Dating terrestrial impact structures
Dating terrestrial impact structures - mormon dating blog
Because the kinetic energy liberated on impact of an object is proportional to the square of its velocity, these high-speed meteoroids can be, gram for gram, more than 100 times as explosive as TNT!
In the case of Meteor Crater, an iron meteorite body only about 30–50 meters in diameter was sufficient to create a crater 1.2 kilometers in diameter.At this time, however, researchers did not yet have a clear understanding of the immense energy that is liberated when an extraterrestrial body hits the surface of the Earth with cosmic velocity.It was only in the 1920s that the first quantitative studies revealed the explosive nature of meteorite impact.This layer is enriched in the siderophile elements (such as iridium), indicating that the clay represents a mixture of normal crustal rocks, which typically have low siderophile-element abundances, and a small percentage of extraterrestrial material.The worldwide integrated volume of the extraterrestrial material in the K-T boundary layer is equivalent to an asteroid approximately 10 kilometers in diameter — large enough to have produced a 200-kilometer-diameter crater.The landscapes of the Moon, Mars, and Mercury have conspicuously preserved this bombardment record because the surfaces of these relatively small planetary bodies have remained unchanged over hundreds of millions of years.
Compared to the Moon, the Earth has been even more heavily bombarded over the course of its history due to its stronger gravitational attraction.Its impact origin was first suspected late in the nineteenth century, when abundant iron meteorite fragments were discovered in the immediate vicinity of the crater.This finding led the mining engineer Daniel Moreau Barringer to embark, between about 19, on a drilling project to find a suspected large iron meteorite body underneath the crater floor.However, impact craters are not immediately obvious on the surface of Earth because our planet is geologically active; the surface is in a constant state of change from erosion, infilling, volcanism, and tectonic activity.These processes have led to the rapid removal or burial of Earth's impact structures.Diagnostic shock effects include shatter cones, multiple sets of microscopic planar deformation features (PDFs) in quartz, feldspar, and most other rock-forming and accessory minerals, diaplectic glass, and high-pressure mineral phases, such as stishovite (a high-pressure form of quartz).