Where Are the Earth's Impact Craters?
The number of impact craters on Earth is almost negligible compared to Mars and the moon. Can erosion explain this?
Scientists have estimated that there must be about 340 undiscovered meteor craters on the Earth, Science Daily reports. Only 188 have been observed so far.
Meteorite impacts have shaped the development of the Earth and life repeatedly in the past. The extinction of the dinosaurs, for instance, is thought to have been brought on by a mega-collision at the end of the Cretaceous period. But how many traces of large and small impacts have survived the test of time? In comparison to the more than 300,000 impact craters on Mars, the mere 188 confirmed craters on Earth seem almost negligible. Moreover, 60 of them are buried under sediments. Advances in remote sensing have not led to the expected boom in crater discoveries: An average of only one to two meteorite craters are discovered per year, most of them already heavily eroded.
The moon, we know, is heavily cratered. The explanation usually given is that plate tectonics and erosion on Earth erase our craters. Still, the low number is surprising—and sobering:
“A surprising, initially sobering finding we made was that there are not many craters of above six kilometers in diameter left to discover on the Earth’s surface,” reports [Stefan] Hergarten [U of Freiberg]. In the case of smaller craters, on the other hand, the scientists found the current list to be far from complete: Around 90 craters with a diameter of one to six kilometers and a further 250 with a diameter of 250 to 1000 meters are still awaiting discovery. While there are undoubtedly still a number undiscovered large craters buried deep under sediments, they are much more difficult to detect and confirm.
It would seem that craters could be detected indirectly with seismic studies, shocked minerals, or meteoritic material in sediment facies. The short article was not specific in the methods used.
Why was this “surprising” and “sobering”? The difference of three orders of magnitude in crater counts between Mars and the Earth begs for explanation. Surely erosion is a big factor, but why do we not find more evidences of meteoritic material and impacts in large exposures, such as the Colorado Plateau? Upheaval Dome in Canyonlands is notable as an exception to the rule; for hundreds of square miles, strata are perfectly flat, as seen in Grand Canyon. Is it reasonable to assume hundreds of millions of years passed with so few traces of impacts? The conformable strata argue, instead, for rapid deposition of the layers without the passage of deep time. It would seem that Earth, in a much larger gravitational well than the moon and Mars, should have many, many more surviving astroblemes (impact scars) that are found, if hundreds of millions of years have passed. This is a topic creation geologists should take the lead on. Dr. Steven Austin, formerly with ICR, has lectured on this subject. Dr. Walt Brown has also created a model for meteors and the Flood.
Now that scientists have realized that crater count dating is flawed (5/22/12), and may not have anything to do with time (search this site for “crater counts”), it would be good to see more work on the implications of crater data on the age of the Earth. Creation geologists will need to consider the “impact” of giant impacts (6 km craters) on the ecology. Is it possible the Creator has protected the planet (except possibly during the Flood year) that He designed for life from the devastation of impacts that have so scarred the lifeless planets and moons of the solar system? Given all the other factors that have converged on Earth to make life possible, the hypothesis of divine protection should not be dismissed. In the book of Revelation, John foresaw a “mountain burning with fire” impacting the land, and another the sea, leading to widespread death. These, however, are in times of judgment in the last days. It’s interesting that he saw a third of the creatures dying from these impacts, long before any physicists could have calculated the effects on the ecology from large meteors.
July 14th is Pluto Flyby day! Be sure to watch the news of this historic encounter.