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Wednesday, September 28, 2016

Geological Society of America Meets in Denver: Paleocene-Eocene Thermal Warming and Comparisons to Today's Global Warming

      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.

     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?


Wednesday, September 21, 2016

Antikythera Mechanism Shipwreck Revisited: Human Skeleton Over 2,000 Years Old Discovered at Site

      Parts of a 2,000-plus-year-old skeleton have been recovered from the shipwreck which contained an early analog computer, the Antikythera Mechanism, which we discussed here at Partial Ellipsis of the Sun in 2014.

      Researchers found the skeleton last August during their ongoing excavation of the wreck, which lies on the ocean floor off the Greek island of Antikythera in the Aegean Sea.

      “Against all odds, the bones survived over 2,000 years at the bottom of the sea, and they appear to be in fairly good condition,” Dr. Hannes Schroeder, DNA expert, of the Natural History Museum in Copenhagen, Denmark, said.

     The discovery consists of a partial skull with three teeth, arm and leg bones, and several parts of ribs as reported yesterday in Nature. They are the first bones to be recovered from the wreck, particularly exciting during this era of DNA sequencing.

       The passenger or crew member “was trapped in the ship when it went down and he or she must have been buried very rapidly or the bones would have (been) gone by now.” Some of the bones remain on the seafloor, but others have been brought to the surface for analysis.

      If the research team, which is led by experts from Woods Hole, can recover DNA from the skeleton, they may be able to confirm the individual’s gender and hair and eye color, as well as his or her ethnicity and geographic origin.

      The wreck, which is believed to be of a Greek trading or cargo ship, is the largest ancient shipwreck ever discovered. Since its discovery by sponge divers in 1900, divers have recovered extraordinary artifacts including glassware, gold jewelry,

marble statues and an ancient weapon known as a "dolphin,"

a lead and iron artifact that weighs about 220 pounds. "Dolphins" were defensive weapons that were dropped from the ship’s yard, a spar on the mast, onto the deck of an attacking ship, such as a pirate vessel. 

      The Antikythera Mechanism remains the star of the seafloor find, at least so far.

       These are the best of (DNA) times. . .

Speaking of times, we are close to the 3-year anniversary of Partial Ellipsis of the Sun on October first!


Tuesday, September 13, 2016

Speaking of Geologic Time Periods Ending in E: Indian Fossils and the Spread of Primate-Like Animals: India's Island Days

      Well-preserved bones of rat-sized creatures excavated in an Indian coal mine may come from close relatives of the first primate-like animals, Iowa, USA, researchers describe.

     A set of two dozen limb fossils, dating to about 54.5 million years ago during the Eocene, raises India’s profile as a possible hotbed of early primate evolution, says biologist Dr. Rachel Dunn. 

      Bones from Vastan coal mine in Gujarat, India’s westernmost state, indicate that these small tree-dwellers resembled the first primates from as early as 65 million years ago, the scientists report in the October 2016 Journal of Human Evolution.

     These discoveries add to previously reported jaws, teeth and limb bones of four ancient primate species found in the same mine. “The Vastan primates probably approximate a common primate ancestor better than any fossils found previously,” says paleontologist and study co-author Dr. Kenneth Rose of Johns Hopkins University.

     The Vastan animals were about the size of living gray mouse lemurs and dwarf lemurs, weighing roughly 150 to 300 grams (about half a pound), the investigators estimate. 

      Most Vastan creatures possessed a basic climbing ability unlike the more specialized builds of members of the two ancient primate groups that gave rise to present-day primates, the researchers say. One of those groups, omomyids, consisted of relatives of tarsiers, monkeys and apes. 

       The other group, adapoids, included relatives of lemurs, lorises and bushbabies. The Indian primates were tree-dwellers but could not leap from branch to branch like lemurs or ascend trees with the slow-but-sure grips of lorises, the new report concludes.

      Vastan primates probably descended from a common ancestor of omomyids and adapoids, the researchers propose. India was a drifting landmass headed north toward a collision with mainland Asia when the Vastan primates were alive. Isolated on a huge chunk of land, the Indian primates evolved relatively slowly, retaining a great number of ancestral skeletal traits, the researchers propose.

      “It’s possible that India played an important role in primate evolution,” says evolutionary anthropologist Dr. Doug Boyer of Duke University. In 2010, a team led by Boyer reported that a roughly 65-million-year-old fossil found in southern India might be a close relative of the common ancestor of primates, tree shrews and flying lemurs (which glide rather than fly and are not true lemurs).

     One possibility is that primates and their close relatives evolved in isolation on the island continent of India between around 65 million and 55 million years ago, Dr. Boyer suggests. Primates then spread around the world once India joined Asia by about 50(?) million years ago.

     This is a controversial idea. An increasing number of scientists suspect primates originated in Asia. Chinese primate fossils dating to 56 million to 55 million years ago are slightly older than the Vastan primates. The Chinese finds show signs of having been omomyids.

      And in at least one respect, Dr. Boyer says, some of the new Vastan fossils may be more specialized than their discoverers claim. Vastan ankle bones, for instance, look enough like those of modern lemurs to raise doubts that the Indian primates were direct descendants of primate precursors.

      Dr. Dunn, however, regards the overall anatomy of the Vastan fossils as “the most direct evidence we have” that ancestors of early primates lacked lemurs’ leaping abilities, contrary to what some researchers have argued. 

Your thoughts? Omo or Ada? Or?

P.S. My oldest peach tree is loaded with fruit this year! They are just ripening now.

Wednesday, September 7, 2016

Quiescence: Not Just for Popsicles Any More; A Nicaraguan Volcano Goes Quiet Just Before Eruption

      Volcano semiotics indicating when a volcano is going to erupt include seismographs that display an increase in small tremors which might indicate that magma beneath the mountain is moving, a release of volcanic gases like sulfur dioxide and carbon dioxide, and changes in the physical shape of the volcano such as depressions or growths.

      While these clues tell researchers that the forces that fuel eruptions are moving, they don’t necessarily provide a timeline for when the eruptions will occur.

      By looking at the rate at which earthquakes happen in Nicaragua’s Telica Volcano, a team of scientists studying the volcano have discovered a new method of forecasting volcanic explosions. Their study, published this month in Earth and Planetary Science Letters, describes a period of seismic quiescence, or quiet time, that occurs immediately before an individual explosion.

      Volcanic eruptions are generally made up of many different explosions which can span hours, days, or even months. Depending on how much pressure has been building within the volcano, these individual explosions can range from small bursts of steam to giant, gaseous plumes of ash and smoke. Many smaller eruptions, those on the lower end of the Volcanic Explosivity Index (VEI), occur with little consequence to the people living in the region, while the larger explosions can have devastating effects on nearby communities.

      “We first realized the potential impact of our finding as the 2011 eruption of Telica was in progress and we started to understand that there was a pattern of precursory seismic quiescence prior to each explosion”, says Dr. Diana Roman, one of the study’s co-authors. “We were very excited about the forecasting potential of the quiescence at that time, but we had to do quite a lot more work after the eruption was over to understand the phenomenon and its relationship to the volcano's activity.” [One of the only other time I see the word quiescent is on "quiescently frozen popsicles."]

      Of the 50 explosions studied during Telica’s 2011 eruption, 48 of them were preceded by some sort of seismic silence.

      In addition, there appeared to be a correlation between the length of the quiet time and how catastrophic each explosion was. In short—the longer the quiet time, the more volatile each explosion was. Why does this happen?

     The team discovered that the pathways along which the volcanic gases escape become sealed, which builds pressure. The longer these gases spend trapped beneath the surface, the larger and more catastrophic the ensuing eruption is. The researchers suspect that newly formed minerals might block pathways inside the volcano, or possibly the pathways simply collapse, impeding avenues of escape for volcanic gases.

      Although each eruption is different, and so is each volcano, the implications of a study like this could be far-reaching.

      “I think there is great potential for our findings to be used in a real-time monitoring context,” Dr. Roman says, “the quiescence signal is relatively easy to detect as it requires only one seismometer rather than a large network of seismometers, meaning it can be implemented more cheaply.”

The closer scientists get to predicting volcanic eruptions, the more easily people can learn to live along the flanks of volcanoes such as Telica.


Quiescently unfrozen in the Rocky Mountains,