CANNON, P. JAN
Planetary Data, Tecumseh, OK
Abstract: The Morphology and Structure of Buried Impact Craters
The most common and oldest planetary landform in the universe is an impact crater. The craters are created by the energy expended when a piece of space debris (meteor, meteoroid, or asteroid) enters the gravitational attraction (also referred to as the gravity well) of a planet and subsequently collides with the planetary surface. The mass of the projectile coupled with its hypervelocity creates a crater and completely disintegrates the meteoroid.
On any planet, as impact craters increase in size, there are morphological changes that occur as certain thresholds of energy are crossed. Small craters are simple bowl shapes. On Earth, when the energy levels are great enough to excavate a hole more than 5 kilometers in diameter, an uplifted complex of fractured bedrock begins to form in the geometric center of the crater. This is due to the backwards reflection of the original shock wave that is generated at the time of impact. The effects of fracturing may be seen in the rock beneath the central uplift to depths that are equal to the radius of the crater. Rock materials may be physically brought up from depths that are equal to the crater's original depth. When terrestrial craters are blasted to diameters of about 15 kilometers or larger, the central uplift takes the form of a rough ring of hills surrounding a dome shaped depression floored with breccia. At this point the craters are often referred to as multi-ring basins.
The optimum locations for preserving an impact crater are the near-shore areas of basins that continued to receive sediments after impact or were quickly transgressed by a rising sea
AAPG Search and Discovery Article #90918©1999 AAPG Southwest Section Meeting, Abilene, Texas