Los Humeros volcanLos Humeros volcano is a large caldera system north of the Mexican Volcanic Belt 55 km west-northwest of the city of Xalapa in Veracruz, or 180 km west of Mexico city.
The 21x15 km wide and 400 m deep Los Humeros caldera was the origin of several large explosive eruptions during the past few 100,000 years, and was formed as the result of repeated collapse of the roof above an emptied magma chamber.
Caldera-forming eruptions were dated to about 460,000, 100,000 and 20-40,000 years ago. It still has a very active hydrothermal system and could be considered active with potential for future eruptions.
At present there geothermal activity is exploited at Los Humeros. There are fumaroles and sulfur deposits at the oval-shaped La Calderita crater in the southern part of the caldera.
Introduction:Los Humeros is the easternmost of a series of silicic volcanic centers with active geothermal systems located north of the axis of the Mexican Volcanic Belt, in the area corresponding to the back-arc of the Volcanic Belt.
Eruptive history of Las Humeras
1) Xáltipan Ignimbrite about 460,000 years before present (BP)
The first major silicic eruption produced the 230 cu km Xáltipan Ignimbrite about 460,000 BP. The deposit covered about 3500 sq km and resulted in formation of the 15 x 21 km Los Humeros caldera.
2) Post-caldera lava domes (460,000 - 240,000 BP)
Several lava domes grew within the caldera.
3) Faby Tuff eruption 240,000 BP:
A second plinian eruption occurred about 240,000 years ago and produced the 40 cu km Faby Tuff.
4) Eruption of the Zaragoza Tuff about 100,000 years BP
This eruption was followed by collapse of the the inner 10-km-wide Los Potreros caldera nested within the earlier caldera.
5) Formation of the El Xalapazco caldera about 40,-20,000 BP
A third, much smaller caldera was formed during the last plinian eruption about 40,000-20,000 years ago.
6) Post-caldera lava flows (40,000 until about 20,000 years ago)
Several fissure eruptions occurred after the formation of the El Xalapazco caldera and produced basaltic lava flows, some of which are younger than 20,000 years and have a youthful morphology.
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