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Earth of fire

Actualité volcanique, Article de fond sur étude de volcan, tectonique, récits et photos de voyage

Publié le par Bernard Duyck
Publié dans : #Excursions et voyages

The group Klawasi mud volcanoes is located 27 km. east of Glennallen / Alaska, near the western slopes of Mount Drum, a volcano dated of the Pleistocene.

The three mud volcanoes are called Upper Klawasi, Lower Klawasi  and Shrub.

Historically, the first two volcanoes have presented consistently low levels of mud and minor emissions of gases. Shrub was inactive for decades, with only a minor gas discharge in the mid 50. In spring 1997, Shrub began a vigorous eruption of gases rich in CO2 and warm saline mud (McGimsey and Wallace 1999).
 

Upper Klawasi mud volcano -photo McGimsey / AVO

Upper Klawasi mud volcano -photo McGimsey / AVO

Location of the mud volcanoes Klawasi - sources: AVO / USGS - one click to enlargeLocation of the mud volcanoes Klawasi - sources: AVO / USGS - one click to enlarge

Location of the mud volcanoes Klawasi - sources: AVO / USGS - one click to enlarge

Lower Klawasi mud volcano -photo McGimsey / AVO

Lower Klawasi mud volcano -photo McGimsey / AVO

A field visit in June 1999 shows that the discharge from the hot spring remains similar but more widespread than in the previous two years. Animals and plants were found dead in areas near the gas and fluid vents. Maximum temperatures of fluid measured in each main discharge area were equal or superior to those taken during the previous two years, and of the order of 48 to 54 ° C.

The gas emitted by Shrub and Upper Klawasi consist of  98% CO2 and small amounts of nitrogen, argon, oxygen, methane and helium; discharge to the Shrub's vents and sources is estimated at 10 tons / day.


 

Shrub mud volcano, the main pool - photo McGimsey / AVO

Shrub mud volcano, the main pool - photo McGimsey / AVO

The chemical and isotopic analysis of gases and water discharging to Shrub and Upper Klawasi show a combination of mantle (magmatic) and crustal (marine sedimentary rocks) sources, and suggest the presence of a common fluid reservoir in depth.

The cause of changes of discharge and temperature ratio to Shrub need not be bound to an increase of the calorie intake of magma and volatile, but rather to an increase in the permeability of the ascending duct connecting the reservoir to the surface.

 

Sources :

- AVO - Klawasi group - link

- USGS - HYDROTHERMAL ACTIVITY AND CARBON-DIOXIDE DISCHARGE AT SHRUB AND UPPER KLAWASI MUD VOLCANOES, WRANGELL MOUNTAINS, ALASKA By Michael L. Sorey, Cindy Werner, Robert G. McGimsey, and William C. Evans - link

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