the second highest peak in Mexico. It overlooks Mexico City and its eruptions can be seen regularly from the nation’s capitol. The volcano is part of the Trans-Mexican Volcanic Belt, formed from subduction of the Cocos plate beneath Central America. Therefore, volcanism has been present in this area for hundreds of thousands of years, but the current cone of El Popo is much younger. In fact, if you know where to look, there is a fossil remnant of Popocatépetl’s predecessor locked into the current volcanic structure.Stratovolcanoes like Popocatépetl erupt lava that is viscous and contains a lot of water. Sometimes those lavas ooze gently down the slopes creating rugged lava flows; a few of those can be seen in this photo. Sometimes the volatiles rush outwards, fracturing the molten rock and generating ash. However, sometimes the pressure of those gases can be enough to cause a major explosion, one that can literally rip apart an entire volcano.About 14,000 years ago, a major eruption occurred on a peak scientists have named El Ventorrillo – the predecessor to the modern Popocatépetl volcano. That cone was likely similar in shape to the modern volcanic cone, perhaps even larger. During that eruption, something like half of the volcano collapsed and was blasted off to the northwest. During that eruption, ~10 centimeters worth of ash fell in the area of what is today Mexico City. That blast left a collapsed partial cone, basically a ridge with half the volcano missing.The modern day Popocatépetl began growing on this complex, most likely with its main crater centered slightly to the south of the previous crater. On the right hand side of the cone in this frame there are a series of layers and benches that jut out from the cone, disrupting the perfect cone shape. These benches stop about half way up the modern cone. Those layers are remnants of El Ventorrillo; they were all that was left standing after the blast 14000 years ago. The entire surrounding cone has been reconstructed since that catastrophic eruption.Popocatépetl has had several major eruptions since that cone was destroyed, including one in about the year 800 that produced voluminous pyroclastic flows and ash fall throughout the region. Major eruptions like the one that destroyed El Ventorrillo are rare, happening on a volcano like this one perhaps once every few millennia, but the threat of them requires ongoing, careful monitoring of systems like this one.-JBBImage credit: Margarita Olvera Monterd https://flic.kr/p/y8ELaReferences:http://link.springer.com/article/10.1007/s00445-015-0975-2http://link.springer.com/article/10.1007/s00410-014-0966-x -- source link

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