Impact that killed the dinosaurs?
- Thread starter Brian G Turner
- Start date
Sorry just a. thought
On thing I have read is that major extinction occurs on average 25 millions or so years ?
"In this instance, DePalma alone of all the world's geologists has found an exact record of the exact day of the asteroid impact".
No, Melanie During makes the same claim for the same site, and her work is not in question by the paleo community.
I have no opinion with regard to DePalma's work and, for example, do not know whether Dakotaraptor was a chimera. A single misidentified furcula later corrected, would not have invalidated it. The rest of it, who knows...
"Yeah, I was in danger of being personal and for that I apologize".
Thank you, accepted and I appreciate that. Having been Technical Director on one paleo documentary and having advised on several others, I no longer watch paleo TV stuff. I was so disappointed by the one I spent 80% of my time on for two years that I didn't sign the release for footage of me to be used, and I never watched it after completion. I also got tired of being called for twenty minutes or so of advice during the production of other documentaries and then having my comments misinterpreted (through ignorance and/or limited budgets, not deliberately).
I tend to avoid the glossy magazines for the same reason - with the exception of some of National Geographic's stuff. Some of the paleo artist's work is very good; some not. For example, John Conway and John Sibbick are both superb. They listen and also have in depth background knowledge of their own that serves them well.
Most of the little that I know about paleo comes from personal contacts with others who work in the field, not from the literature (with the exception of the stuff I read when asked to do peer reviews prior to publication in the research journals). And like the media, some of the stuff published in the journals is good. Some ain't.
No, Melanie During makes the same claim for the same site, and her work is not in question by the paleo community.
I have no opinion with regard to DePalma's work and, for example, do not know whether Dakotaraptor was a chimera. A single misidentified furcula later corrected, would not have invalidated it. The rest of it, who knows...
"Yeah, I was in danger of being personal and for that I apologize".
Thank you, accepted and I appreciate that. Having been Technical Director on one paleo documentary and having advised on several others, I no longer watch paleo TV stuff. I was so disappointed by the one I spent 80% of my time on for two years that I didn't sign the release for footage of me to be used, and I never watched it after completion. I also got tired of being called for twenty minutes or so of advice during the production of other documentaries and then having my comments misinterpreted (through ignorance and/or limited budgets, not deliberately).
I tend to avoid the glossy magazines for the same reason - with the exception of some of National Geographic's stuff. Some of the paleo artist's work is very good; some not. For example, John Conway and John Sibbick are both superb. They listen and also have in depth background knowledge of their own that serves them well.
Most of the little that I know about paleo comes from personal contacts with others who work in the field, not from the literature (with the exception of the stuff I read when asked to do peer reviews prior to publication in the research journals). And like the media, some of the stuff published in the journals is good. Some ain't.
Last edited:
"On thing I have read is that major extinction occurs on average 25 millions or so years ?"
I got no opinion about that either. There's a 5km impact on average about every 20 million years, but that would only have about one eighth the energy of Chicxulub, so I wouldn't expect extensive damage to be worldwide (that's just a personal opinion, unsupported by quantitative data).
I got no opinion about that either. There's a 5km impact on average about every 20 million years, but that would only have about one eighth the energy of Chicxulub, so I wouldn't expect extensive damage to be worldwide (that's just a personal opinion, unsupported by quantitative data).
Last edited:
Matteo
Well-Known Member
- Joined
- Aug 8, 2012
- Messages
- 1,347
Not sure about the 25myo, but if I remember my studies (quite some years ago) the geological record is full of extinctions - some greater than others - and, basically, the time periods are split according to those extinctions.
I found this on the Chicxulub impact tsunami. There is a video towards the end of the report that give a more visual view.
The Tsunami that Killed Dinosaurs! | Coastal Processes, Hazards, and Society.
The Tsunami that Killed Dinosaurs! | Coastal Processes, Hazards, and Society.
Interesting stuff but rather filled with superlatives. And also some pretty careless writing like "The crater has a diameter of 200 km and a depth of about 1 km, a giant hole in the ground that slowly filled with seawater over a period of hours. This wasn’t a slow seeping in of water, it was a massive surge, huge waves of water entering the crater." (My highlighting)
The geological periods were first named around the abundance, or not, of the types of rocks and of fossils present in the record. So, while they didn't know that at the time they were naming them, as you say, the end of an abundance of a certain type of fossil marks a mass extinction. And mass extinctions must be related to some huge extra-planetary or volcanic/geological events in order to have affected the climate of the entire planet at the same time. You would have to conclude that these were most likely to be impacts by very large meteorites, stray asteroids or comets (which would presumably become less and less common over geological/astronomical lengths of time) however, there could be other reasons - we still know little about the Sun and how its output changes over the very long-term - or we may have been passing through extrasolar dust and gas clouds. It might be that volcanic/geological events just happened for no external reasons at all.
This kind of science investigation is difficult because it is an incomplete data set; it therefore becomes very subjective, and will always bring a number of different views to the table. I'm very late to this party, but going back to the beginning of the thread, and then reading some of the absolute certainties posted here since, then I'd say that no one can say anything with anything like that amount of certainty. However, these mass extinction events were climate changes, atmospheric composition changes or poisoning, and in regards to the K-T boundary event, the fact that it matches with date of the Chicxulub impact (a crater outline so large it is still visible on a map of the world even today) well, I think it's difficult to see how this wasn't a substantial contributing part of the cause. However, that's just my own opinion.
In addition to the cenote ring, it is also currently visible as a difference in the color and amount of vegetation within the bounds of the crater.
"The crater has a diameter of 200 km and a depth of about 1 km, a giant hole in the ground that slowly filled with seawater over a period of hours. This wasn’t a slow seeping in of water, it was a massive surge, huge waves of water entering the crater."
The gravity anomaly map perhaps indicates the paths of high velocity erosive inflows as the crater refilled with silt and water post- impact (and one of them likely is also the result of the tail gouge of the incoming asteroid - which would then provide a path for the subsequent inflow as well). The sea was shallow at the location of the impact, and reasonable approximations could probably be made that would allow approximate inflow velocities and refill time to be calculated. I'm too lazy to do it myself, but it wouldn't surprise me to find that it would take several hours for the basin to refill with debris, silt, and water.
"The crater has a diameter of 200 km and a depth of about 1 km, a giant hole in the ground that slowly filled with seawater over a period of hours. This wasn’t a slow seeping in of water, it was a massive surge, huge waves of water entering the crater."
The gravity anomaly map perhaps indicates the paths of high velocity erosive inflows as the crater refilled with silt and water post- impact (and one of them likely is also the result of the tail gouge of the incoming asteroid - which would then provide a path for the subsequent inflow as well). The sea was shallow at the location of the impact, and reasonable approximations could probably be made that would allow approximate inflow velocities and refill time to be calculated. I'm too lazy to do it myself, but it wouldn't surprise me to find that it would take several hours for the basin to refill with debris, silt, and water.
Last edited:
Matteo
Well-Known Member
- Joined
- Aug 8, 2012
- Messages
- 1,347
Pretty ordinary in most fields of academia. 
I saw that too as I read it. Has an almost AI assisted feet to it. Or very hastily put together.
"a giant hole in the ground that slowly filled with seawater over a period of hours".
I didn't read the document, but how long did it take to refill, and how much time constitutes slowly?
As phrased, that statement appears to be referring to time rather than velocity or rate of flow.
I didn't read the document, but how long did it take to refill, and how much time constitutes slowly?
As phrased, that statement appears to be referring to time rather than velocity or rate of flow.
Well, curiosity overwhelmed me. I just did some very rough calculations based on loose assumptions that are subject to substantial error.
I came up with 83 hours to fill the basin with seawater and silt, assuming that the outer rim acted as a broad crested weir and the surrounding sea locally was about 300 feet deep. Incoming water velocity over the rim averaged a little over 50 feet per second, so was highly erosive. Incoming rate of flow was about 15,000 cubic feet per second per linear foot of rim perimeter. I consider this time estimate to be quite conservative and think it would probably fill much quicker (but still rather slowly in terms of hours required). A caveat - I didn't check my numbers or arithmetic and could be way off even if procedurally correct. And yes, I am aware of the potential errors in the assumptions I made.
I came up with 83 hours to fill the basin with seawater and silt, assuming that the outer rim acted as a broad crested weir and the surrounding sea locally was about 300 feet deep. Incoming water velocity over the rim averaged a little over 50 feet per second, so was highly erosive. Incoming rate of flow was about 15,000 cubic feet per second per linear foot of rim perimeter. I consider this time estimate to be quite conservative and think it would probably fill much quicker (but still rather slowly in terms of hours required). A caveat - I didn't check my numbers or arithmetic and could be way off even if procedurally correct. And yes, I am aware of the potential errors in the assumptions I made.
Last edited:
Jim. Is that based on just water or a water/ocean floor slurry at mid to lower deeps with water at the top of the inflow?
Just a thought that came to mind.
Just a thought that came to mind.
This was quick and dirty, so It's just water, but I am aware that at an average of 50+fps inflow velocity, the sediment transport will be impressive to say the least (fluid flow is how I usually make my living). I treated the crater volume as a slice of spheres at two different depths. Also, at 300 feet deep, the broadcrested weir equation is a bit out of its depth (sorry, couldn't resist).
Similar threads
-
-
-
-
-
Interesting thought experiment on impact on global weather of vast numbers of solar panels
- Started by Montero
- Replies: 13