* Astronomy

Members Login
Post Info TOPIC: Unknown eruption 1808


L

Posts: 131433
Date:
RE: Unknown eruption 1808
Permalink  
 


First eyewitness accounts of mystery volcanic eruption

In February 1809 Caldas wrote about a "mystery" that included a constant, stratospheric "transparent cloud that obstructs the sun's brilliance" over Bogotá, starting on the 11 December 1808 and seen across Colombia. He gave detailed observations, for example that the "natural fiery colour [of the sun] has changed to that of silver, so much so that many have mistaken it for the moon"; and that the weather was unusually cold, the fields covered with ice and the crops damaged by frost.
Read more



__________________


L

Posts: 131433
Date:
Permalink  
 

Title: Observations of a stratospheric aerosol veil from a tropical volcanic eruption in December 1808: is this the "Unknown" ~1809 eruption?
Author: A. Guevara-Murua, C. A. Williams, E. J. Hendy, A. C. Rust, and K. V. Cashman

The "Unknown" eruption of 1808/1809 was the second most explosive SO2-rich volcanic eruption in the last two centuries, only eclipsed by the cataclysmic VEI 7 Tambora eruption in April 1815. However, no eyewitness accounts of the event, and therefore its location, or the atmospheric optical effects associated with its aerosols have been documented from historical records. Here we report on two meteorological observations dating from the end of 1808 that describe phenomena we attribute to volcanic-induced atmospheric effects caused by the Unknown eruption. The observations were made by two highly respected Latin American scientists. The first, Francisco José de Caldas, describes a stratospheric aerosol haze, a "transparent cloud that obstructs the sun's brilliance", that was visible over the city of Bogotá, Colombia, from 11 December 1808 to at least mid-February 1809. The second, made by physician José Hipólito Unanue in Lima, Peru, describes sunset after-glows (akin to well-documented examples known to be caused by stratospheric volcanic aerosols) from mid-December 1808 to February 1809. These two accounts provide direct evidence of a persistent stratospheric aerosol veil that spanned at least 2600 km into both Northern and Southern Hemispheres and establish that the source was a tropical volcano. Moreover, these observations confirm that the Unknown eruption, previously identified and tentatively assigned to February 1809 (±4 months) from analysis of ice core sulphate records, occurred in late November or early December 1808 (4 December 1808 ± 7 days). This date has important implications for the associated hemispheric climate impacts and temporal pattern of aerosol dispersal.

Read more (PDF)



__________________
Page 1 of 1  sorted by
 
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard