A multiple fragment, thermal impact, comet firestorm that may have contributed to the Younger Dryas cooling, and the mega-faunal extinctions 12,900 years ago.
I was trained to do battle damage assessment in the military. And it has been an interest ever since. A long time ago, when the first LandSat images became available to the general public, I noticed some explosive blast effects that, in light of the new image data, couldn't be believably explained by standard geology theory. At the time, I knew nothing of the Younger Dryas cooling. And it was before any talk of a proposed impact event at the end of the last ice age. But it was a wonderful conundrum. I knew I was looking at the results of a continental scale natural disaster that flew in the face everything I had ever learned. I knew of no natural energy release to account for the scale of blast effected materials I was looking at. And for that matter, I knew of no kind of energy release at all that could do what I was seeing.
By "blast effected materials" I mean to say any material which owes its present location and/or chemistry to an explosive event. If a rock is strong enough to withstand the force of a nuclear blast with nothing but a burn mark, then even though it didn't move, that burn mark makes it a blast effected material. If a rock was melted, and emplaced, in an explosive event, the nature of the explosion that melted, and moved, it gets faithfully recorded in the lines of movement frozen into the flowing stone. Learning to read those lines of flow is more about fluid mechanics, and blast analysis, than anything else. But we are all descended from the most successful hunter-gatherers who ever came down out of the trees. Those who couldn't see which way their dinner went, didn't eat. As a result, good pattern recognition skills, and tracking abilities are innate human traits. And tracking the movements of those flows of melted stone is literally so easy a child could do it.
The ground effects, and blast effected materials, I had noticed all seemed to point to something that happened around the end of the last Ice age. And, when I learned of work on the Younger Dryas Boundary layer, and the nano-diamonds R.B. firestone et al, and others had found there, I realized they confirmed some of what I had found. It confirmed, if nothing else, that an event of the level of destruction I was considering did indeed happen. And recently enough too.
But when we consider all of those factors at the same time we come to an uncomfortable paradox. There should be a lot more impact structures; big ones, clearly visible, with little or no erosion. In fact, there must be at least one major mountain range on the Earth, however old, or deeply eroded, that owes its very existence to an extra-terrestrial impact or explosion. And yet, there is not a single accepted theory that allows for extra-terrestrial events as one of the possible driving forces in landform creation.
To be fair, in all of recorded history there hasn't been a single significant ballistic cratering event like we see in the simulations. We don't even hear about a classic, ballistic cratering, impact event like the simulations show in the archetypes of our most ancient of myths, and legends. But the firestorm of mass extinction impacts that wiped out North America a few thousand years ago did happen. We have the burned bones of the corpses for proof. And we have other materials that tell us conclusively of the heat and pressure that must have happened at some places in the firestorm. Such heat and pressure as is only found in an ET impact event. Those specific materials are the nano-diamonds found in the Younger Dryas Boundary layer (YDB). (Firestone et al 2007, Kennett et al 2008,2009) They are important for the fact that they weren't brought here. Rather, they were formed in the atmosphere during the violent explosions of multiple comet fragments. And the heat, and pressure, required to produce them makes them a valid proxy for understanding the atmospheric conditions they formed in. They are a barometer, and pyrometer, rolled up into one.
The nano-diamonds originated in unimaginably hot, and violent, above ground explosions, right here in the skies of earth. And Nano diamonds being found all over the world just means the violent conditions of heat, and pressure, it takes to form them are not uncommon at all. It doesn't make the detection of their existence any less significant. It makes it more so. When you hear ancient legends of a fiery rain of stones, or fire coming down from the sky, you are hearing an oral history account of a nano-diamond producing, thermal impact, event. The widespread detection of them confirms those ancient stories as having their roots in actual history, not mere myth.
The fragmented impact hypothesis as a trigger for the Younger Dryas cooling, and the megafaunal extinctions at the end of the last ice age has been criticized by some because of problems with a large object being able to be broken up in the atmosphere, and dispersed over a large landmass without any of the fragments being big enough to make an impact crater. And many of the critics cite the supposed strength of an asteroid. To the best of my knowledge, detailed analysis of the structural integrity of an asteroid has never been done. But It's probably true the atmosphere shouldn't be able to do that to a really big, fast moving, solid rock before any of it gets to the ground. We aren't talking about a dense, rocky asteroid that broke up when it got here though. We are talking about a fragmented comet. The Deep Impact mission to comet TEMPEL 1 showed the head of that comet to have the consistency of a dirty snow bank. It also showed that the object is a geologically active body. Comet HOLMES is unstable, and prone to violent outbursts. And if we look at the recent HST images shown at the top of this page of the fragments of Comet LINEAR, Or of the video clip of Schwassmann - Wachmann 9 we clearly see that explosive fragmentation of a comet can occur spontaneously before it even gets close to a planet. It doesn't need the atmosphere to do that.
And In a 2010 paper By William M.Napier of the Cardiff Center for Astrobiology, Cardiff University, UK., and published in the Journal Monthly Notices of the Royal Astronomical Society titled, Paleolithic extinctions and the Taurid Complex we read
" The proposition that an exceptionally large comet has been undergoing disintegration in the inner planetary system goes back over 40 years (Whipple 1967), and the evidence for the hypothesis has accumulated to the point where it seems compelling. Radio and visual meteor data show that the zodiacal cloud is dominated by a broad stream of largely cometary material which incorporates an ancient, dispersed system of related meteor streams. Embedded within this system are significant numbers of large NEOs, including Comet Encke. Replenishment of the zodiacal cloud is sporadic, with the current cloud being substantially overmassive in relation to current sources. The system is most easily understood as due to the injection and continuing disintegration of a comet 50-100 km in diameter. The fragmentation of comets is now recognized as a major route of their disintegration, and this is consistent with the numerous sub-streams and co-moving observed in the Taurid complex. The probable epoch of injection of this large comet, ~20-30 kyr ago, comfortably straddles the 12.9 kyr date of the Younger Dryas Boundary.
The hypothesis that terrestrial catastrophes may happen on timescales ~0.1 Myr, due to the Earth running through swarms of debris from disintegrating large comets, is likewise not new (Clube & Napier, 1984). However the accumulation of observations has allowed us to build an astronomical model, closely based on the contemporary environment, which can plausibly yield the postulated YDB catastrophe. The interception of ~1015 gm of material during the course of disintegration is shown here to have been a reasonably probable event, capable of yielding destruction on a continental scale.
The object of this paper is not to claim that such an encounter took place at 12,900 BP – that is a matter for Earth scientists – but to show that a convincing astronomical scenario can be constructed which seems to give a satisfactory match to the major geophysical features of the Younger Dryas Boundary data.
If indeed the YDB event was an astronomical catastrophe, its occurrence bears little relation to current impact hazard assesments derived from NEO surveys."
In fact it will be seen that the younger Dryas impacts were vastly different from anything described by current impact theory. And more violent than anything ever imagined.
Mark Boslough, at Sandia Labs has done a super computer simulation that depicts the atmospheric effects of an above ground blast like Tunguska but much larger. It shows the object exploding high in the atmosphere. But it retains it's momentum. And, in a moving explosion, all of the kinetic energy continues on down to the ground in the form of a supersonic downdraft shock wave hotter than the surface of the sun. Dr. Boslough's simulation depicted a single object. I will show that the Younger Dryas Impacts were two clusters, each hundreds of miles wide, and consisting of tens of thousands of objects such as that.
For comparison, an ordinary oxy-acetylene cutting torch in a steel shop uses a thin stream of hot gases at only about 1600 degrees F. and 40 PSI. to cut steel. The speed of that stream of hot gasses is only a little bit more than a stiff breeze. But that's all it takes to turn solid iron into a melted, aerosol spray. And to blow it away in runnels of melt into heaps of slag. The nano-diamonds in the YDB are significant in that they formed under hot, violent, explosive, atmospheric conditions all over the north American continent that should have been able to do that to whole mountain ranges. Those conditions of intense heat, and pressure can only happen in an impact event. And yet no one has ever found a crater. But that much heat, and pressure, only goes away peacefully in children's bedtime stories. So, since the surface scars the impact firestorm made must be here right under our feet, then maybe the pretty, perfect circle, craters we see on the Moon, and Mars, and that we’ve come to assume we should expect here on Earth as well, aren’t what we should be looking for at all. But if we’re not looking for round craters, then what kinds of planetary scaring are we looking for?
There is a huge debate looming on the horizon. Because, in fact, many of the melted rock formations produced in the Younger Dryas impact event are very easy to identify, almost conclusively, with satellite images alone. And without exception, every one of the positively identifiable ET blast melt formations will be found to have already been mis-identified as volcanogenic.
Fire Cloud Rocks
I need to clarify how I am using the word 'ignimbrite'. If we break the word 'ignimbrite' down, and translate it literally to English, we get 'fire-cloud-rock' In the purest sense of the word, that definition holds up. But I am describing a vastly different kind of impact event. One that produced tens of thousands of square miles of sheat ignimbrites in North America by a thermal explosive process, of extraterrestrial origin, that has never been described before.
Untill now, Volcanic Tuff, and impact melt, have been the only known forms of ignimbrite. But there are three distinctly different forms of ignimbrite, not just two. They are each formed by different processes, that produce very distinct patterns of movement, and flow. All are emplaced as a blast effected material of a violent explosive event. And the recognizable differences are in the nature, and source, of the heat, and pressure, that produced the explosive forces. The different energies each produced unique patterns of movement, and flow, in the resulting 'fire cloud rock' at the time of its emplacement.
In an explosive volcanic erruption all of the rock erupts explosively from below the surface. The rock, as well as the heat, and pressure, it brings with it, share the same subterranean source. The pressure begins to dissipate very quickly with any distance from the vent. And It does not provide a motive force once the volcanic materials are on the ground. Once an ash cloud has collapsed, and the material falls to Earth, the only motive forces left to provide material movement are gravity, and momentum.
Produced in a ballistic/kinetic impact with the ground of a solid bolide. 'Impact melt' is another form of fire cloud rock. And it is often mistaken for volcanic tuff. But we see a dramatic difference. Because the source of the rock is the surface itself, mixed with what's left of the bolide. The heat, and pressure is produced instantaneously at the surface, and at the moment of impact. After the initial impact explosion there is no continued production of the heat source. And almost all material movement is provided by momentum.
There is a third kind of frighteningly common fire cloud rock or ignimbrite. Formed, and emplaced in a third, and vastly different kind of process from anything described before. This material is the work of a fragmented comet which collided with the Earth as clusters, and streams, of high velocity particles, and fragments, that exploded very high in the atmosphere. They weren't point explosions either. The momentum was retained, even though all of the kinetic energy is translated into heat. And it continues plowing downwards through the atmospher in moveing explosions, as super heated, supersonic, down-blasts like Tunguska 1908. But the Tunguska object arrived alone. And, at an estimated destructive force equal to only about 15 megatons of TNT, it was such a puny little thing.The Taurid Progenitor hit the Earth as a fairly constant stream of tens of thousands of fragments like that. Accompanied by clouds of particles down to the size of dust grains. It hit at a low angle of about thirty degrees comming from the shoutheast. And at a velocity of about 30 kilometers per second. Only the very first fragments fell into cold atmosphere. The rest fell into already superheated impact plasma, and just cranked up the heat and pressure. The down blasts were almost continuous until the last of the fragments fell, and the Earth finally moved out of the orbital path of the fragmented comet's debris.
The process probably lasted a little more than an hour. And the resulting heat, and pressure, of the intense impact showers ablated vast areas of the surface terrains of north. And accumulations of that geo-ablative blast melt are described as non-volcanic ignimbrite, or geo-ablative blast melt.
What all three of those forms of 'Fire Cloud Rock' have in common is that the moment of their formation, and emplacement was a violent explosive event. So that from a forensic point of view, we can say that all 'ignimbrites', by their very nature, are a 'Blast effected material'. It all goes to fluid mechanics, and studying how they moved, and flowed. The three modes of ignimbrite formation, and emplacement, each have distinct, and easily recognizable patterns of movement, and flow. And reading those patterns of movement, and flow is as easy as reading a dance chart.
The movements of an unconstrained fluid are defined by the forces moving it.
And for our purposes we'll need to refine that profoundly simple observation a little more and say that there are two fundamental forces to consider; gravity, and pressure.
For example, take a droplet of paint, and put it on a level surface. Then blow it around with a straw. That's a pressure driven fluid. It's characteristic patterns of movement, and flow, are the result of the motive force being behind the flow, and pushing it. It piles up at the low pressure areas on the periphery where the pressure is no longer strong enough to move it.
Next, tip the surface a bit and let the paint flow downhill. That'll be a gravity attracted fluid. Its patterns of movement, and flow, are consistent with the motive force being in front of the flow, and pulling it down hill. It doesn't work on level ground.
The lines of flow in an unconstrained, and driven, fluid will always be away from the driving force. Even if that fluid is melted stone being driven up hill. And when those lines of flow are frozen into a river of melted stone they become a permanent, reliable record of the nature of the forces that melted, and moved it.
A fun variation, if you want you involve children in the experiment, is to use runny oatmeal spread out on a cookie sheet. If you have the kids surround the Cookie sheet, and blow the oatmeal around with short, random, puffs of air thru a straw. You get the same flow patterns. This version of the experiment makes it abundantly clear that the pattern recognition skills required are so simple a child could learn to recognize the patterns of movement in a pressure driven fluid. The kids easilly learned to recognize, and even to direct, and control, the flow patterns of a pressure driven fluid. And I've learned that it's difficult to do good, objective, scientific, observation with oatmeal in your ear.
I can't overstate the fundamental principle here that, if you want to study an explosive event after the fact, you should look to the actual motions of the blast effected materials. It's as simple as asking; which way was it moving before it came to a stop? Was the flow pushed from behind by pressure? Or was it pulled from the front by gravity? Where did it flow from? This is a profoundly simple hypothesis founded on the principle that we can answer those basic, fundamental questions easily, and confidently, with hi-resolution satellite images alone.
The Chihuahuan Ignimbrites
I would have thought that the geology of the north American continent was all very well studied. But when you start looking for any detailed research on emplacement of the surface ignimbrites in central Mexico, and west Texas, and the exact nature of the explosive events they were formed in. You quickly find that, while there are quite a few untested theories, detailed studies of it's origins, and emplacement, haven't been done. But by understanding the motions, and fluid dynamics of the ignimbrites, and other blast effected materials, in the region we can come to a true understanding of the nature of the explosions they were formed in. The truth is clearly written in stone for all to see. We need only to get some altitude, and a little distance, in order to read it.
The mountain you see here is 5 miles long.
The mountain is clearly, and obviously, the source location for the radial out wards splash curtain of ignimbrites. But The mountain is not a volcano. It consists of uplifted meta-sedimentary rock. And there is no vent there. So it is not the source of heat, and pressure that melted, and moved them.
There are only two possible directions look to for enough heat, and pressure to melt a few cubic miles of the Earth's surface and to blow it away from its source. Since we can clearly see the ignimbrites didn't come out of the mountain. But were blown off of it, and away from it. We can rule out down.
So the heat, and pressure, to melt and move that radial ignimbrite curtain came from above.
Click here for an 8.5 meg high resolution image with the mountain in context with its.surroundings.
I have been told that "most Geologists agree" that these ignimbrites were deposited in the so called Mid-Tertiary Ignimbrite flair up between 25 and 40 million years ago. such an ancient date for the emplacement of these ignimbrites can't be supported.
The geochronology of the north American continent is still very poorly defined. And if we accept that the state of the science is expressed by the USGS's own Geochronological data-base, it just may be that we don't have the technology yet to accurately date this event. When I downloaded the database what I got was a huge spreadsheet in Microsoft Excel format with most of the cells left empty. They explain the empty cells with the disclaimer that they haven't included any of the anomalous data. And there aren't any entries for anywhere on the continent in the "age since melt" column...
They give no explanation of what they consider to be "anomalous data". And without such an explanation I have to consider that either most of their assumptions are wrong, or most of their data is questionable. And without free access to the whole dataset, warts, and all, I remain to be convinced of the validity of any of it.
But if we want to pretend, and maintain, that there was a vent there that the ignimbrites erupted from 25 million years ago, and that they, and the mountain they came from, have undergone so many millions of years of exposure to the elements, then the ignimbrites need to show a considerable amount of hydrologic decomposition. There should be nothing left of them but soils. And they need to be under 25 million years worth of alluvium from the erosion of the mountain. Instead, they are on top of everything else. And we see virtually no alluvium from the mountain at all. Only the mountain, and its radial curtain of ignimbrites, slightly dusted with wind born sediments.
The ignimbrites of the Chihuahuan desert, extending all the way up into west Texas, and New Mexico are on top of every thing else in perfect condition. They are the pristine capstone of the geologic column. And with the exception of that tiny amount of wind blown silt, and the occasional sage brush, this terrain did not look much different when the ignimbrites covering it were still hot, and smoking, the day after the event they formed in.
In an explosive volcanic eruption we see both gravity, and pressure at work as the material is ejected from the vent forcefully, only to be attracted by gravity down, and away from the vent. And it rarely flows very far. But we see something different going on in central Mexico, and west Texas. There are tens of thousands of square kilometers of pristine ignimbrites, with no visible signs of decomposition, at the very top of the geologic column. And when you spend some time studying the movements of the blast effected materials in the satellite images, you'll notice something that generations of Geologists on the ground missed. The patterns of movement, and flow are not consistent with a volcanic eruption at all. All of the material movement is pressure driven. And there aren't enough volcanic vents to account for even a fraction of all of the melted material. And, because of the scale of it all, you don't see it until about twenty thousand feet. But the simple, observable, fact is that, contrary to the old literature, the melt didn't come out of the ground in a so called ignimbrite "flair up". It was the original surface terrain, blasted, and flash melted, by multiple sources of heat, and pressure coming down from above. The material was blown off its source locations by those same above ground sources of heat, and pressure.
Click on the image for an enlarged view. Or if you'd like to see a wider perspective with this place in context with its surroundings click Here for a 4.5 meg PDF copy of the image.
The Sandia Lab's simulation didn't hazard a guess as to the resulting ground effects. But it is a fair assumption that instead of being smashed and recycled into a nice round ballistic impact structure, when the hyper thermal, supersonic, downdraft hits, the terrain below it quickly and violently just melts, and goes away like wax under a blow-torch. (Or like oatmeal away from a straw) We can logically predict that such an event should create a bare, ablated looking area or mountain surrounded by ignimbrites, and melted stone, flowing away from the blast epicenter.
The patterns of movement of the pressure driven, blast effected, materials are a proxy map for the atmospheric conditions above them. The blast melted rock settled into the low pressure areas after being flash melted, and blown off its points of origin. It can't get any simpler. Look closely. The lighter, smoothly melted stone marks the locations of the individual blast points and areas of highest heat, and pressure that the ignimbrites were driven off of.
Standing on the ground among those rocks, they are indistinguishable from ordinary volcanic tuff. Their true nature is only obvious from high altitude. It is only then that the words "volcaniclastic", or "volcanogenic" are revealed to be inappropriate.
Note that the ignimbrites are splayed out around the central peak in chevron shaped splashes like ejecta curtains.
The central uplift is all uplifted meta sedimentary rock. Not an eroded volcanic plug. Look closely, there is virtually no alluvium, or other products of exfoliation, or deterioration, of rock that we should expect if the surface of this terrain were millions of years old. Therefore the formation, and emplacement of the ignimbrites, is the most recent significant event in the geologic column.
Click on the image for an enlarged view. along the left edge We see two impact structures with radial fracture patterns like rock dings in a window pane. And we can tell by the patterns of movement in the blast effected materials that the objects impacted into still melted, not yet hardened, ignimbrites.
Ignimbrites blown outwards from a central uplift of meta-sedimentary rock such as you see here is ordinary-typical for most of the Chihuahuan Desert.
There has been some mapping of ignimbrites in the Chihuahua City area and on northward for about 100 km, or so, in spots along the Chihuahua-El Paso highway. It's taken years to get just that little bit done. But there is more than 40,000 square kilometers of pristine, random-colliding rivers of fast flowing ignimbrites in central Mexico, and up into west Texas that look like they only just cooled yesterday. Waiting a lifetime for those geologists on the ground was not an option. And in frustration because I couldn't get my hands on any decent research papers on the subject. I set out to work out the patterns of movement in the flows of tuff in north central Mexico for myself to get a better picture of the explosive events they formed in.
If it takes months, or years to map a few miles along a highway from the ground it's time to bring the work into the twenty first century and use the satellites our tax money paid for, and do it from space, or it'll never be finished. Thanks to NASA, Landsat, and Google, I can produce my own image map of any given area on the continent in full spectrum color with resolution down to 1 meter per pixel. And computer memory is the only constraint to size. I have a couple I've had printed professionally that cover a whole wall. If you look at a specific location anywhere in those flows it is very easy to see which way it was flowing at any given point. And backtrack it to its source location. A sheet of clear plastic, and a handful of markers, and you have a large area, hi-resolution flow map. Complete with little directional arrows.
Structure like this are prettty ordinary. And to one To one standing on the ground among those rocks who is well versed standard geology theory the assumption would be that the mountain was eroded to its present form over millions of years.
As with the mountains above; If the mountain were an ancient, eroded cindar cone of an eruption that produced the ignimbrites millions of years ago, that erosion should have burried the ignimbrites long ago under gentle rolling hills of alluvium, and sedimentary deposits.
There are gaping holes, and glaring discrepancies, in the data when it comes to the actual movements from it's assumed sources, and final placement. There simply aren't enough vents. And you can't say it came from one direction if it was flowing the other. Those actual material movements tell an extraordinary story. One that is far different from anything we ever imagined. It's abundantly clear that, sometimes, large scale surface melting can happen in a multiple air burst, thermal, impact event. And even though there may be no evidence of shocked minerals, we need to replace those generic terms of "deep crustal" and "upper mantle" with the actual temperatures, and pressures, the ignimbrites formed in.
The standard theory is that these materials were produced in multple events over a period of millions of years. But any given fragment of ignimbrite, no matter the scale of the event it formed in, was only in fluid state on the surface for a few violent seconds at most. Even in a super eruption that goes on for days. So if two flows of melted stone are representative of two separate events, even a separation of only a few seconds, then one of them will be seen to be over-topping the other, already solidified one. But if they were both melted, and flowing at the same time, the interaction between the two will be a fluid convergence. i.e. They will inter-finger. Or they will come together like two rivers flowing into one.
Everywhere, in all of the tens of thousands of square kilometers of random, colliding, flows of ignimbrites in central Mexico, and west Texas you'll note that, without exception, the patterns of movement in all of the materials are consistent with very fast, and sudden, motion like ejecta. And every collision between flows is a fluid convergence. There is not one single over-topping flow. The inescapable conclusion is that contrary to the old literature, all of the pressure driven ignimbrites in the Chihuahuan Desert were in rapid, fluid, motion at the very same time. All of that tuff describes an intricate, almost infinite, dance of violent fluid motions. And all of those turbulent, inter-flowing, motions describe the very same moment.
Either that material is the geologically recent result of the largest super eruption since primates first came down out of the trees. And most of central Mexico is one giant, explosive, caldera that no one ever noticed as such. And all of the missing vents will be found... someday. (And never mind that the simultaneous, inter-flowing, mega-flood of melted stone describes a sudden, virtually instantaneous, event.) Or all of the melt is the result of the most violent ET encounter in 65 million years. And it, and its ground effects, are different from anything ever studied before.
Both are pretty extraordinary possibilities. The visual evidence is more supportive of the latter. But no matter what the source of the heat, and pressure that melted ,and moved it, the more than 40,000 sq km pristine, simultaneous, random-colliding, inter-flowing, rivers of blast-generated ignimbrites, at the pinnacle of the stratigraphic column describes a geologically recent explosive event that was arguably the single most violent natural disaster in all of human existence. Yet, with the exception of a few prospectors looking for money rocks, it's almost completely unstudied.
It should be noted that no tomagraphic studies have ever revealed a single rifting vent such as those proposed for the Chihuahuan ignimbrites. And the actual source vents, and supergiant magma chambers, of the so called Mid Tertiary "Ignimbrite Flare Up" have never been found. They exist only in theory.
Scwassmann-Wachmann 3 for a pretty good example of a very recent, and currently continuing, breakup of a comet. Remember SL - 9? Before it impacted Jupiter, tidal forces had stretched the fragmented comet into a long stream of fragments, and particles. You should be getting a pretty good picture from those examples. Except that SW 3 is such a little bitty thing.
We get to celebrate the anniversary of the YD impact event every year with the return of the Taurid meteor showers. The most violent impact related catastrophe in 65 million years was caused by the multiple airburst impacts of the particles, and fragments of the Taurid Progenitor soon after it's total breakup. And as I've said, only the fragments on the leading edge fell into cold atmosphere. The rest fell into already superheated impact plasma. And they just cranked up the heat, and pressure.
The TP was a truly giant comet. Before its breakup it is estimated to have been between 50 km, and 100 km, in diameter. And had it impacted in one piece we would not be here. You can get hit fifty times with fifty pounds of force. And you can survive the ordeal. You may be bruised, and battered. But you stand a good chance of making a full recovery. But if all of that force hits in one blow of 2500 pounds, that'll be the end of you.
The impact showers began in the Great lakes region. And they finished in the Pacific Ocean, off the coast of California, when the Earth finally moved out of the orbital path of the comet. A major portion of the comet impacted in the first impact showers. But it wasn't through with us. It still isn't. And in the first few centuries afterwards, perhaps millennia, the Earth's annual passage through the comets debris stream would have been a devastating event to be anticipated, feared, and hidden from.