The Earth Story

Impact

This is a complicated figure from a recently published paper featuring a really neat geologic site. This is an outcrop of the debris from the asteroid impact at the end of South America after the impact.

Start with the map in the upper right. The map shows the modern day locations of the Chicxulub impact crater on the Yucatan Peninsula and the tiny island of Gorgonilla off the coast of Colombia, where this outcrop was found.

The vertical column at the far left shows the sedimentary sequence. These rocks are off the coast of South America, near the Andes Mountains today. 65 million years ago, there were volcanoes nearby just like we find along this coastline today. This sequence of rocks therefore includes a basaltic lava flow and tuffs that have mixed with sediments. Tuffs are ash that exploded out of volcanoes, so volcanoes were feeding this site and the type of sediment deposited was alternating between sandy and muddy.

Then, right in the middle of this sequence, a whole bunch of spheres of glass appear. These are debris from the impact itself and they’re shown at the top in the figure labeled A. When the asteroid hit the Yucatan Peninsula, it vaporized and melted some of the target rocks. That molten rock splashed out of the crater like water bursting from a balloon and it rained down around the entire surrounding area. It cooled off rapidly as it flew through the air, creating spheres of hot glass that pelted the landscape. That spherule layer is the direct debris of the impact.

The final 2 frames show what has happened to the other sedimentary layers. The spherule layer is colored green in the center image – note that it’s a little bit bent. The zoomed in image below it shows that the once simple sedimentary beds have been bent and disturbed. When the impact took place, it caused geologic disruption throughout the entire region. It is thought that earthquakes continued shaking the land for tens of minutes after the impact, long enough for blast debris to rain down and still be disrupted. These bent sedimentary layers were shaken up by the energy released after the initial blast.

The scientists at this site characterized pollen samples in the sediments before and after the impact to analyze the types of plants living in these areas. They found that the plant populations shifted dramatically after the impact and one group of ferns that has been thought to occupy areas that are hit with disasters shows up just after the impact layer.

-JBB

Image credit and original paper: https://bit.ly/2rGLjqn

Shocked

This researcher is using a petrographic microscope to examine a mineral grain recovered from the just-completed effort to core and sample the rim of the crater generated during the Chicxulub Impact on the shores of what is today the Yucatan Peninsula (https://tmblr.co/Zyv2Js237-vel). The monitor shows the grain being seen under the microscope and also adds a scalebar.

The projected image is a grain of very fine sand only a hundred or so micrometers across. You’re actually looking at a bit of a sand grain that was shocked during the impact that killed the dinosaurs and was recovered from that drill core.

When an asteroid impacts a planet, part of the energy of that impact is converted into a shock wave. That wave propagates outwards through everything, distorting the atomic structures of every mineral grain it travels through. As the wave passes, first atoms are squeezed together, then they move back apart after the wave releases.

Shock waves can do lots of damage as they pass through a mineral. Some minerals can take the stress, but others fracture and some even completely melt. The mineral quartz responds to shock by producing “planar deformation features” – basically specific planes in the mineral have been kinked or broken, creating features that can be seen under a microscope.

The pattern of lines defined by the dark dots running from the upper left to the lower right of this grain establishes that it is a bit of shocked quartz (https://t.co/1N6HchliLV), a relic of the Chicxulub impact. The initial coring of this site is now complete and 1300 meters of core through the ring of the crater have been collected. They will now be taken back to facilities in the US and Germany where they will be opened and characterized.

-JBB

Image credit: Max Alexander/B612/Asteroid Day/BBC http://www.bbc.com/news/science-environment-36377679

Reference: http://bit.ly/1Z0rliw

The cenotes of Yucatán

The Yucatán peninsula in Mexico is famous for its cenotes, which historically have been linked to the Maya practice of human sacrifice. A sinkhole or cenote forms when sections of a cave roof collapse leaving a vertical shaft and exposing the underlying cave or cave system. Often, but not always the cenotes fill with rainwater. The word cenote derived from the Yukatec Maya... word ts’onot, which refers to available groundwater. Cenotes can be very deep (the deepest water-filled being El Zacatón cenote in Mexico with 339m).

On the Yucatán peninsula cenotes are the only sources of water (few lakes and rivers are found in the area), thus they were of utter importance for the Maya to survive. In Mayan cosmology, caves, sinkholes and water fountains were related to fertility and the world of the dead. They were seen as access points or symbolic steps to underworld, Xibalba, in which a variety of mythological beings lived.

The practice of human sacrifice among the ancient Maya is evident from scenes of decapitation and heart excision on mural paintings, vessels, and bass-relief sculptures as well as from colonial accounts. An account by Don Diego Quijada actually mentions that victims of human sacrifice were disposed of in cenotes or wells or caves. A source of Fray Diego de Landa speaks of human sacrifices victims being thrown in the cenote alive. Body mutilation could also take place post-mortem. In addition, accounts state that either outcasts, individuals from outside society, slaves, orphans or criminals were picked to be sacrificed.

So, how many human remains were found in these cenotes? The Las Calaveras cenote near Punta Laguna contained the skeletal remains of 118 individuals. (The name calavera is Spanish for skull) The San Antonio cenote near Merida contained at least 28 individuals, as well as colonial pottery and animal bones. In addition, the X-Coton, Xlacah, Canun, Naharon and the Holtun and Sacred cenote at Chichen Itza contained human remains. However, it is not evident that all these were sacrificial victims. There is no dominance of a certain sex. Woman, men and children appear in similar manners. Some skeletons are clearly intentionally placed and show no sign of being sacrificed. Thus cenotes could have also been aquatic burial places. Other skeletons, as the one found in the Holtun cenote, do show signs of having died a violent death.

So why does the Yucatan have so many cenotes? The answer remarkably has to do with the 180 km diameter Chicxulub impact crater, that is buried 900 m under the north- western tip of the peninsula. A so-called necklace of sinkholes lies on the rim of the impact crater. Most likely the cenotes were created by fractures in the rim as an aftereffect of the meteorite impact. (see: http://www.jpl.nasa.gov/news/news.php?feature=8)

-- BO

Picture: http://bit.ly/14gWxCd. The Ik Kil cenote near Chichen Itza. It is unclear if any human remains were found in here.

References and further reading:

http://www.nationalgeographic.com/explorers/ancient-maya-cave-exploration-photos/

http://news.nationalgeographic.com/news/2011/07/pictures/110706-human-sacrifice-bones-maya-chichen-itza-ancient-science-mexico-cenote/

http://www.jpl.nasa.gov/news/news.php?feature=8

Leshikar-Denton M.E. & Pilar Luna Erreguerena. 2008. Underwater and Maritime Archaeology in Latin America and the Caribbean. Left Coast Press Inc.

Serafin, Stanley and Calos Peraza Lope. 2007. New Perspectives on Human Sacrifice and Ritual Body Treatments in Ancient Maya Society Interdisciplinary Contributions to Archaeology 2007, pp 232-250.

DINOSAUR EXTINCTION CAUSED BY COMET, NEW RESEARCH SUGGESTS

In recent history there has been a general consensus that between 65 and 66 million years ago an enormous asteroid made fall on planet Earth. After the asteroid’s initial impact, an enormous cloud of dust was sent up into the atmosphere, blocking out most sunlight and in turn killing most plant life and dinosaurs. The crash site, Chicxulub Crater, is located on the Yucatan Peninsula and covers an area of about 25,450 km2 (9,826 miles2). Despite some scientists who believe that the extinction was caused by ongoing volcanic eruptions in Deccan Traps in India, recent evidence has concluded that whatever caused the Chicxulub Crater also caused the wipeout of the dinosaurs.

All of this has held true until a recent study carried out by two Dartmouth University researchers which strongly suggests that the impact on the Yucatan Peninsula was caused by a comet, rather than an asteroid. Professor Jason Moore and Mukul Sharma of the Department of Earth Sciences took a different route than other scientists in executing their research. Since unusually high iridium traces in and nearby the Chicxulub Crater would suggest an impact by an asteroid, most scientists have agreed that that was the cause of the dinosaurs’ extinction. However Professor Moore and Sharma attributed these unusually high levels of iridium to incorrect documentation and natural occurrences such as preferential concentration on the ocean floor.

After dismissing a lot of the excess iridium that has been detected in and around the impact zone, the two professors’ findings were quite interesting. They observed the levels of osmium, another element that was delivered from the object’s impact. The resulting data suggests that the impact generated far less debris than previously anticipated. Their research also suggests that the impact was one of a much smaller object and at a much higher velocity. Such qualifications are met by comets.

The two professors’ research has had both positive and negative feedback from the public. If anything, it will gear some more research into other directions differing from the asteroid theory. In the process, we are bound to make new discoveries about the Chicxulub Crater and the great extinction of the dinosaurs.

--Pete D

Image Credit: Julian Baum / Science Photo Library http://www.sciencephoto.com/media/172395/enlarge

References: 1. http://www.sciencedaily.com/releases/2013/04/130404122409.htm 2. http://www.huffingtonpost.com/2013/03/23/asteroid-killed-dinosaurs-comet-extinction_n_2937296.html 3. http://news.bbc.co.uk/2/hi/science/nature/8550504.stm

There are still many scientists that believe an asteroid or comet (bit.ly/1XdMXqq), estimated at about 6 miles (10 kilometers) across, was to blame for the wipe out of the dinosaurs. Buried underneath the Yucatan Peninsula in Mexico, the Chicxulub (pronounced CHEEK-she-loob) crater is estimated to have created an initial hole 60 miles (100km) wide and more than 18 miles (30km) deep before collapsing to form a final crater more than 110 miles (180 km) wide and 12 miles (20 km) in depth.

Recently this theory has been challenged by more evidence researchers have been uncovering. A group of scientists led by Prof Gerta Keller of Princeton and Prof Wolfgang Stinnesbeck of the University of Karlsruhe found a series of geological clues in the rock formations where the iridium layer (bit.ly/1w9erCF) was separated from the spherule layer (bit.ly/1M9ymq0) by many meters of sandstone. They also found evidence of ancient worm borrows. In conclusion, the team theorize there must be a gap of some 300,000 years between the deposition of the spherules (from the crater) and the iridium (from the impact). The Chicxulub impact was too old therefore there had to have been two different impacts. That other crater has yet to be discovered.

In April, a $10 million drilling project will be constructed, sponsored by the International Ocean Discovery Program (IODP) and the International Continental Scientific Drilling Program, offshores in the Gulf of Mexico. Scientists and researchers will try to sink a diamond-tipped bit into the very center of this crater and retrieve rock cores that they hope will contain clues to novel microbial life and how ecosystems come back after such a tragedy. They also plan to drill into a circular ridge around the center of the crater's rim, called a "peak ring," to gain more information on how they form.

There are only two craters confirmed larger than Chicxulub that should also have peak rings: the 2-billion-year-old Vredefort crater in South Africa, and the 1.8-billion-year-old Sudbury crater in Canada. However, as University of Texas, Austin Sean Gulick, geophysicist and co-chief of this project says “Chicxulub is the only preserved structure with an intact peak ring that we can get to, all the other ones are either on another planet or they’ve been eroded.”

Although this is the first attempt at an offshore drilling, in the 1950s geologists for Pemex (Mexico’s national oil company) drilled several exploratory wells then lost interest when they found volcanic rocks instead of oil-bearing sediments. Then in 1991, Alan Hildebrand, a geologist at the University of Calgary in Canada, found quartz crystals shocked by an impact in the Pemex well core samples that had been sitting around for more than a decade. In 2005, a remote-sensing campaign, led by co–chief scientist Joanna Morgan of Imperial College London and Gulick, used small seismic explosions to illuminate the subterranean structures and pinpoint the best spot to reach the peak ring.

The researchers now are interested not only in the structure of the peak ring rocks but also what life they might host. Remote sensing has already suggested that the peak ring is less dense than expected for a granite - a sign that the rocks are porous and fractured in places. It is possible that these fractures, in the wake of the impact, were filled with hot fluids. They will count and culture any microbes found living in the fractures, and sequence their DNA. They could find genes showing that descendants of those that lived after the impact derive their energy not from carbon and oxygen, like most microbes, but from iron or sulfur deposited by the hot fluids percolating through the fractured rock.

--Mi

Image Credit: bit.ly/1pzHiAo Sources: bit.ly/1U4hGIv bit.ly/1TW92KO

Drilling the Chicxulub

Drilling platforms are not an unusual sight in the Gulf of Mexico (which is rich in oil and natural gas deposits), but the rig to be put in place at the end of this month will be drilling for information.

Halfway on top of the Yucatan Peninsula and halfway under the Gulf lays the Chicxulub impact crater (pronounced cheek’ she lube). Measuring 177 km (110 mi) in diameter, the crater is thought to have resulted from the impact of an object approximately 10 km (6 mi) in diameter striking the planet more than 66 million years ago. Linked with global occurrences of tektites (spheres of glassy material), shocked quartz, and a layer of the rare element iridium, the Chicxulub impact event is thought by many to have been the cause of the K-T (Cretaceous-Tertiary) mass extinction.

The most notable physical features of the crater are a ring of cenotes (water-filled sink holes which were once used in Mayan ceremonies) around its land-based rim and gravitational anomalies appearing on magnetic survey maps of the Gulf. The $10 million project is sponsored by the International Ocean Discovery Program (IODP) and the International Continental Scientific Drilling Program. The team will attempt to sink a diamond-tipped bit into the intact peak ring of the impact crater.

Thirty km (19 mi) offshore of the Mexican port of Progreso, the specially equipped vessel will sink three pylons in water 17 m (56 ft) deep and raise itself above the surface of the Gulf. Drilling is planned to begin in early April and continue for 2 months, passing through 500 m (1640 ft) of limestone to extract core samples, and allowing scientists to look for changes in rock types, catalog microfossils, and collect DNA samples. CW

Image

http://bit.ly/1TW92KO

Sources

http://bit.ly/1TW92KO

http://bit.ly/1LHxkXC

http://www.ucmp.berkeley.edu/education/events/cowen1b.html

http://neo.jpl.nasa.gov/images/yucatan.html

http://www.lpi.usra.edu/science/kring/epo_web/news/chicxulub1.html

http://minerals.cr.usgs.gov/gips/na/space.html

http://www.atlasobscura.com/places/chicxulub-crater

What do geologists do when you give them big computers? Here’s a simulation of the Chicxulub impact and time immediately following it, showing the cone of debris and the development of the crater.

Burning Sky

A new University of Colorado Boulder study sheds new light on the conditions after a Manhattan-sized asteroid hit Mexico 66 million years ago (and spelled the doom for dinosaurs).

The research team used models that show the collision would have vaporized huge amounts of rock that then blew high above Earth’s atmosphere. An afterwards firestorm of re-entering material would have heated the upper atmosphere for hours at 1,480 degrees Celsius (2,700 degrees Fahrenheit). Every living thing not underground or underwater would have died.

The CU-led team developed a different explanation for the little amounts of charcoal found at the Cretaceous-Paleogene(or K-Pg) boundary, dating to 66 million years ago, when the asteroid struck Earth, and firestorms began. The researchers found that similar studies had corrected their data for changing sedimentation rates. When they did the same for the charcoal data, they actually showed that there was an excess of charcoal, not a deficiency.

“Our data show the conditions back then are consistent with widespread fires across the planet," said Robertson, a research scientist, “meaning 100% extinction rates for about 80% of all life on Earth”.

After the asteroid impact, the vaporized rock condensed into sand-grain-sized spheres rising above the atmosphere. As the material re-entered the atmosphere, it would have heated enough the upper atmosphere to trigger an infrared “heat-pulse” so hot to turn the sky to glow red for hours. The radiation from the upper atmosphere reaching Earth’s surface was enough to mean trouble for anyone on the surface igniting tinder, dead leaves and pine needles.

“It’s likely that the total amount of infrared heat was equal to 1 megaton bomb exploding every four miles over the entire Earth”, said Robertson.

The paper published this week on the Journal of Geophysical Research-Biogeosciences: http://bit.ly/YlfDm9

-CHD

Source: http://www.colorado.edu/news/releases/2013/03/27/cu-study-provides-new-evidence-ancient-asteroid-caused-global-firestorm Image credit: Don Davis

Asteroids versus flood basalts: The debate continues

Ever since the discovery of a worldwide layer of iridium rich rocks at the marker layer for the mass extinction that killed off the dinosaurs (except birds of course) and ammonites, followed by the recognition of Chixulub crater and widespread tsunami and fire deposits as the telltale proof of asteroid impact, a debate has raged over whether it was the sole cause of extinction. Many scientists have a second culprit in mind: the vast outpourings of basalt that flowed out over large swathes of what is now India at the same time.

Much discussion has surrounded various 'kill mechanisms' for both sources, and most balanced scientists recognise that both contributed to a perfect storm for life on Earth, with both events stressing ecosystems towards extinction. The climate change and ocean acidification of the volcanic gases combined with several dark years (as smoke blocked out the sunlight) seem to have combined to make existence very difficult for a wide variety of organisms.

A new study published in Science based on more precise dating of the Deccan Trapps (as the basalts are known) implies that the impact may have triggered the largest eruptions in the million year long sequence, in which most of the lava (and volcanic gases) emerged from the planet's depths. The high precision argon isotope data shows that the lava emerged within 50,000 years of impact and that the extinction was simultaneous, a figure smaller than the margin of error on the measurements, so it may have been a matter of days or months for all we know.

They suspect that the shockwave of the impact shook the world's volcanic plumbing systems, possibly opening up a way for magma that had been stalled in the crust and might never have erupted to explode outwards for many thousands of years. These eruptions would have made it much harder for ecosystems to recover, leading to further extinctions, and making the consequences of impact on life much worse that they would have been without them. It took a full half million years for the environment to start recovering.

The eruption rate doubled after impact, and a semi continuous event became punctuated, with long gaps between eruptions, stringing out the period of environmental stress. The team thinks the impact somehow made the lava chambers bigger, and it has been argued before (on contested evidence) that the Deccan Plateau occupied the antipodes of the impact site and had its force focussed around the crust into it, possibly causing a megaquake to release the pent up magma. While the causal link remains unclear, the correlation of the three events in time is increasingly hard to dispute. Further research to refine our understanding of the chronology of the Deccan eruptions is ongoing, and we will report as events warrant.

Loz

Image credit: Mopic/Alamy Trapps: Mike Widdowson/GSA Trex: David Monniaux http://bit.ly/1Q82HrQ http://bit.ly/1Q5J17S Original paper, paywall access: http://bit.ly/1VwWM0T

An A-Z of Extinction (part 4/4: S-Z)

As we enter what has now been termed the 6th mass extinction on Earth, I thought we could take a closer look at the process and causes of extinctions, as well as the species that have suffered. Do you know your ABCs?

S is for Sumatran Elephant. The Sumatran Forest is becoming used more and more for agricultural purposes; providing toilet paper, vegetable oil and biofuel globally. Since 2010, more than half of the Sumatran Rainforest has been felled. Unfortunately, this is the habitat of the Sumatran elephant, which are increasingly facing the loss of their habitats. Conservationists working with the Sumatran elephants believe that if this rate of deforestation is not slowed, these elephants could become extinct by 2025.

T is for Tiger. Tigers have been believed magical, and their body parts (particularly their bones, eyes, whiskers and teeth) have been used in Chinese medicines for generations. This has led to a lucrative trade in which killing tigers is and was exceedingly profitable for their poachers. As many of this poaching occurs illegally, enforcement of laws and sanctions against tiger hunting by the Chinese government is necessary to prevent the extinction of tigers in the wild. For example, the South China Tiger is considered ‘functionally extinct’ and has not been sighted in the wild in 25 years.

V is for Verhoeven’s Giant Tree Rat. Verhoeven’s Giant Tree Rat was named after the Dutch priest Father Theodor Verhoeven famed for his discovery of fossils from dwarf elephants. The rat lived in Flores, Indonesia and has been estimated to have become extinct in 1500 AD.

W is for Wolf. The Falkland Islands Wolf was the only native mammal on the Falkland Islands that is believed to have eaten ground-nesting birds. However, when the first settlers came to the island they believed the wolf would hunt their sheep and thus shot the wolves; leading to their extinction in 1876. This makes the Falkland Islands Wolf the first canid to become extinct in historical times.

(e)X is for Extinction. You didn't think I’d actually find a genuine x, did you? Extinction is the termination of a species, marked by the death of the last individual member of the species.

Y is for Yucatán Peninsula. The Yucatán Peninsula hosts the Chicxulub Crater, a multi-ringed impact crater 180km in diameter. On dating the crater, scientists noted that it coincides with the Cretaceous –Paleogene boundary and mass extinction. This end-Cretaceous Extinction occurred over 66 million years and led to the extinction of 75% of species.

Z is for New Zealand Greater Short-Tailed Bat. The New Zealand Greater Short-Tailed Bat had been presumed extinct following no confirmations of sightings of it since 1967 on either of the islands. It is believed that the bat was partly carnivorous (eating nesting birds) and spent much of its time on the ground.

~SA

Image: http://bit.ly/1NFSDEW South China Tiger by Save China’s Tiger

Part 1: http://on.fb.me/1GSV2dp Part 2: http://on.fb.me/1BQUOod Part 3: http://on.fb.me/1CdK57j

New timing data for the K-Pg boundary event.

Teams from the Berkeley Geochronology Center (BGC), the University of California, Berkeley, and universities in the Netherlands and the United Kingdom, have come up with new evidence that the most famous of all the extinction events, because it wiped out the dinosaurs, the K-Pg extinction was caused by an asteroid impact; or at least the final stage of the extinction event was accompanied by an impact.

The research team had noticed that none of the existing dates seemed to match, and the method used wasn't as accurate as it could be, so before attempting to date the impact they re-calibrated and revamped the existing 40Ar/39Ar dating technique.

Using ash collected from the Hell Creek Formation in Montana and tektites from Haiti, the researchers have come up with the most precise date yet for the impact event, 66,038,000ma.

This date is, according to the team, accurate to within 11k years, and is the most precise date yet.

The team are quick to add that whilst there was an impact event accompanying the final stage of the K-Pg event, there was a decline in flora and fauna for over a million years before the impact. Climate variation, possibly from erupting flood basalt's (the Deccan traps) had caused dramatic changes in environmental conditions, leading to biological decline.

The team are also keen to date the Deccan Traps, and it is expected that the new dates will be gathered in the near future.

-LL

Links; http://www.sciencedaily.com/releases/2013/02/130207141444.htm

http://www.sciencemag.org/content/339/6120/684

Image; Artists impression of an asteroid impacting the Earth. revers_jr / Fotolia

Digging into Chicxulub Crater

In the 20 years since the 250-km wide Chicxulub Crater was discovered in Mexican Yucatan Peninsula, scientists have debated heavily about its origins and implications. However, some of the debate eventually reached some form of consensus. The impact likely caused a catastrophic mass extinction event that wiped out the dinosaur population 65 million years ago, a point in geologic time known as the Cretaceous-Tertiary boundary, or K-T boundary. But another major question remains — was this impact an isolated event, or was it a part of a series of collisions that drastically changed global climate and eventually led to the dinosaurs’ demise?

Part of this lingering question could be answered by a team of international scientists who are planning an ambitious drilling project to obtain a 1,500m-deep core from the center of the crater. As part of the crater is underwater, scientists used subsurface images to determine a sampling location near the crater’s peak ring, which are to the steep ridges that encircle the crater. The ring formed from the outward-facing blast of rock material when impact occurred — much like the circular crests that form when a rock is thrown into pond. No samples have ever been obtained from the peak ring, which scientists believe contains material that blasted outwards from the point of impact.

Scientists have simulated various models to describe the impact, none of which have been tested. Using a core that could go back 15 million years in time may give them greater insight into the mechanics and extent of one of the most devastating events in earth history.

-DC

Photo credit: http://bit.ly/1CBcE9m

http://bit.ly/1CHCG9H

Our previous write-ups on Chicxulub Crater: http://tinyurl.com/kwyg5r9

http://on.fb.me/1JDAQgf

Other references: http://bit.ly/1cbTQap

http://bit.ly/1GDnYIF

http://bit.ly/1iVanPq

http://bit.ly/1NygaMi

http://bit.ly/1CK9XkO

Did a mega volcano kill the dinosaurs? The Cretaceous-Paleogene/Tertiary extinction event (K-Pg or K-T as it is known by geologists) was previously thought to be the only mass extinction out of the “big five” not attributable to volcanism. Instead, the currently accepted theory linked a meteorite impact near present-day Chicxulub, Mexico as the lone cause (known as the Alvarez hypothesis), although there is growing support for volcanic activity as a second major factor. Now, new research led by Brian Schoene of Princeton University has added further evidence that non-avian dinosaurs were actually wiped out by volcanism rather than a meteorite collision some 66 million years ago, confirming what some geoscientists, such as Dewey McLean, long suspected. The Deccan Traps, a massive flood basalt in India, has long been known as a series of volcanic events that occurred at around the time of extinction, but the majority believed that they erupted too early on to have had a significant effect. Scientists have now tightened the timeline of the main sequence of eruptions, which now appear to have happened very soon before - geologically speaking - the extinction, with new precision rock dating evidence (using U-Pb dating in zircons) showing that the main phase of eruptions occurred within 250,000 years of extinction, rather than millions. This new timeline is very important, as the volcanic gases now believed to be responsible for dramatic, extinction-inducing climate change (particularly sulfur dioxide) would have been released very shortly before, and during (up to 750,000 years) the time of the K-Pg extinction. It adds weight to the idea that volcanism was the primary cause of extinction, with the meteor impact as the icing on the cake. During it's active phase, the Deccan Traps volcano released over 1.1 million km3 (264,000 cu mi) of lava, with layer upon layer of basalt culminating in a depth of 2,000 m (6,562 ft) thick. Since then, it has gradually been eroded down to 512,000 km3 (123,000 cu mi). Scientists are now working on further constraining the timing of eruptions and using this data to refine computer-based environmental change models. This will enable researchers to better determine the individual as well as cumulative effects of Deccan Traps volcanism and Chicxulub meteorite impact on Earth. - YK Past articles: Deccan Traps: http://on.fb.me/1ByYtnX & http://on.fb.me/1ByYtnX Did a comet cause extinction?: http://on.fb.me/14FWelu K-Pg event: http://on.fb.me/1xuvbk5 & http://on.fb.me/1uaQff9 end-Permian extinction event - http://tmblr.co/Zyv2Js18raAV1 Image credit: by Nichalp, 2007 (http://bit.ly/1B8kHyg) Used under CC licensing. Further reading: Deccan Traps - http://bit.ly/1BcXWcx & http://bit.ly/1sHvLzn Did the Traps wipe out the dinosaurs? http://bit.ly/1G4hEKz & http://bit.ly/17QFBWo Original paper by Schone et. al. - http://bit.ly/1C66iS8 (paywalled)

FIRE IN THE SKY On Friday, Feb 15 of 2013 a meteor exploded above the city of Chelyabinsk, Russia. The object was video taped tracing a fiery trail across the sky before erupting in a fireball so bright and powerful it lit up the sky similar to a nuclear blast, damaged hundreds of buildings, and injured up to an estimated 1100 individuals, mostly from flying glass from shattering windows. Refined measurements of the object place it at around 17 meters in diameter, and about 10,000 tons. The force of the blast is estimated at almost 500 kilotons; by comparison, the Fat Man and Little Boy bombs dropped on Japan in WWII only had a combined 37-kiloton yield. The blast was so powerful the USGS was able to detect it on their seismometers as far away as Golden, CO. At 7:17am local time on June 30, 1908, another meteor exploded over the forests of Tunguska, Siberia. This one exploded with about 15,000 kilotons. The Tunguska explosion was measured via seismic vibrations from 100km away, heard as a “deafening bang” with a fiery cloud on the horizon at 500km, and seen as a brilliant, sun-like fireball accompanied by a thunderous, deafening noise as far away as 170 km, and people as far away as 60km were knocked down and rendered unconscious. The closest people to that blast were reindeer herders approximately 30km from the blast; some were blown into the air and knocked unconscious, and one was thrown into a tree, later dying from his injuries. It also flattened more than 80 million trees over a 2,150 square km area and evidence points to a 1m fragment impacting the surface and creating a nearby lake. Approximately 65 million years ago, an asteroid estimated to be at least 10km wide impacted what is now the Yucatan Peninsula in Mexico. It left the Chicxulub Crater—one of the largest impact craters on the planet at almost 180km in diameter and 10km deep. The force of the impact itself is estimated to be at almost 100 billion kilotons. All life within 100km of the blast would have been exterminated immediately, with material being blasted into the atmosphere blotting out the sunlight and reducing temperatures around the globe. Without sunlight, plants died, leading to the starvation of herbivores, and eventually carnivores. Ultimately, almost 70% of all life on the planet was wiped out, including the dinosaurs. American lawmaker Rep. Dana Rohrabacher is using the latest explosion to highlight the need for a method of dealing with threats from space. The US has been spending millions of dollars on locating and tracking objects, but the one over Russia was so small that “…we aren’t even looking for objects of this size.” He went on to state ““What concerns me even more, however, is the fact that we have no plan that can protect the Earth from any comet or asteroid…so, even if we find one that will hit us, we might not be able to deflect it…This is the only preventable natural disaster, and we have mounting evidence that this a real and tangible danger." The US House science committee held hearings on the danger of meteorite impacts a few weeks after this event. When one scientist was asked what people should do if it was discovered a meteor was heading towards Earth...his answer was "pray". NASA already does have a program in place to attempt to detect Near-Earth Objects. The Near-Earth Object Program office at Nasa's Jet Propulsion Laboratory in Pasadena, CA has several projects in place and coordinates NASA's satellite network with others around the world to try and identify any objects that would approach Earth with the potential to cause damage. "We would expect an event of this magnitude to occur once every 100 years on average," said Paul Chodas of NASA's Near-Earth Object Program Office at the Jet Propulsion Laboratory in Pasadena, Calif. "When you have a fireball of this size we would expect a large number of meteorites to reach the surface and in this case there were probably some large ones." Additionally, the ESA is also working on this problem. Their Space Situational Awareness—SSA—program is dedicated to locating objects that pass near Earth and are large enough to do damage if they enter the atmosphere. “Today’s event is a strong reminder of why we need continuous efforts to survey and identify near-Earth objects,” said Thomas Reiter, ESA’s Director of Human Spaceflight and Operations. Specifically, the goal is to be able to locate and track objects larger than 40m at least three weeks before their closest approach to Earth. The SSA conducts sky searches using the ESA’s Optical Ground Station in Tenerife, Spain, as well as partnering with existing European and international asteroid survey activities. To achieve their goals, the ESA and partnering industries and agencies are developing a system of 1m diameter telescopes capable of imaging the entire sky in one night. -JW The image below is an artist's impression of the few days after the impact 65 million years ago (Picture courtesy of NASA) For more coverage of the Russian impact from The Universe and our sister page The Earth Story, check out http://on.fb.me/XjGCdq; http://on.fb.me/XfvVvq The seismic impact of the meteor: http://on.fb.me/XIi0dx A possible impact in a frozen lake by a meteorite fragment: http://on.fb.me/XjGwCu For more information, go to: http://neo.jpl.nasa.gov/index.html http://www.esa.int/Our_Activities/Operations/Russian_asteroid_strike http://www.jpl.nasa.gov/news/news.php?release=2013-061 http://www.space.com/19833-russia-meteor-asteroid-threat.html http://www.nbcbayarea.com/news/local/Fireball-Streaks-Across-Bay-Area-Sky-191503601.html http://www.universetoday.com/37487/tunguska-event/ http://nuclearweaponarchive.org/Usa/Med/Lbfm.html http://earthquake.usgs.gov/earthquakes/eventpage/usc000f7rz#summary