Edmonton Geological Society
A Section of the Geological Association of Canada


Guest Lecture - An Overview of Asteroid Impacts on Earth

  • 27 Jan 2015
  • 12:00 PM - 12:50 PM
  • MacEwan University City Centre Campus - Rm 6-348

An Overview of Asteroid Impacts on Earth

Michael R. Dence, Ottawa ON.  

Tuesday January 27th, 2015

12:00-12:50, room 6-348 City Centre Campus


Abstract - Stimulated by arguments over lunar craters and Meteor Crater, Arizona, and other cryptic structures, meteorite crater research began in Canada in 1950 following the recognition of the New Quebec Crater and the identification of the Brent Crater in Algonquin Park, Ontario.  Topographic and geophysical surveys by the Dominion Observatory were followed by a drilling program 1955-1967.  With the advent of shock metamorphism studies in 1960, concurrent with detailed comparisons with nuclear explosion craters, the positive identification of some 20 Canadian impact structures was possible by 1980, and is now approaching double that number.  The world census is now about 200. Age determinations allow an estimate of average flux over the last 500 Ma of about one impact per million years with kinetic energy of the order of 1020 J or more forming a 20km diameter crater or larger depending on target material properties. The use of computer methods to simulate impacts has dominated research in the last two decades but significant gaps remain between observation and theory.  Some examples will be discussed with particular attention to the shape and depth of the initial excavation (the transient cavity) and the transition from simple bowl shapes to complex craters with different forms of central uplift.
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