This is a fascinating subject, as least to me, as this now is my third blog on the subject.
A first page article in the September 10 issue of The Wall Street Journal stated, "New Clues Emerge of Dinosaurs' Final Day." The huge creatures weren't the only living things being wiped out: three-quarters of all life were killed. The event has been chronicled before; see my earlier blog (April 2019) here:
The Journal article followed a feature story in the April 8, 2019 issue of The New Yorker, which featured the discovery of amazing remnants of the asteroid impact. The site, called the Hell Creek geological formation, is located in what now is parts of North Dakota, South Dakota, Montana and Wyoming. The specific site examined is on private ranch land, a cattle ranch near Bowman, North Dakota It once was a landscape of steamy, subtropical lowlands and floodplains along the shores of an inland sea. As with any lead story in The New Yorker, it's very good and fairly long. This is required reading for anyone interested in this amazing discovery and event.
New forensic techniques have allowed scientists to find a 130 meter deep slice of solidified matter, 1,500 feet beneath the solid sea bed in the Gulf of Mexico in the Chiczulub Crater off what now is the Yucatan Peninsula of Mexico. This is the epicenter of the meteor strike some 65 million years ago; a meteor estimated to be the size of "a city," mentioned in the article as 50 miles in diameter! The impact is estimated to have blasted a hole 100 miles wide and 25-30 miles deep almost immediately. This cataclysm triggered an almost unimaginable series of events: first the mass of sulfur from pulverized rock from the former seabed was ejected into the atmosphere, where it took decades for the mass to cool and eventually fall back to Earth. Over that period, the average temperatures on Earth dropped by as much as 30 degrees Fahrenheit (virtually no sunlight), and the Earth was in a virtual frozen winter over much of its surface. After the instant of impact, scientists estimate that a plume of molten rock splashed into a mountain higher than Mount Everest is today. That "mountain" of molten stuff collapsed into itself and gigantic waves of lava exploded outward and solidified into a ring of peaks. No more than a half-hour later, seawater surged back over the newly formed peaks, covering them with a blanket of impact rocks. Within hours, additional waves choked with shards of volcanic glass and splintered rock deposited much additional material; the peaks were covered with layers of impact rock and additional debris. Scientists have detected traces of organic matter and charcoal in this top layer.
The key discovery of the critical 130 meters (425 feet or so) of the deposits has allowed scientists to construct a nearly by-the-second and then by-the-minute account of the impact as follows:
- Impact to one minute... a 100 KM (60-65 mile) wide crater was blasted out.
- One minute to three minutes ... the crater collapses inward, sending out an immense jet of molten rock upwards.
- Three minutes to sixty minutes ... Waves of sea water surge back and forth to cover the crater and surrounding peaks.
- Within 24 hours ... The backwash adds more and more finely graded debris plus charcoal from distant wildfires formed by the super-heated impact debris.
This sort of catastrophe is estimated to occur rarely (duh!), perhaps once every billion years. However there are several well-known meteors in space, and fairly close to the Earth in planetary terms. Once, called Didymos, is close enough that NASA is planning a mission in 2021 to test ways to safely deflect a dangerous asteroid before it strikes. To make things even more unnerving, an asteroid named Bennu is large enough, at a third of a mile in diameter, to destroy civilization as we know it. This body circles the sun every 1.2 years and ... hold your breath ... will come between the Earth and our moon in the year 2035! This distance has been changing as Bennu's orbit is affected by the rotation of the asteroid and heating from our sun. So far, the shift has been 100,000 miles since the asteroid was charted sixteen years ago, and the distance between the Earth and the moon is only 239,000 miles! See my blog from April, 2016 about Bennu and this risk here:
If all this sounds too far-fetched to worry about, think back to 2013 when a relatively small meteor, about 100 feet in diameter, and weighing "only" 13,000 metric tons, exploded over Siberian Russia with a blast damaging over 7,000 buildings and injuring around 1,400 people. Many people shot videos from cameras in their cars, and you can easily Google shots of the meteor coming in, and the explosion, which fortunately happened in a very rural and sparsely populated area. This would have been catastrophic if it had been over a city.
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