We were watching a program on the Grand Canyon. It surprised us with a reference to, and brief description of, the Great Unconformity. We hadn’t heard of it before. There is this possibly related problem of the Cambrian Explosion, a time when complex life seemed to suddenly develop from the simplest organisms like bacteria. Suddenly there were complicated creatures, a sudden explosion of diversity that didn’t exist before. A challenge to our understanding of evolution. In several places on earth where the geologic record is exposed, one being the Grand Canyon, there is a puzzle. There is a billion year gap. The geologic strata are arranged in ages. The newer ages are close to the surface. Penetrate ever deeper and there is a progression back in time. What they realized in the Grand Canyon is that there is a gap in our evidence. There are two layers lying directly in contact with each other that are a billion years apart in their age. We have no record of that billion years between the Pre-Cambrian and the Cambrian period. (It’s greater than a billion years in some places, some places less.) Maybe there was no explosion of life at all. Maybe there was a continuous gradual evolution from the single-celled organisms for a billion years, into the more complex organisms we see today. We don’t know. We have no record of that part. What happened to that billion years of geology all over the planet? Don’t know. Somehow that entire layer got washed away, or otherwise eroded. It’s the Great Unconformity. Is the Great Unconformity related to the Cambrian Explosion? Maybe. Another mystery. Happy Holidays.
Countdown:Birds: 1CPE hours: 3
Countdown:Birds: 1CPE hours: 3 
