Tales from the Island of Serendip 4 4

[Flex Mentallo]

 

 

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[MrBedrock]

I heard a really cool program on NPR about the extinction event that brought about the end of the dinosaurs. When I was a kid we were taught that after a large object crashed into Earth the resulting cloud of debris cooled Earth's atmosphere for many years and the Dinosaurs gradually died off. Now scientists are proposing that the asteroid actually liquefied the material it displaced on impact. This material turned to steam and ejected into the atmosphere where it began cooling and turning into glass. The glass rained back down and heated the entire atmosphere covering the Earth to temperatures above 750 degrees. Everything exposed was cooked. The total time for worldwide extinction is now guessed to be a matter of hours.

 

Another interesting thing is that they are pretty sure the impact happened in May or June based on the presence of specific pollen in the impact rock and the time of year those plants pollinate.

[Flex Mentallo]

That's fascinating. I had not heard of that variation on the theory! I'm glad you posted it, because I was later going to cover Extinction events.

 

 

 

[Flex Mentallo]

This was the latest of five great mass extinctions, and at least 20 lesser extinctions. The dinosaurs got their chance because of a previous extinction, in fact. And of course, because they died out, around 60 million years ago, birds which descended from theropod dinosaurs and the mammals inherited the planet. Otherwise we'd still be voles!

 

For a time, birds ruled the Earth. The link to dinosaurs is readily apparent - they are aptly named 'terror birds'.

 

 

 

 

[Flex Mentallo]

The largest extinction took place about 250 million years ago. It is known as "The Great Dying", and all life could easily have been extinguished. An estimated 96% of all species were wiped out in massive volcanic upheavals. Lava covered entire continents.

 

Ironically, the dominant reptiles of that day had more in common with mammals than dinosaurs. Easy to confuse Inostrancevia here with a sabre tooth cat!

 

 

 

[Flex Mentallo]

The fossils of the Burgess Shale, like the Burgess Shale itself, formed around 505 million years ago in the Mid Cambrian period.

 

 

 

 

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They were discovered in Canada in 1886, and Charles Doolittle Walcott collected over 60,000 specimens in a series of field trips up from 1909 to 1924.

 

 

 

 

[Flex Mentallo]

The shale, actually fine sediment laid down in shallow seas, uniquely captured the forms of delicate non-vertebrate creatures.

 

 

 

 

[Flex Mentallo]

The so-called 'Cambrian explosion' is a time when life was suddenly seen in great abundance and variety that approaches the current population of earth. Before this, life seems to have been relatively scarce. These Cambrian creatures were extraordinary.

 

 

 

 

[Flex Mentallo]

Hallucigenia is aptly named.

 

 

 

 

 

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When most were wiped out in a series of extinctions, it was relatively scarce vertebrate creatures that survived.

 

 

 

 

[Flex Mentallo]

Myllokunmingia, recently discovered in China, may be the granddaddy of all fishes - and therefore, of us.

 

 

[Silver Surfer]

I heard a really cool program on NPR about the extinction event that brought about the end of the dinosaurs. When I was a kid we were taught that after a large object crashed into Earth the resulting cloud of debris cooled Earth's atmosphere for many years and the Dinosaurs gradually died off. Now scientists are proposing that the asteroid actually liquefied the material it displaced on impact. This material turned to steam and ejected into the atmosphere where it began cooling and turning into glass. The glass rained back down and heated the entire atmosphere covering the Earth to temperatures above 750 degrees. Everything exposed was cooked. The total time for worldwide extinction is now guessed to be a matter of hours.

 

Another interesting thing is that they are pretty sure the impact happened in May or June based on the presence of specific pollen in the impact rock and the time of year those plants pollinate.

 

Fascinating stuff. Imagine the polar ice caps melting as a result and then possibly evaporating?