CRATER REFERENCE

CRATER REFERENCE

by: Charles O’Dale

  • IMPACT CRATER/STRUCTURE IDENTIFICATION – Geologic confirmation for an impact event:
    – GEOMORPHOLOGY – One of the first indicators of a possible impact site is “circular geology”.
    – SHATTER CONES/SLICKENSIDES – Shatter cones are distinctive striated conical fractures that are considered unequivocal evidence of impact events.
    – BRECCIA – Breccias are extremely common in the central uplift, in crater-fill deposits, and in the ejecta blanket of meteorite impact craters.
    – FRACTURED ROCK – While travelling toward impact sites I documented fractured rocks increasing in magnitude as we neared the crater site.
    – GRAVITY ANOMALIES – Gravity contours illustrate anomalies caused by fractured country rock under an impact site.
    – MAGNETIC ANOMALIES – Magnetic studies  document the magnetic disturbances within impact structures.
    – SHOCK METAMORPHOSIM – The extreme pressures and temperatures at hypervelocity impacts have caused shock metamorphic effects on target rocks.
    – CRATER EJECTA – When the crater formation process ends, the resulting circular structure and the surrounding area is covered by an ejecta blanket.
    – CRATER RIM – Documentation of surviving crater rims on this planet.
    – CRATER SHAPE – Why are impact craters almost always round? (or polygonal)?
  • CRATER FORMATION – Impact involves the transfer of massive amounts of energy to a relatively small area of the Earth’s surface, in an extremely short period of time (Kinetic energy). Three stages of crater formation:
    – contact & compression;
    – excavation; and
    – modification.
  • CRATER CLASSIFICATION – On this planet, impact craters are divided into – – – three basic morphologic subdivisions:
    – simple craters;
    – complex craters; and
    – peak ring craters.
  • PLANET VS CRATER SIZE – The primary factors governing the size and – – – — – shape of impact craters are:
    – impact energy;
    – gravity; and
    – properties of the target.
  • METEORITE
    – introduction
    – meteorite types;
    – dating meteorites;
    – meteorite glossary; and
    – reference.

Reference:

Osinski G. The Geological Record of Meteorite Impacts Canadian Space Agency 2018