Nat Geo - Incinerator Earth

[Haddy]

Just saw this interesting show. Of course, there's no scheduled time for it to run again as yet, but catch it if you find it on again.

Naked Science - Incinerator Earth

65 million years ago an asteroid hit the Earth and wiped out the dinosaurs, but no one has ever known where the asteroid came from or how it killed off nearly three quarters of all life on Earth. This Naked Science episode uncovers alarming new evidence that the dinosaurs were doomed 100 million years before this catastrophic event. Following a group of maverick scientists, Incinerator Earth reveals what really happened; how life on Earth nearly came to an end; and what might happen if an 8-mile-diameter asteroid struck us again.

Read more: http://channel.nationalgeographic.com/series/naked-science/3494/Overview#ixzz0bZH9b8Pa'>http://channel.nationalgeographic.com/series/naked-science/3494/Overview#ixzz0bZH9b8Pa

http://channel.nationalgeographic.com/series/naked-science/3494/Overview

[Haddy]

http://channel.nationalgeographic.com/series/naked-science/3494/Overview#tab-Videos/07291_00

There's a video also but it seems to be a little buggy -- 5 minutes if you can get it to run

or more likely it's this stupid Win7. XP was so good....

Edited January 3, 2010 by Haddy

[Just Bob]

I justed watched that show also Sue. It was very insightful and well worth it to watch if it comes on again and you didn't see it.

[fig rocks]

Looks like it was a good one, hope I can catch it next time!

[Haddy]

Further recent info on firestorms / heat were just published in December of 2009.

Dinosaurs broiled, not grilled

Debris from K-T impact could have been heat source and heat shield

Ultimately, the Earth’s surface still felt like an oven on broil, but for only about eight minutes, the model suggests. The surface felt less heat for less time. This could explain why the species that survived the impact included small, burrowing mammals and aquatic reptiles like crocodiles that could take shelter from the searing heat, says Doug Robertson of the University of Colorado at Boulder.

“I’m really pleased about the model,” says Belcher, who says her research on the charcoal content of the boundary layer argues against widespread wildfires. “I think it’s been a long time coming.”

Robertson still believes worldwide fires occurred, however. While the radiation may not have been enough to directly ignite wood, it could still have kindled pine needles and dry leaves, he points out.

“You don’t need to ignite every tree to have a forest fire,” he says. “Toss a smoldering cigarette—it won’t ignite a log either, but it will ignite a forest fire. It’ll hit dry leaves, and poof.”

“It’s not a closed book on the wildfires,” Goldin says. “There’s still a lot of work going on, on both sides on this story, to converge on a solution.”....

Friday, December 11th, 2009

http://www.sciencenews.org/view/generic/id/50691/title/Dinosaurs_broiled,_not_grilled

That article is from Science -- here's the abstract from Geology:

Self-shielding of thermal radiation by Chicxulub impact ejecta: Firestorm or fizzle?

Tamara J. Goldin1,* and H. Jay Melosh1

Lunar and Planetary Lab, University of Arizona, Tucson, Arizona 85721, USA

As hypervelocity ejecta from the Chicxulub (Yucatán, Mexico) impact fell back to Earth, the surface may have received a deadly dose of thermal radiation sufficient to ignite global wildfires. Using a two-phase fluid flow code, which includes ejecta and air opacities in a radiative transfer calculation, we modeled the atmospheric reentry of spherules arriving at distal sites. The models predict a pulse of thermal radiation at the surface peaking at 5–15 kW/m2, analogous to an oven set on "broil" (~260° C). Previous calculations, which ignored spherule opacity, yielded >10 kW/m2 sustained over >20 min and such an extended pulse is thought to be required for wood ignition. However, the new modeling suggests that fluxes only exceed the solar norm for ~30 min and are only >5 kW/m2 for a few minutes. Previous models failed to consider the self-shielding effect of settling spherules, which block an increasing proportion of downward thermal radiation emitted by the later-arriving spherules. Such self-shielding may have prevented widespread wildfire ignition, although the thermal pulse may have been sufficient to ignite localized fires and kill fauna lacking temporary shelter. An opaque cap of submicron dust in the upper atmosphere could, however, override the self-shielding effect.

http://geology.geoscienceworld.org/cgi/content/abstract/37/12/1135

There's also another article in that issue that quotes this one (and you can read it in entirety here):

Reigniting the Cretaceous-Palaeogene firestorm debate

Claire M. Belcher

School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Ireland

Nearly 30 yr since Alvarez et al. (1980) detected an enrichment of iridium at the Cretaceous-Palaeogene (K-Pg) boundary (65 Ma), the events that lead to the demise of the dinosaurs have become a feature of considerable scientific and public debate. It is generally accepted that an extraterrestrial body collided with the Earth 65 m.y. ago and that the 200-km-wide Chicxulub Crater on the Yucatan Peninsula, Mexico, is the mark of this impact (Hildebrand et al., 1991). This impact blasted melted asteroidal and target rock debris across the planet, depositing the K-Pg boundary impact rock layers (Fig. 1). The environmental consequences of the impact, and particularly the amount of thermal radiation it delivered, remain the hottest topic of the K-Pg debate.

....

It is recognized that there was a major disruption to plant communities across the K-Pg boundary (Tshudy et al., 1984; Sweet, 2001; Nichols and Johnson, 2002). These new model-based results, taken together with the abundant literature on paleontological indicators of fire occurrence, suggest that extensive wildfires were not the cause. This model-data agreement does not eliminate the role of relatively high temperatures (on the order of a couple of hundred degrees centigrade) in some of the extinctions seen at this time; but does suggest that the thermal pulse component of the K-Pg impact was not as significant as has been previously thought. Additional mechanisms might be required to fully explain the K-Pg extinctions, in which the effects of an "impact winter" (Galeotti et al., 2004) followed by global warming (O'Keefe and Ahrens, 1989; Beerling et al., 2002), acid rain (Hildebrand and Boynton, 1989; Prinn and Fegley, 1987), and the additional stress of Deccan volcanism (Courtillot et al., 1988; Chenet et al., 2007) on the Earth system might be more fully investigated. It is clear that significant environmental perturbations would be expected following the K-Pg impact event, even in the absence of extensive K-Pg wildfires.

http://geology.geoscienceworld.org/cgi/content/full/37/12/1147

Edited January 5, 2010 by Haddy

[MarkGelbart]

I already dug a hole in my backyard in case something like this happens while I'm alive.