According to a recent study on ancient volcanism, dinosaurs flourished after ice rather than fire.
Massive volcanic eruptions that tore apart Pangaea, a large continent that at the time included nearly all of the planet's territory, occurred at the same time as the wipeout.
Over the course of some 600,000 years, millions of cubic miles of lava erupted, dividing what are today North Africa, Europe, and the Americas.
It signaled the end of the Triassic and the start of the Jurassic, when dinosaurs descended to rule the earth and replace Triassic animals.
It signaled the end of the Triassic and the start of the Jurassic, when dinosaurs descended to rule the earth and replace Triassic animals.
Although there has been much discussion over the precise causes of the End Triassic Extinction, the most prominent ones are that the carbon dioxide released by the eruptions accumulated over many millennia, bringing temperatures to levels that were unsupportable for many animals and acidifying the oceans.
However, a recent study finds that the primary cause was cold rather than warmth. The work provides evidence that the first lava pulses that terminated the Triassic were spectacular events that lasted less than a century each, rather than hundreds of thousands of years. The journal Proceedings of the National Academy of Sciences published the work.
However, a recent study finds that the primary cause was cold rather than warmth. The work provides evidence that the first lava pulses that terminated the Triassic were spectacular events that lasted less than a century each, rather than hundreds of thousands of years. The journal Proceedings of the National Academy of Sciences published the work.
Sunlight-reflecting sulfate particles were hurled into the sky during this shortened period, chilling the planet and freezing many of its people. According to the researchers, volcanic winters caused the most harm, but gradually increasing temperatures in an already hot environment—atmospheric carbon dioxide in the late Triassic was already three times that of today—may have completed the job later.
"Carbon dioxide and sulfates act not just in opposite ways, but opposite time frames," stated Dennis Kent, the lead author from the Lamont-Doherty Earth Observatory at the Columbia Climate School. "Sulfates have an almost immediate effect, whereas carbon dioxide takes a long time to accumulate and heat things. It takes us into the sphere of human comprehension. These incidents took place throughout the course of a lifetime.
Kent and colleagues in a pioneering 2013 study. Paleomagnetism researcher Kent found a consistent polarity reversal in strata immediately below the first CAMP eruptions, indicating that they all occurred simultaneously in what are now widely distributed regions of the earth.
The beginning of volcanism was then dated by colleagues using radioactive isotopes to 201,564,000 years ago, give or take a few tens of thousands of years. Many people believed that the enormous CAMP deposits must have taken many millennia to accumulate, even if scientists were unable to determine the size of the initial eruptions.
The beginning of volcanism was then dated by colleagues using radioactive isotopes to 201,564,000 years ago, give or take a few tens of thousands of years. Many people believed that the enormous CAMP deposits must have taken many millennia to accumulate, even if scientists were unable to determine the size of the initial eruptions.
In the latest study, Kent and associates correlated data from CAMP deposits in the Newark Basin of latest Jersey, along the Bay of Fundy in Nova Scotia, and in the Moroccan mountains. The alignments of magnetic particles in the rocks, which documented the previous movement of the Earth's magnetic pole during the eruptions, were their main piece of evidence.
This pole is displaced from the planet's constant axis of rotation, or true north, by a complicated series of events, and it also shifts by a few tenths of a degree annually. (The explanation for why compasses don't always point north.)
This pole is displaced from the planet's constant axis of rotation, or true north, by a complicated series of events, and it also shifts by a few tenths of a degree annually. (The explanation for why compasses don't always point north.)
As a result of this phenomena, magnetic particles in lava will all point in the same direction if they were deposited within a few decades of one another, but they will point 20 or 30 degrees differently if they were deposited, say, thousands of years later.
Five consecutive initial CAMP lava pulses, spaced out across roughly 40,000 years, were discovered by the researchers. Each of these pulses had magnetic particles oriented in a single direction, suggesting that the lava pulse had formed less than 100 years before drift of the magnetic pole could show up.
Five consecutive initial CAMP lava pulses, spaced out across roughly 40,000 years, were discovered by the researchers. Each of these pulses had magnetic particles oriented in a single direction, suggesting that the lava pulse had formed less than 100 years before drift of the magnetic pole could show up.
Temperatures are said to have plummeted as a result of these massive eruptions releasing so many sulfates so rapidly that the sun was mainly obscured. The ensuing cold spells are short-lived because volcanic sulfate aerosols tend to rain out of the atmosphere within years, unlike carbon dioxide, which lingers for eons. However, these volcanic winters were catastrophic because of the scale and speed of the eruptions.
Only the first CAMP pulses were hundreds of times larger, according to the researchers, who compared the CAMP series to sulfates from the Laki volcano eruption in Iceland in 1783, which resulted in extensive crop failures.
Only the first CAMP pulses were hundreds of times larger, according to the researchers, who compared the CAMP series to sulfates from the Laki volcano eruption in Iceland in 1783, which resulted in extensive crop failures.
Triassic-era fossils can be found in sediments just beneath the CAMP layers. These fossils include huge, flat-headed amphibians, bizarre tree lizards, large terrestrial and semiaquatic relatives of crocodiles, and numerous tropical plants. The CAMP eruptions then cause them to vanish.
Due to their small size and ability to live in burrows, little feathered dinosaurs, turtles, real lizards, and mammals all survived and later grew significantly larger. These dinosaurs had existed for tens of millions of years prior to this.
"How concentrated the events are is related to the magnitude of the environmental effects," said Paul Olsen, a paleontologist at Lamont-Doherty and a co-author of the study.
Due to their small size and ability to live in burrows, little feathered dinosaurs, turtles, real lizards, and mammals all survived and later grew significantly larger. These dinosaurs had existed for tens of millions of years prior to this.
"How concentrated the events are is related to the magnitude of the environmental effects," said Paul Olsen, a paleontologist at Lamont-Doherty and a co-author of the study.
"The same total volume of volcanism concentrated in less than a century has a far greater impact than small events spaced out over [tens of thousands of years]." The main conclusion is that the CAMP lavas are examples of extremely concentrated occurrences.
Source phys.org
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