ENVIRONMENTAL PERTURBATIONS CAUSED BY THE SERRA DA CANGALHA IMPACT CRATER STRUCTURE, NORTHEASTERN BRAZIL
*Adepelumi. A. Adekunle Sergio. L. Fontes, and Jean. M. Flexor
Departamento de Geofísica, Observatório Nacional, Rua Jose Cristino 77, CEP 20921-400, São Cristóvão, Rio de Janeiro, Brasil. email: adepelumi@yahoo.co.uk
Accepted in January 2004.
Abstract
This paper includes a discussion on the effects a meteorite impact had on the Serra da Cangalha region in northeastern Brazil and the resultant environmental perturbations that occurred in the region. These environmental perturbations were large enough to seriously affect the earth’s global environment after the impact. The effects of such an impact on both the land and the atmosphere constitute the focus of this paper. Such effects include ejecta dispersal, shock wave, landslides, global wildfires, clouds of dust, and overall atmospheric cooling. The result of these effects had in the past been and would in the future be the devastation of many of the organisms living at the time of the impact. Such a major and sudden change in the conditions of the planet would result in a huge depletion of biomass. Using the Pi-scaling relations, we deduced that the impactor propably came from a northwest-to-southeast trajectory at a low angle of 25o to 30o. The geodynamic interpretation indicates that an impact energy equivalent to about 1.8 x 104 Megatons of TNT was released during impact. This energy is well below the stipulated nominal threshold for global disaster (3 x 105 Megatons of TNT), but is within the range described as subglobal disasters. A ground impact of the projectile would have set up an atmospheric blast wave that delivered key peak pressure at a maximum radius of 156 km. This could have resulted in an earthquake surface-wave magnitude (Ms) of 9.2, a rough proxy for Richter magnitude leading to a substantial damage in the region. Also, a peak shock pressure of about 47 GPa was generated during the impact. This peak shock pressure is well below the levels necessary for generating melts which explains the low melt volume found. Based on our research findings, we deduce that the impacts from earth-crossing objects (asteroids and comets) that struck the Serra da Cangalha region about 300 million years ago is enough to have devasted the local ecosystem and biota leading to a high mortality rate at that time.