Comparison of Bosumtwi Impact Crater (Ghana) and Crater Lake Volcanic Caldera (Oregon, USA): Implications for Biotic Recovery after Catastrophic Events

Abstract

Impact craters and volcanic collapse calderas involve catastrophic processes that cause destruction of plant and animal communities in the surrounding areas, leading to new habitats that are initially barren. These events are followed by variable periods of recovery of the biota. Impact craters and calderas are rather similar in form, structure and internal geometry. Furthermore, they are commonly sites of crater lakes. In order to shed light on the processes involved in the destruction and the phases of recovery of biota after a catastrophic impact, we compared the similar-sized (similar to 10 km diameter) Crater Lake (Oregon) caldera and the Bosumwi (Ghana) impact crater lake. Crater Lake was produced by a major caldera-forming explosive eruption 6,845 50 radiocarbon years BP. A lake was established within about 150 years after the caldera collapse, during an early stage of hydrothermal activity. Palynological studies of lake sediments show that forests had become reestablished on the higher ground around Crater Lake by about 300 years after the eruption. Bosumtwi Crater was formed by the impact of an object roughly 0.5 km in diameter that instantaneously released about 4 x 10(19) J of energy. Impact-induced hydrothermal systems may have been active for thousands of years. Volcanic hydrothermal systems may be much longer lasting, and recurrent volcanic activity may continue to disturb the environment around calderas for extended periods of time. These factors could have led to different re-colonization patterns at impact craters and volcanic calderas.