#k-t extinction

[bleachedbonesdinostore]

Our Ancestors Survived ☄

[peachdoxie]

It's super wack to think that the original paper theorizing that dinosaurs were killed by an asteroid is less than 50 years old. Like I grew up being taught that an asteroid caused the K-T extinction event, but there are many people alive today who weren't because it wasn't even proven yet.

[justgoji]

“Tomorrow is a hope, not a promise.”

[vensosaurus]

[ravageknight-eternal]

Extinction

A memory that wakes me in the night.

Panic and fear.

A midnight dark throbbing; lanced through its dark heart with shimmering pulsing silver-violet rays.

Clouds lit up from above and shivering—shunted aside by unseen butchering.

Singular silent star kissing dark horizon: bathing all in eerie brightness, mushrooming up and outward.

Then, silence. A silent world entombed—

Loudness. Final draconian breath so thunderous I am deafened in a moment. Wrenched downwards, the world flung away—

Hissing nothingness in my sensitive ears—

Half-open eyes to look upward one last moment as raging cataclysm boils its way forward, forward, forward—

Skin burnt and atomized, bones swept away to ash, feathery quills and scaly armor obliterated-

[theriodont]

The Day the Dinosaurs Died

The causes of the K-T extinction -- a massive asteroid impact some 65.5 million years ago and the resulting worldwide climatic disruptions and trophic collapses -- have been known for some time. Besides the rather dramatic and sudden change in what sorts of creatures turn in up in the fossil record -- the way large, diverse archosaurs dominated land environments and various sorts of other reptiles dominated marine environments until they all vanish at the same time got impossible not to notice after a while -- there are also the huge, buried crater in the Yucatan and the worldwide layer of iridium-rich deposits and tektites (small bodies of glassy minerals formed from material flash-melted and frozen mid-air during asteroid impacts).

Now, what had been missing -- until this March of 2019, obviously, or I would probably not be writing this to begin with -- was direct evidence of what happened during the disaster itself. Evidence of its effects is abundant -- direct evidence of what happened right at that moment, when the meteorite hit and its impact shook the world... not so much.

Our new evidence comes from Hell Creek, in North Dakota. It’s a fossil bed containing the jumbled remains of very diverse animals -- Triceratops bones, ammonites, mammals, tree material, fish and mosasaur remains have all been found in this single mass grave. Apparently, powerful waves swept through bodies of water and flung aquatic animals on land, devastating shoreline environments in the process. The mixed remains of aquatic and terrestrial life were then buried in sediment from successive waves.

(The waves, apparently, aren’t likely to have been direct tsunamis from the impact -- rather, the researches working on this site think them to have been seiche waves, which are caused by seismic tremors even very far from the source epicenter.)

The quickness of the event was apparently such that the remains were preserved with minimal damage -- the detritus would have flowed quickly and set just as quickly, allowing minimal scattering and crushing and thus permitting a high degree of preservation. Some of the remains are amazingly well preserved -- there’s even a fish that was clearly broken in half after hitting a tree.

Trace fossils are also present -- mammals burrows and dinosaur tracks were both preserved.

One of the most fascinating parts of this, to me, is the presence of tektites in the gills of the fish found in this bed, as well as in amber deposits within it. The causes are obvious enough -- as the glassy material rained down on the landscape, it would have fallen into the water where it would have been breathed in by fish and remain lodged in their gills, likely contributing to their deaths, and likewise on the forests that would have dominated the Hell Creek area at the time and lodged itself in tree sap that, over time, hardened into amber. These things, together, probably preservation the most specific view of a single moment in time -- the most specific event -- in this entire treasure trove.

Another thing to keep in mind: while the Hell Creek beds have generally yielded a very through cross-section of their ancient biodiversity compared to other sites, fossilization is always a very hit-or-miss process, and it’s extremely rare for a creature to die in just the right place and conditions to be preserved. The fossil record in inherently a very incomplete thing. Mass death events like, where an entire community is killed and preserved together by a single event, tend to be some of the most complete reputations of prehistoric environments by virtue of almost nothing having the chance to escape whatever disaster is burying almost every living thing at once -- think of the Burgess Shale. This mass grave, from what I understand, seems like it might end up yielding a few surprises once there will have been time to study it more thoroughly.

This is easily the most fascinating discovery of the past few years.

(I’ll be adding my sources in a reblog -- I’m not sure if Tumblr undid the thing where posts with external links don’t show up in searches, and I’m not taking risks)

[cretaceous-kid]

'cause you're hot

then you're cold

[xyhor-dinosaur-clade]

Only 13 percent of Earth’s surface is made up of rocks that could have caused such a huge extinction event, a new paper argues