Mount Popocatépetl, a 3020 m high stratovolcano (cone-shaped volcano made up of layers of ash and lava) about 70 km from Mexico City in the eastern Trans-Mexican Volcanic Belt, began suffering regular seismic events (small Earthuakes associated with the movement of magma in chambers beneath the volcano) on 14 February 2024, followed by a series of eruptions which produced ash columns up to 6 km high, which drifted to the north, northeast, and south. Ashfalls were reported in the municipalities of Nativitas, Santa Isabel, Tetlatlahuaca, Tlaxcala, Santa Ana Chiautempan, and Zacatelco, and Hermanos Serdán International Airport, was forced to be closed while ash was cleared from its runways. Earthquakes and smaller eruptions persisted for the nest week, with an ashfall again reported in the municipality of Hueyapan on 19 February. A 12 km exclusion zone around the volcano has been declared as a precaution.
Popocatépetl has been more or less constantly erupting since the mid 1990s, but most of the time this activity remains at a low level. Major eruptions on Popocatépetl are a cause for concern as the volcano is in a densely populated area, with 30 million people living within the potential hazard zone. The last major eruption, a Plinian (or Vesuvian) event in about 800 AD, triggered a series of pyroclastic flows and lahars that scoured the basins around the volcano.
The volcanoes of the Trans-Mexican Volcanic Belt are fuelled by the subduction of the Cocos Plate beneath the North American Plate along the Middle American Trench to the south of Mexico. As the subducting plate sinks into the Earth it is melted by the heat and pressure, and volatile minerals liquefy and rise through the overlying North American Plate as magma, fuelling Mexico's volcanoes.
The Cocos Plate is thought to have formed about 23 million years ago, when the Farallon Plate, an ancient tectonic plate underlying the East Pacific, split in two, forming the Cocos Plate to the north and the Nazca Plate to the south. Then, roughly 10 million years ago, the northwesternmost part of the Cocos Plate split of to form the Rivera Plate, south of Beja California.
In a paper published in the Journal of Geophysical Research: Solid Earth, in 2011, a team led by Igor Stubailo of the Department of Earth and Space Sciences at the University of California Los Angeles, published a model of the subduction zone beneath Mexico using data from seismic monitoring stations belonging to the Mesoamerican Seismic Experiment, the Network of Autonomously Recording Seismographs, the USArray, Mapping the Rivera Subduction Zone and the Mexican Servicio Sismologico Nacional.
The seismic monitoring stations were able to monitor not just Earthquakes in Mexico, but also Earthquakes in other parts of the world, monitoring the rate at which compression waves from these quakes moved through the rocks beneath Mexico, and how the structure of the rocks altered the movement of these waves.
Based upon the results from these monitoring stations, Stubailo et al. came to the conclusion that the Cocos Plate was split into two beneath Mexico, and that the two plates are subducting at different angles, one steep and one shallow. Since the rate at which a plate melts reflects its depth within the Earth, the steeper angled plate melts much closer to the subduction zone than the shallower angled plate, splitting the Trans-Mexican Volcanic Belt into sections above the different segments of the Cocos Plate, and causing it to apparently curve away from the subduction zone.
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