Dino impact gave Earth the chill

BBC NEWS ^ | 05/31/04 | N/A

[TigerLikesRooster]

Dino impact gave Earth the chill

A cloud of sulphate particles may have blocked out the sun's warmth

Evidence has been found for a global winter following the asteroid impact that is thought to have killed off the dinosaurs 65 million years ago.

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.

Sun block

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.

The impactor theory is the favoured candidate for the demise of the dinosaurs

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.

Heat 'switch'

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.

[TigerLikesRooster]

One more piece of the puzzle, called "The Extinction of Dinosaurs by Asteriod Impact."

[gorebegone]

I think it was something else being spewed out that caused the climate to warm.

[TigerLikesRooster]

Re #2

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.

[spetznaz]

I watched a documentary on the Shoemaker-Levy-9 impact on Jupiter that occured in 1994 (I believe it was 1994), and it was really interesting. They said that the energy expended was equivalent to a Hiroshima-sized detonation, every second, for 13 years. And that the dust could caused by the impacts were greater than the size of the Earth.

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!

[Arthur Wildfire! March]

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.

[TigerLikesRooster]

Re #4

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.

[spetznaz]

Thanks for the post TLR. Saved me some head-wracking time trying to remember what volcano caused the temp change (I thought it was Krakatoa, but wanted to make sure).

Oh, and I see you can't sleep either. LOL.

[spetznaz]

Yep ....as you know, it has to be GW's fault! 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.

[JohnBovenmyer]

Actually Krakatau was only the 2nd largest volcanic eruption of the 19th century. The "year without summer" usually refers to the results of the 1815 eruption of Tambora, which was the largest volcanic eruption in recorded history.

[Junior]

TUCvER ping.

[PatrickHenry]

PING. [This list is for the evolution side of evolution threads, and some other science topics like cosmology. FReepmail me to be added or dropped.
Long- time list members get all pings, but can request "evo-only." New additions usually get evo-pings only, but can specify "all pings."]

[PatrickHenry]

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.

This is interesting as a method of spreading "local" species around. It wouldn't happen often, but apparently it does happen.

[Alamo-Girl]

Thanks for the ping!

[VadeRetro]

One problem with the pumice raft. You don't want to catch it at the launch point.

[TigerLikesRooster]

Re #12

Yeah, that is an interesting way to look at it. I came across no one who mentioned it as a means to spread species.

[Diamond]

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.:)

Only by ballpark mentality radiometric dating methods, which are notoriously unreliable. The Dropout can only be a few thousand years old at most.

Cordially,

[BartMan1]

Krakatoa.

But I think early 1800's.

[PatrickHenry]

One problem with the pumice raft. You don't want to catch it at the launch point.

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.

[RussianConservative]

What is pumice?

[VadeRetro]

Pumice is a frozen-foam lava. Often it is less dense than water.