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Green Baron

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Everything posted by Green Baron

  1. Ooops, i see, thanks :-) Nothing ? Goodenough !
  2. That looks too high for proper impact landing, or it is a helicopter ? Whatever, i bet few can pronounce this one correctly: Aachen (in the corner between Germany, Belgium and the Netherlends)
  3. @kerbiloid: I just read it up. Though the book is about vertebrate evolution in general Benton dedicates ~8 pages to the extinction event, discussing gradual as well as catastrophic models because it is much under research. Most has been said already here, as @MinimumSky5 said, it is not easy and the record is not equally well everywhere. It is especially difficult if not impossible to identify survival rates and reasons of certain groups among others, as nearly all groups marine and on land where affected, but reptiles in general and plesio-, ptero- and dinosaurs in special got an obliterating blow (100%), but birds and marsupials where cut by 75% as well, if that pleases you :-) Ichtyosaurs were already gone by the mid of the Cretaceous, pterosaurs and plesiosaurs and other groups like mussels, ammonites, had already contracted before the event. Some situations like the in the OP show a catastrophic event, lasting hours to months, others a more gradual, spanning up to 5-10 million years. If this is a view on reality or an artefact because of the find- and dating situation is an open question. I won't go in detail about dating methods and other uncertainties because derail and so :-) There are ~200 K/Pg profiles worldwide, marine or terrestrial, though by for not all with fossils, and all show the same sequence. :-)
  4. Exactly. The focus on North America in the late Cretaceous is an artefact that narrows the global view on dinosaur diversity, that is correct, but actually clades had declined before the event, groups from their "high time" in the late Jurassic and early Cretaceous were already gone. But you are right, there still was enough diversity among them, Ceratops and Hadrosaurus roamed about. https://www.researchgate.net/publication/278018238_Diversity_of_late_cretaceous_dinosaurs_from_Mexico https://www.nature.com/articles/ncomms1815 ----------- Ah, look at that. A surprisingly fresh work supporting your argument (again North America) even suggests little diversity decline, from climate and niche modelling (open access): https://www.nature.com/articles/s41467-019-08997-2 Interesting, interesting (starts reading) :-) Ok. Less spectacular than i thought. The main thing that's missing now are find sites, deposits, to document a similar diversity in the upper Cretaceous like in the Jurassic and lower C.
  5. Possible misunderstanding between us here ? An object smaller than the moon could have existed in an earth-moon Lagrange point after the collision, migrated over a few hundred million years through instabilities caused by other bodies around and collided with the moon and created the maria (very hypothetical, they may be just basaltic flows caused by density differences or smaller impacts). But "Theia" did not originate in an earth-sun Lagrange and migrated towards earth. It was probably just one of quite a few bodies of that size in the first 10s of millions of years that happened to cross earth's path. If the collision happened as hypothesized. I simply take my info from the publications i find on the matter and deem reasonable. Edit: unsure if the above is a valid thought at all. Maybe just nonsense so stroke it out. An impact simulation: https://www.sciencedirect.com/science/article/abs/pii/S0019103503002999 with peep show: https://sservi.nasa.gov/articles/evidence-for-moon-forming-impact-found-inside-meteorites/
  6. Sorry, your sarcasm makes it difficult to tell the info from the jokes. Nothing L point, no migration. We are under orbital mechanics. Things in the L point can not collide with one of the bodies because they are in resonance. It simply means that the moon is formed from earth's crust with possible mixed stuff from another body. And it did so in the first 10s of millions of years. No capture. Capture doesn't work. It is to the best possible degree under current knowledge, yes. And it explains the high angular momentum of the earth moon system as well, as one can read up. If you mean by "chemical features" the slight differences in isotopic composition, that's the catch for impact thing and still needs further explanation.
  7. Yap (Micronesia) A crab on that map of Yap.
  8. From the links upthread, the capture hypothesis (of an object that originated elsewhere in the protoplanetary disk) was dropped in the 80s in favour of the collision hypothesis because of two reasons: first, the dynamics for the capture are difficult to explain, the moon is simply too massive and would have been too fast to be captured by the earth without additional braking at the right time to enter an orbit. Second, isotopic composition (here: stable oxygen isotopes) suggest a common origin, from the same mass aggregation in that disk. apart from that, it lacks a core that objects of its size should have. The exact dynamics of the today favoured impact, if it was a glancing blow or a head on impact, if the material was completely vapourized in the event or not (that should actually be testable from the lunar minerals we have, was that done already ?), are in discussion. If you guys like, try to find info on the mineral phases of and conditions that formed the lunar minerals. Probably a lot of shock transformation from impacts. Just recently a paper was published (linked in the Random Science Facts thread i believe) that found a Zirkon in one of the moons samples with a clear signature from earth. The sample actually pushed the earth's age farther back than all the rock samples from earth itself. That little chip would then be an argument against the forming of the moon from a completely vapourized cloud. Would ... could ... should .. i should do something productive now :-) Haven't i said "i am out"
  9. 1934 Bugatti Type 57 3457
  10. @kerbiloid, when you're into reading, let me recommend https://www.amazon.com/Vertebrate-Palaeontology-Michael-Benton/dp/1118406842/ref=sr_1_1?crid=13SJ3JD2KG4BK&keywords=vertebrate+paleontology+benton&qid=1553977525&s=gateway&sprefix=benton+pal%2Caps%2C257&sr=8-1 University level introductory knowledge about creatures with a spine and how they are connected. You also get to learn methods like cladograms for example. Definitely a buy if these things interest you !
  11. That is relative. The late Cretaceous arctic probably was not colder than -2° at the lower range, and >15° in the warmer months. Before the late Cretaceous, temps were higher, a nice warm worldwide greenhouse, apart from isolated events with lower temperatures. They could have occupied niches up there when conditions were favourable. https://www.sciencedaily.com/releases/2015/05/150528083818.htm I have no reasonable idea ...
  12. i mean, @James Kerman, as a new moderator. An excellent choice.
  13. I doubt we can isolate single factors. For that the whole extinction scenario is too complex, too widespread, too encompassing, even contradictory. Especially the mentioned biome thing i love so much :-), i doubt it is quantifiable in terms of of causality without much simplification. A lot of simulation work has been published in the last years, dealing with he flood basalt and impact. It partly contradicts itself, (is cooling by sulphuric acid or sulphur dioxide stronger than warming through carbon dioxide ?), how fast where gases released ? Where organisms able to adapt fast enough ? Do we have a worldwide continuous record of fossils to judge the global effects or is it limited to regions ? Even a supernova in the vicinity has been checked as a contributing factor, but afaik the idea was discarded. How do the effects add up ? Or cancel themselves out ? Are there positive feedbacks ? Thresholds to activate sinks and wells for stuff ? Circulation pattern changes ? Gradually or abruptly ? Continentally or globally ? Evolution is not uniform in all organisms, some evolve faster, others are more stable, the rate can change over time. Species come and go naturally. Faster evolving organisms may occupy new niches more quickly. It is quite to easy to lump everything together and say global cooling + flood basalt + impact = bad, but for a detailed answer i doubt we know enough. Valid until correction :-)
  14. Writing out of the wrist, where is the salt shaker ... :-) Many taxa, especially the individually huge ones, where already gone long before the K/P event, eventually with the continental breakup. - Living spaces became restricted, biomes smaller and more diversified - Global cooling through increased weathering rates (an underestimated effect because it is soooo slow, but effective !) - Deep sea trenches, less shallow, warm sub continental waters - Flood basalt (another very effective cooling "method"). - Impact (was that necessary at that time :-) ?) - Beginning glaciation, albedo rising - Mammals may be more effective to regulate body temperature. Fur is a better insulator than scales. Not everybody had feathers ... - Food chains disrupted in changin' times - others ?
  15. Beautiful fossils ! My 5 cents: Chixchulub was a continental disaster and possibly the "last drop for the cask to spill over", for the environmental collapse to happen. Flood basalt had a much larger global impact on an already stressed environment, and for a longer time. The monstrous plant eating dinosaurs had already disappeared at the time of the impact, their realm being more and more constrained presumably by the continental breakup that disrupted large connected living spaces into smaller ones. Hadrosaur traces were found in Europe above the iridium layer of the impact, but this is debated. Many of today's dinosaur finds are from America, and there is a clear distinction between below and above the boundary. But i would not be too surprised if for example Chinese palaeontology one day presents us dinosaurs from the lower paleogene ...
  16. OneWeb satellite lost ? Really ? I thought it was successfully launched on 27.th of February ? Where am i wrong ?
  17. I am actually wasting explanations, time and effort. I am out.
  18. Maybe among others, resonance. Trojans are in a 1 to 1 resonance. A planet has flung objects that were crossing its path in- or outside, or in the course of multiple encounters they were set on a resonant orbit that never takes them near enough for an impact or encounter. This does, of course, not exclude other influences on these bodies, like other planets or disturbances from outside, which might set such an object on an encounter or collision course again. To the "circular reasoning", to exclude that we say a hypothesis must be testable. We do have tests for the Theia thing, orbital motion was mentioned and geo- and lunar chemistry (which triggered the idea in the first place). More indirect evidence include the history of the solar system and the "unrulyness" of its first inhabitants :-), will say violent conditions in its early days. (Though, as a sidenote, the LHB (late heavy bombardment) hypothesis, a similar but less well tested assumption, is about to be laid to the archives of science.) Nobody sticks to a hypothesis longer than is necessary, but to be released something better must be presented. You may have noticed that i found your OP interesting if not widening the view on the moon's formation. I would simply wait for remarks and discussions it may trigger, if it triggers. No. We have ~400kg of samples from different places, the landing sites of the Apollo missions. And these samples were only the triggers, as i and others wrote 10 times now, there is more evidence to the giant impact hypothesis. And your link does not exclude it, it extends it, and is only based on modelling, no hard data. Say, what it is that holds you back from accepting the inevitable .-) ?
  19. Mountains are a MUCH (!) younger thing. Allow me to give you some terms to set out for a little research yourself: During the time of the impact, at the beginning of the Hadean eon, the earth was "mushy", there was no continental crust. Mantle convection may have actually have been much faster than today. Forming of continental lithosphere started later, during the Archaean eon, when many small shifting and drifting cratons re- and arranged themselves over a softer mantle than today, which was convecting faster, and exchanging the surface more frequently. What came out of the water became subject to weathering, its products were and are lighter than oceanic (basaltic) crust because of a higher porosity, it starts to swim upon the basaltic underground, accretioning in larger "islands", that get welded together because of the crustal movement, forming the nuclei of future continents. This process, lasted for ~2 billion years, at the end of the Archaean ~70% of today continental crust was formed. Then, with the further cooling of the mantle, what we call "modern plate tectonics" began, sutures formed where the oceanic crust had cooled and densified so much that it tore off from the adjacent lighter continental crust and began to dive down through the mantle, dragging the oceanic crust behind it. Plates formed, and in exchange for the drag ocean ridges emerged where likewise magma erupted and erupts. The smaller proto-continents, unable to dive down again because of their buoyancy, arranged themselves at least 2 times in supercontinents. This process is running until today, and maybe for another ~500 million years, until the mantle has cooled down so much that subducting plates get stuck in the transition layer between crust and mantle. Ok. That is a short history of the earth. Mountains (here: Orogeny) is connected with the forming of supercontinents. Several phases of orogeny ore known, the penultimate one is known as the Variscan orogeny in the course of the forming of Pangaea, the actual orogenic period is better known and divided into as the forming of the Alps and Himalaya, the Andes and the two north American mountain ranges. These ranges emerge when a subducting plate (slab) becomes too heavy in the mantle, tears off and because of the "sudden" gain in buoyancy the overlaying continental crust rises too fast to be weathered away. Et viola: mountain ranges that quite well mark the main subduction zones. Also, if it hasn't been said already, while continental crust stays on the surface, oceanic does not get older than ~180million years (less than 5% of earth's age) before it gets subducted again. So, apart from a few ophiolites, Jurassic ocean floor is the oldest on earth. tl, dr: That process that builds up mountains did not exist in earlier times. -------------- If you have questions, here we are :-) Edit: ignore the link, it is for the advanced, presented in a much too sensational way. Like, really. It has nothing to do with mountains on the surface, as i hope i have transported in my compressed semester earth's internal dynamics :-)
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