The Formation of Silali Crater (Kenya) As an Extraterrestrial Impact Crater (ETIC)

Abstract

Extraterrestrial impact craters on the earth’s surface are formed by the impact of an asteroid, comet or a meteorite on the Earth’s surface. Silali basin is a depression that is found to the north of Lake Baringo; around Kapedo town. It is suspected to be an Extra –Terrestrial Impact Crater (ETIC). The mechanisms associated with impact craters are diverse but generally, when a sizable solid body strikes the ground at a high speed, shock waves propagate into the target rocks. At collision speeds of tens of kilometers per second, the initial pressure on the material engulfed by the expanding shockwaves is millions of times the earth’s normal atmospheric pressure, which is 10, 300 Newtons per square meter. This can squeeze dense rocks into 1/3 of their normal volume. Stress can then overwhelm target rocks to an extent that they initially begin to flow almost like a fluid. A decompression wave follows the advancing front wave into the compressed rock, allowing the material to move sideways. As more and more of the target rock becomes engulfed in the shock wave, which expands more or less radially from the point of impact, the flow of the target material behind the shock front, is diverted out along the wall of a rapidly expanding cavity created by the decompression wave. The compacted body now vaporized or melted moves outward with the divergent flow and lines the cavity, forming a conical melt sheet. Remote sensing was utilized to map the Silali basin. Satellite images were used to identify the nature of the crater, since most terrestrial impact craters are not identifiable from the surface of the earth. The images provided critical information that was used to map out the morphological aspects of the crater, some of which have long been buried by forces of denudation, together with tectonic and anthropogenic forces. Remote sensing (satellite imagery and ground photography) was supplemented by interviews, observation and sampling of various rock formations.