A great geology article at Natural Historian!
MAY 24, 2013
The Chelyabinsk meteor explosion as recorded by a dash-cam of a truck..
Remember the meteor that exploded over Russia earlier this year? A 50 foot diameter object exploded 14 miles above the surface of the earth and created a shock wave that injured 1500 people and damaged more than 7000 buildings. Despite the drama, the lasting effects on the earth were minimal and only small pieces of the meteorite made it to the surface of the earth. Now imagine tens to hundreds of objects up to several thousand feet in diameter impacting the earth’s atmosphere at one time over hundreds of thousands of square miles. That would be catastrophic. Could that happen and what would be the consequences for life on earth? Well, not only could it happen, there is increasing evidence that just such an event did happen in the not so distant past. No, I’m not talking about a giant impact that may have killed the dinosaurs or the crater that sits below the Chesapeake Bay or the one in Arizona. I’m referring to the YDB impact event of course. Never heard of it? Probably not, but the idea has been around for 10 years and has slowly been attracting more interest as the evidence mounts for what may have been the most recent catastrophic event in earth’s history.
What is the Younger Dryas Boundary (YDB)?
The Young Dryas Boudary (YDB) has long been recognized in sediments around the world as marking the beginning of a time in which the world experienced a global decline in temperature for a period of about 1300 years. This period of cooler and dryer weather has been called the Younger Dryas. The boundary that marks the beginning of this period has been dated by various methods, but most prominently C14 radiometric dating, to be right about 12,800 years ago. The YDB also corresponds to the sudden disappearance of many large animals including the American mammoths, mastodons, american camel, dire wolf, native horses (remember all horses in NA today were brought here from the old world) and giant ground sloth in North America, just to name a few. Below are a few examples showing how visible this boundary point can be in the geological record.