Few studies have been made on them as such conditions make field surveying extremely difficult. A team of IRD researchers working in partnership with the University of Chile (Santiago) and the Observatoire de Physique du Globe of Clermont-Ferrand (1) focused special attention on the Lastarria-Cordon del Azufre volcanic complex. With a surface area of 1600 km², it is situated in the central Andes Cordillera at the border between Argentina and Chile near Antofagasta.
IRD geophysicists continued such investigations on the deformations at work in the Lastarria-Cordon del Azufre complex in 2003, by using radar interferometry. This measurement method is based on the superimposition of two satellite radar images of the same geographical area taken at different times. The resulting differential signal between the images, termed the interferogram, provides a way of detecting possible deformation of the earth crust. The value of the wavelength associated with it is proportional to the depth of the source of deformation, down in the lithosphere. For this study, the scientists made use of data acquired by ENVISAT, a satellite ESA launched in 2002. Its ASAR (Advanced Synthetic Aperture Radar) sensor enables it, like its predecessors ERS-l, ERS-2, to perform radar imagery in any weathers. This attribute proves particularly useful for surveillance of the mountainous regions of Latin America.Between March 2003 and June 2005, ENVISAT recorded a time-series of eight images of the Lastarria-Cordon del Azufre volcanic complex. The IRD team used special software to process the images and obtained 28 interferograms. This data set led to measurement of inflation of about a centimetre affecting the crust over the whole of the area studied . As in the North American study, a long wavelength regional-scale signal was found, covering a surface area of about 45 km long by 35 km wide corresponding to the entire volcanic complex. A short wavelength signal not previously identified was also revealed, but unlike the first, it was located at the smaller scale of the Lastarria volcano only.
Two distinct hypotheses are envisaged to explain the emission of these two wavelengths. As the inflation measured at regional scale corresponds to a long wavelength signal, it has a fairly deep source, estimated by the geophysicists at between 7 and 15 km down. An inflation located at such a depth is highly likely to be generated by magmatic activity. The source of the short wavelength signal, located at about 1000 m beneath the summit of the Lastarria volcano, is more uncertain, however. Indications nevertheless suggest a link with the circulation of hydrothermal fluids.
Future forecasting of the possible evolution of the Lastarria-Cordon del Azufre volcanic complex requires the acquisition of field data to complement the satellite data obtained. GPS measurements especially will enable researchers to check if these inflation effects measured using satellite data effectively correspond to movements of the earth crust. The hope is to obtain further information on changes of mass or density at depth using gravimetry, a geophysical method used for detecting the spatial and temporal variations of the gravity field. Thus, a modification of gravity combined with a displacement of the terrestrial crust could indicate a filling or an emptying of a magma chamber and therefore confirm an underlying volcanic activity. If this turned out to be true, the Lastatria-Cordon del Azufre volcanic complex would be the only area under the Andes where the formation of large magma reservoirs has been demonstrated. In the future, such observation methods could be applied to studying volcanic activity in many regions, like the Andean Cordillera, where access is difficult and thus make the surveillance of volcanic structures as effective as possible.
Grégory Fléchet | alfa
Arctic melt ponds form when meltwater clogs ice pores
24.01.2017 | University of Utah
New Study Will Help Find the Best Locations for Thermal Power Stations in Iceland
19.01.2017 | University of Gothenburg
A Swedish-German team of researchers has cleared up a key process for the artificial production of silk. With the help of the intense X-rays from DESY's...
For the first time ever, a cloud of ultra-cold atoms has been successfully created in space on board of a sounding rocket. The MAIUS mission demonstrates that quantum optical sensors can be operated even in harsh environments like space – a prerequi-site for finding answers to the most challenging questions of fundamental physics and an important innovation driver for everyday applications.
According to Albert Einstein's Equivalence Principle, all bodies are accelerated at the same rate by the Earth's gravity, regardless of their properties. This...
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
24.01.2017 | Physics and Astronomy
24.01.2017 | Life Sciences
24.01.2017 | Health and Medicine