Skip to comments.Dino impact gave Earth the chill
Posted on 06/01/2004 1:02:01 AM PDT by TigerLikesRooster
Dino impact gave Earth the chill
Rocks in Tunisia reveal microscopic cold-water creatures invaded a warm sea just after the space rock struck Earth.
The global winter was probably caused by a pollutant cloud of sulphate particles released when the asteroid vapourised rocks at Chicxulub, Mexico.
The results are reported in the latest issue of the journal Geology.
Italian, US and Dutch researchers studied rocks at El Kef in Tunisia which cover the Cretaceous-Tertiary (K-T) boundary, when dinosaurs - amongst other species - vanished from our planet.
At the time of the dinosaurs, El-Kef was part of the warm western Tethys Sea. When the scientists studied the types of microscopic fossil creatures present in the Tunisian rocks, they found some surprising changes after the K-T boundary.
Firstly, two new species of benthic foraminifera - simple animals that live near the sea floor - appeared. These newcomers were cold-water types found in more northerly oceans.
Secondly, they found a curious difference in the shape of a microscopic snail-like creature called Cibicidoides pseudoacutus. This creature's shell is said to coil in either a left or a right direction.
In cold waters there are proportionally more left-coiling individuals, while in warmer waters this pattern is reversed. The researchers found a proportional increase in left-coiling Cibicidoides, after the K-T boundary.
"It's the first time we have found physical evidence for cooling at the K-T boundary," said Dr Simone Galeotti of the University of Urbino, Italy.
Dr Galeotti and his colleagues think the most likely cause of the cooling was a pollutant cloud of airborne sulphate particles, or aerosols, that blocked out sunlight.
These would have been released when the asteroid collision vapourised rocks rich in sulphate salts at Chicxulub.
Matthew Huber of Purdue University in Indiana, US, calculated the global impact of the winter.
"The results we got are fairly consistent with the impact winter decreasing the amount of sunlight hitting the Earth by 90%. If you turn off that heat source, the Earth will cool in a big way," he told BBC News Online.
The oceans would have acted as a reservoir of heat to prevent the surface temperature of the planet from cooling too much. However, this reservoir is not infinite. If the sunlight was blocked out for long enough, the oceans would eventually have frozen solid.
"It must have been dark long enough to cool the oceans, but not long enough that the whole planet iced over - that's not what we see in the fossil record," said Dr Huber.
This impact-induced darkness would have lasted between one and ten years on land, but there is evidence for a cooling of up to 2,000 years at El Kef.
Positive feedback mechanisms may have prolonged the cooling effect of the impact winter in waters of intermediate depth - such as those at El Kef - and deeper.
The Cretaceous-Tertiary extinction was a selective one; entire groups such as dinosaurs and ammonites were killed off, while others were left unaffected.
The latest research does not probe this mystery, but it does help fill in the picture of what was happening to our planet following the impact at Chicxulub.
Never realized that Al Gore is 60 million years old. After 60 million years of constant trying, he finally managed to get into Harvard a few decades ago.:) The oldest student ever to get into that school, but nobody had noticed.
Now, if the dust cloud can be that large, then it can be assumed that a huge meteorite hit (not necessarily something as big as the ShoemakerLevy9 comet that impacted Jupiter) could be counted on raising a sizeable dust cloud that would change life as we know it.
In the late 1800s there was a volcano explosion (with time i will recall the name of the mount) that caused parts of Europe and the US to experience a whole year without summer (due to the volcanic ash changing the climate patterns for the year). Imagine what an asteroid/meteorite/(God-forbid)Comet could do!
The astoroid was sent here by Halliburton, which is secretly run by a small but greedy race of space aliens who later returned to drill the oil the dinosaurs produced.
On a slightly more serious note:
Burning soft coal could stem global warming, I suspect, if things actually did get out of hand. Actually, though, I think third world countries already are burning a lot of soft coal.
Hi, spetz. That mountain is Krakatoa, which blew up in 1883. Here are some details picked up from Internet.
Krakatau erupted in 1883, in one of the largest eruptions in recent time. Krakatau is an island volcano along the Indonesian arc, between the much larger islands of Sumatra and Java (each of which has many volcanoes also along the arc). There is a very fine book about the Krakatau eruption by Tom Simkin and Richard Fiske, so if you really want to know about the eruption you should go to the nearest bookstore or library to find that. Here are some highlights from their summary of effects:
1. The explosions were heard on Rodriguez Island, 4653 km distant across the Indian Ocean, and over 1/13th of the earth's surface.
2. Ash fell on Singapore 840 km to the N, Cocos (Keeling) Island 1155 km to the SW, and ships as far as 6076 km WNW. Darkness covered the Sunda Straits from 11 a.m. Ont 27th until dawn the next day.
3. Giant waves reached heights of 40 m above sea level, devastating everything in their path and hurling ashore coral blocks weighing as much as 600 tons.
4. At least 36,417 people were killed, most by the giant sea waves, and 165 coastal villages were destroyed.
5. When the eruption ended only 1/3 of Krakatau, formerly 5x9 km, remained above sea level, and new islands of steaming pumice and ash lay to the north where the sea had been 36 m deep.
6. Every recording barograph in the world documented the passage of the airwave, some as many as 7 times as the wave bounced back and forth between the eruption site and its antipodes for 5 days after the explosion.
7. Tide gauges also recorded the sea wave's passage far from Krakatau. The wave "reached Aden in 12 hours, a distance of 3800 nautical miles, usually traversed by a good steamer in 12 days".
8. Blue and green suns were observed as fine ash and aerosol, erupted perhaps 50 km into the stratosphere, circled the equator in 13 days.
9. Three months after the eruption these products had spread to higher latitudes causing such vivid red sunset afterglows that fire engines were called out in New York, Poughkeepsie, and New Haven to quench the apparent conflagration. Unusual sunsets continued for 3 years.
10. Rafts of floating pumice-locally thick enough to support men, trees, and no doubt other biological passengers-crossed the Indian Ocean in 10 months. Others reached Melanesia, and were still afloat two years after the eruption.
11. The volcanic dust veil that created such spectacular atmospheric effects also acted as a solar radiation filter, lowering global temperatures as much as 1.2 degree C in the year after the eruption. Temperatures did not return to normal until 1888.
Oh, and I see you can't sleep either. LOL.
You know what .....don't be too surprised if the next James Bond movie has a Halliburton clone being the baddie's evil company. I wouldn't be surprised at all.
This is interesting as a method of spreading "local" species around. It wouldn't happen often, but apparently it does happen.
Thanks for the ping!
One problem with the pumice raft. You don't want to catch it at the launch point.
Yeah, that is an interesting way to look at it. I came across no one who mentioned it as a means to spread species.
Only by ballpark mentality radiometric dating methods, which are notoriously unreliable. The Dropout can only be a few thousand years old at most.
But I think early 1800's.
What really made Neanderthals go extinct:
Ogg: Look, fellows! That volcano is really looking serious. Let's swim away from here. Otherwise, all our people will die.
Gugg: Swimming is a lot of work. Let's wait until we get a pumice raft to float on.
What is pumice?
Pumice is a frozen-foam lava. Often it is less dense than water.
"Everybody loves somebody sometime..."
"Dust my pumice!"
One curious product of the Krakatoa sunsets was Edvard Munch's painting 'The Scream'. The sky behind the screaming figure display a devil's palette of strange colors. In the high latitudes where there is virtualy no night during the summer the sunset twilight produces curious effects during normal years. In the years after Krakatoa blew up the 'midnight sun' produced particularly lurid effects with the sky literally seeming to be ablaze for hours. Apparently Munch was one of many Norse and Swedes who were drivwn to almost mania by these atmospheric conditions.
So not only did he invent the Internet, he also invented the computers on which it runs and the network lines that connect it!
Dino impact gave Earth the chill, because he was cooool, baby.
No, It's just another example of media hound scientist grasping at straws trying to prop up what should be a long dead hypothesis.
1st - In regards to the so called Asteroid who cares what happened after the K-T event since there is increasing evidence that the Chicxulub crater predates the end-Cretaceous mass extinction by about 300,000 years. (More links here and here)
2nd, Dinoflagellates. Brinkhuis and Zachariasse (1988)record no accelerated rates of extinction across the K-T boundary in Tunisia.
So let me get this straight, The Sky was darkened which allowed the benthic foraminifera to move into a new area, Yet in that area Dinoflagellates who depend on sunlight and would be devastated in 6 months without it survived with no ill effects in the same area.
3rd, This is just one small area where there could be many reasons for a localized cooling effect. By focusing on one tiny area and ignoring the rest of world the scientist are being disingenuous at best.
In the rest of the world, Micro fossils show a different story, For example
a) Diatoms. The K-T event did not much affect the diatoms. Harwood (1988), based on studies from Seymour Island, eastern Antarctic Peninsula, the first to record siliceous microfossil assemblages across a K-T boundary sequence, notes that diatom survivorship across the K-T boundary was above 90 percent. Resting spores increase from 7 percent below to 35 percent across the K-T boundary.
b) Dinoflagellates. Dinoflagellates also were little affected by the K-T event (Bujak and Williams, 1979). Hultberg (1986) in Scandinavia records no accelerated rates of extinction across the K-T boundary . Danish dinoflagellates responded more by appearance of new species than by extinctions (Hansen, 1977), as did Seymour Island assemblages (Askin, 1988).
c) Yes other plankton did suffer massive extinctions but it wasn't because of the Asteroid or K-T event.
Marine calcareous microplankton, the coccolithophorids and planktonic foraminifera, were hit hardest of all by the K-T event. Thierstein (1981) proposes that the coccolithophorids extinctions were the most severe plankton extinction event in geologic history; via a "deconvolution" process, Thierstein (1981, 1982) reduced a Cretaceous-Tertiary "transition," in which Cretaceous assemblages were replaced by "new" Tertiary taxa, to an instantaneous catastrophe. Perch-Nielsen et al. (1982) note that the "catastrophic event"at the K-T boundary did not result in geologically instant extinction of the calcareous nannoplankton, and that most Cretaceous species survived the event. At DSDP Site 524, a sample above the K-T boundary contains 90 percent Cretaceous species. Isotopic analysis indicated that the Cretaceous species were not reworked specimens, but represented survivors of the K-T event that continued to reproduce in the earliest Tertiary oceans. The relict species became extinct some tens of thousands of years after K-T boundary time, probably via environmental stresses.
Finally, Microfossils were actually found in the Chicxulub crater itself!!! and even though they are essentially at "Ground Zero" they show no ill effects. So how could an Asteroid cause negative effects on life on the other side of the globe but not where it hit?
You can find pumice rock on the beaches of the eastern Mediterranean. It is like sponge and if you throw it into the sea it floats back on the next wave.
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