Long-term evolution of the gas composition of Popocatepetl's plume

Frontiers in Earth Science

Earth and Planetary Science Letters, 2011

Frontiers in Earth Science, 2023

Journal of Petrology, 2005

Frontiers in Earth Science

Chemical Geology, 2001

Soil gas or flux measurements have shown that many active volcanoes release significant volumes of magmatic gas through their flanks. This type of measurement represents a useful and safer method (compared with direct fumarole measurements) for monitoring an active volcano. However, this study shows that not all volcanoes will have a significant diffuse component, even if substantial quantities of gas are released from the crater.The current phase of volcanic activity at Popocatépetl started in December 1994. Since then, frequent ash emissions have been occurring and very large quantities of SO2 and CO2 have been measured in the summit plume: up to 60,000 t day−1 of SO2. From August 1997 until April 1999 over 500 measurements of Rn and CO2 in soil gas were performed, with extensive coverage of the volcano. Surprisingly, no CO2 of magmatic origin has been detected. Levels of up to 14% have been measured in some locations, however, with δ13C values of between −17‰ and −25‰, its origin appears to be biogenic. The average R/Ra value for the He isotopic ratio of samples of soil gas was 0.49 with all samples giving a radiogenic rather than magmatic signature. Some large ravines in the edifice are thought to mark the location of faults. Large displacements have been measured, but only low concentrations of soil gases were recorded. There is no evidence of a geothermal system, which is likely to be connected to the absence of a diffuse gas component.

Archaeological Discovery Journal, 2019

In search of textual references to a monumental lion at Giza predating the Old Kingdom, we focused our investigation on the earliest use of three ancient Egyptian hieroglyphs depicting the frontal and caudal halves of a lion and a fissure-like symbol. These symbols first appear in Egypt's proto-and early dynastic era and form part of Egypt's earliest known set of written language symbols. During the First Dynasty, these symbols were both carved into ivory tags and painted onto jars to designate the quality of oil shipped as grave goods to both royal and private tombs. The same iconography and symbols appear in the creation story recorded on the frieze and upper register of the Edfu Temple's enclosure wall, where the frontal and caudal animal parts are used to name two of seven personified creation words, the so-called ḏ3jsw 1 , uttered during the act of creating the world from the primordial flood Mehit-wrt by Ptah. Here, we show that the appearance of such unusual icons in such different contexts can be explained by a prominent physical feature (a geological fissure) affecting the appearance of the Great Sphinx, thus demonstrating that the original monument including this feature existed before these hieroglyphs were invented. We have previously argued that the Great Sphinx was remodeled from the much older monumental lioness Mehit. Here, we provide further evidence that this monument existed in the form of a lion or lioness at least seven centuries before the time of Khafre (circa 2500 B.C.E.) challenging the conventional model which attributes the original creation of the Great Sphinx to this Old Kingdom ruler.