An era of skyrocketing global temperatures started with an impact bang according to research presented September 27, 2016, here in Denver at the Geological Society of America's Annual Meeting.
Impact debris and evidence of widespread wildfires in eastern North America suggest that a large space rock hit earth around 56 million years ago at the beginning of the Paleocene-Eocene Thermal Maximum, also known as the PETM, a period of rapid warming and huge increases in carbon dioxide.
The event is one of the closest historic analogs to modern global warming and is used to improve predictions of how earth’s climate and ecosystems will fare in the coming decades.
Too little is known about the newfound impact to guess its origin, size or effect on the global climate, said Dr. Morgan Schaller of Rensselaer Polytechnic Institute. But it fits in with the long-standing and controversial proposal that a comet impact caused the PETM. “The timing is nothing short of remarkable,” said Schaller at the GSA meeting.
The impact may have contributed to the rapid rise in CO2 by stirring carbon up into the atmosphere, but it was hardly the sole cause, said Sandra Kirtland Turner, a geochemist at the University of California, Riverside. Her own environmental simulations suggest that the influx of carbon that flooded Earth during the PETM probably took place over at least 2500 years, far too drawn out to be caused by a single event, she said at the same meeting.
During the PETM, a massive influx of carbon flooded the atmosphere and earth warmed by 5 to 8 degrees Celsius to temperatures much hotter than today. That carbon dump altered the relative abundance of different carbon isotopes in the atmosphere and oceans, leaving a signal in the sedimentary record.
While searching for that signal in roughly 56-million-year-old sediments from sites up and down the U.S. east coast, Schaller spotted microscopic glassy spheres about the size of a dust mite as seen in SEM:
These specks resemble those blasted from previously identified large impact events.
After switching from a black to a white sorting tray to more easily see the black debris, researchers discovered abundant charcoal pieces in the mix, as seen below in a Scanning Electron Microscope (SEM) image. That charcoal likely formed when wildfires sparked by the impact raged across the landscape.
These specks resemble those blasted from previously identified large impact events.
After switching from a black to a white sorting tray to more easily see the black debris, researchers discovered abundant charcoal pieces in the mix, as seen below in a Scanning Electron Microscope (SEM) image. That charcoal likely formed when wildfires sparked by the impact raged across the landscape.
More evidence of the impact will help researchers to better constrain its location, scope and possible relationship to the start of the PETM, Dr. Schaller said.
Have you ever made a simple change a la "black tray to white tray switch" to discover something new?
Steph
WE ARE CELEBRATING THREE YEARS OF PARTIAL ELLIPSIS OF THE SUN. . .
Have you ever made a simple change a la "black tray to white tray switch" to discover something new?
Steph
WE ARE CELEBRATING THREE YEARS OF PARTIAL ELLIPSIS OF THE SUN. . .
Another memorable GSA Annual Meeting in Denver happened in fall 1988 where and when John Hickenlooper passed out free beer coupons to geologists for his brand new micro-brewery, the Wynkoop.
ReplyDeleteNext year in Seattle. Anticipating The Big One?
DeleteMaybe so. GSA is such a fun, ground-breaking ;-) event. It's a very different vibe from the AAPG (American Association of Petroleum Geologists) annual meetings.
DeleteThe Geological Society of America meets in Colorado this year, in Washington state next year. I guess that's because being stoned is now legal in those states.
DeleteLegroan
You rock, Lego!
DeleteVery funny, Lego!
DeleteIs there evidence beyond those glassy spheres for a large impact event as the cause of the PETM? The Wikipedia page on the topic suggests that theory is controversial and lists several other possible causes. There isn't a smoking gun like the widespread iridium layer or Chicxulub crater for the K-Pg extinction, is there, or are those glassy spheres that distinctive? I'll just look into this microscopic crystal ball for the answer....
ReplyDeleteIt's a fairly new hypothesis and GSA is on the cutting edge. I don't believe researchers have yet discovered a crater comparable to Chicxulub and the K-Pg extinction. The glassy spheres do appear to be a key part of the hypothesis. . .
DeleteThat 275 mm diameter figure must be a typo. More like beach balls than microscopic. μm, maybe?
DeleteYes, I think it must be a typo for the diameter of the spheres. μm makes much more sense.
DeleteThe most striking graph for me is the one above (white background with blue and red curves) showing the PETM event with 2 billion metric tons of carbon per year and current data of 30(!) billion metric tons of carbon per year.
ReplyDeleteLooks like you get a comparable temperature rise in both cases. The area under the PETM curve is much greater, implying an ability to absorb a lot more carbon without greater temperature rise if you spread it out over a long period of time (20,000 years), which doesn't seem surprising.
DeleteThink we'll make it to 20,000 years?
DeleteSorry about the spam which showed up recently on several posts on PEOTS. That poster is now blocked.
Gee, I hope not; my 401(k) will run out long before that.
DeleteAs a species. . .
DeleteBut, ;-), jan.
I don't think climate change poses a serious threat to us as a species. It may shift areas of arable land and coastal real estate prices, governments may rise and fall, but we're pretty adaptable organisms.
DeleteThat's what one dinosaur said to the other. . .
Delete{JK, sort of}
Yeah, and dinosaurs are still around, or are we gonna have that argument about birds not being dinosaurs again? Anyway, the K-Pg event was even more sudden than the industrial revolution, and even though it sounds speciesist to say it, I think we're cleverer than dinosaurs.
DeleteMaybe. Probably, even.
Deletejan, I almost added a line about birds and dinosaurs but figured it was an argument for the birds ;-).
Earthquake advisory for parts of Southern California
ReplyDeleteSpeaking of threats to the planet...
ReplyDeleteIsn't it funny how certain words may evoke predictable, albeit incorrect, reactions? Thanks for sharing this, jan.
DeleteYou asked about switching from black tray to white tray: I can't say I have an instant equivalent, but in school they told us to take our drawings and rotate them 180 degrees, and take a look from the other side. Still a good idea.
ReplyDeleteeco, I agree, it's a great idea for any drawings.
DeleteI've also found it useful, on occasion, to read text upside-down.
¿ǝǝɹƃɐ noʎ plnoM
plnom I. Though that's dangerously close to one of those annoying Shortzian alarm clock puzzles.
DeleteI am reasonably adept at writing upside down, handy when sitting across a table from a client, and occasionally impresses them unduly. Easier for left-handed folk used to contorting their wrists to avoid smearing the ink, they just rotate their hands.
Here's an interesting little study on a simple step to address antibiotic misuse and resulting antibiotic resistance.
ReplyDeleteSome background: For the past couple of decades, a class of antibiotics known as fluoroquinolones, such as Cipro and Levaquin, has become very popular for treating many common infections, including urinary tract infections and pneumonia. As their use has increased, not only have serious side effects, like tendon ruptures, become more prevalent, but resistant bacteria have, predictably, become more common. But getting prescribers to change their habits can be difficult.
In this study, a hospital lab simply stopped reporting susceptibility to Cipro when a culture was ordered, as long as other effective antibiotics were identified. If a prescriber called the lab because none of the other antibiotics were appropriate for a given patient, susceptibility to Cipro was reported. The result? Not only did prescriptions for Cipro drop by more than half, but within a year resistance to Cipro also fell significantly. Pretty good outcome for such a cheap and easy intervention.
Fascinating! Very clever.
DeleteNew post on "How to Read Red Aspen Leaves: Anthocyanins and Sun Block for Leaves" is now up.
ReplyDeleteHappy anniversary! I'm late to the party, I know, but I'm catching up on posts I missed due to travel and family health issues. Thanks for the fascinating science, as always!
ReplyDelete