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Volcanic events 450 million years ago triggered wipe-out of 85% of marine life

ScientiFix, our weekly feature, offers you a summary of the top global science stories of the week, with links to their sources.

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New Delhi: Scientists have found that two intense periods of volcanism likely triggered a period of global cooling and falling oxygen levels in the oceans — which caused one of the most severe mass extinctions in Earth’s history.

The researchers studied the effects of volcanic ash and lava on ocean chemistry during a period of extreme environmental change around 450 million years ago.

This period brought about intense planetary cooling, which led to a mass extinction event. During this, about 85 per cent of species dwelling in the oceans were wiped out, reshaping the course of evolution of life on Earth.

Previously, researchers have suggested that global cooling was driven by an increase in phosphorus in the oceans. Phosphorus — one of the key elements of life — determines the pace at which tiny aquatic organisms like algae can use photosynthesis to convert carbon dioxide (CO2) into organic matter. 

These organisms eventually settle to the seabed and are buried, ultimately reducing the levels of carbon dioxide in the atmosphere, which then causes cooling.

However, the team found that two large bouts of volcanic activity across the globe, occurring in parts of present-day North America and southern China, coincided very closely with the two peaks in glaciation and extinction.

The team discovered that widespread blankets of volcanic material laid down on the seafloor during the Ordovician Period would have released sufficient phosphorus into the ocean to drive a chain of events, including climatic cooling, glaciation, widespread reduction in ocean oxygen levels, and mass extinction. Read more here

Also read: An ancient mammoth tusk buried deep in Pacific Ocean & ‘newcomer’ dwarf galaxies in Milky Way

Mysterious footprints found to be early humans

There may have been more than one type of early human species coexisting some 3.7 million years ago, according to researchers who re-examined fossilised footprints that were discovered in 1976 in Tanzania. 

The oldest evidence of upright walking in the human lineage are footprints of an ancient human species called Australopithecus afarensis — the species of the famous partial skeleton ‘Lucy’. Some footprints found at Laetoli, Tanzania in 1978 have been attributed to this species. 

Another set of mysterious footprints was partially excavated at the nearby Site A in 1976, but was dismissed as possibly being made by a bear walking upright on its hind legs, because the tracks were so different.  

To determine what left these footprints, a team from the University of Colorado Denver went to the site and re-excavated and fully cleaned the five consecutive footprints. 

They identified evidence that the fossil footprints were made by an early human species — including a large impression for the heel and the big toe. The footprints were measured, photographed and 3D-scanned.

The researchers then identified four semi-wild juvenile black bears, with feet similar in size to that of the footprints. Each bear was lured with maple syrup or apple sauce, to stand up and walk on their two hind legs across a trackway filled with mud to capture their footprints.

The researchers captured over 50 hours of video on wild black bears. They realised that the bears walked on two feet less than 1 per cent of the total observation time, making it unlikely that a bear made the footprints at Laetoli. This is because no footprints were found of this individual walking on four legs. 

As bears walk, they take very wide steps, wobbling back and forth. They are unable to walk with a gait similar to that of the footprints that the researchers found. Similar research with chimpanzees further confirmed that these footprints actually belonged to early humans who were different from Lucy’s species. Read more here.

A new dinosaur with a deadly armoured tail

Palaeontologists in Chile have discovered the remains of a dinosaur with a deadly armored tail that has not been seen in any dinosaur before. 

According to the team, the tail would have looked like a flat sword.

The dinosaur’s remains helped researchers learn more about the history of the evolution of ankylosaurs, the group to which it belongs.  

According to the team, the remains suggest that when the supercontinent Pangaea broke apart during the Jurassic period — that is 201.3 million to 145 million years ago — it led to extreme differences between ankylosaurs on the northern supercontinent, Laurasia, and those on the southern supercontinent, Gondwana.

The new species has been named Stegouros elengassen. Its well-preserved skeleton is about 80 per cent complete, and was found in rocks dating to between 71.7 million and 74.9 million years ago in February 2018.  The specimen was a roughly 6.5-foot-long ankylosaur.

By reconstructing the skeleton, researchers were able to make a 3D artist impression of how the dinosaur might have looked. Read more here

Also read: Rare tardigrade fossil found in 16-million-year-old Dominican amber

Massive black hole found at heart of Milky Way’s dwarf satellite galaxy

Scientists have discovered an unusually massive black hole at the heart of one of the Milky Way’s dwarf satellite galaxies, called Leo I. 

According to researchers, the finding could redefine our understanding of how all galaxies evolve. 

Unlike most dwarf galaxies orbiting the Milky Way, Leo I does not contain much dark matter. By measuring its gravitational pull on the stars, researchers were able to get an estimate of its dark matter content. 

The faster the stars are moving, the more matter there is enclosed in their orbits. The team wanted to know whether dark matter density increases toward the galaxy’s centre. 

While studying data from the galaxy, the researchers realised that it has a disproportionately massive black hole at its centre — about as massive as the Milky Way’s black hole. 

The researchers said the result was different from past studies of Leo I due to a combination of better data and supercomputer simulations. 

The findings change what astronomers understand about the evolution of galaxies, as “there is no explanation for this kind of black hole in dwarf spheroidal galaxies”, according to the team. Read more here

Half of Earth’s water may have come from the Sun

Researchers propose that a rain of protons from the Sun may be producing water all the time on rocks and dust throughout the Solar System. They say that up to half of Earth’s water may have been produced this way.

Water-rich asteroids are currently the best candidates for the delivery of water as well as carbon-hydrogen compounds, which together make life possible on Earth. 

However, water from asteroids contains a specific ratio of ordinary hydrogen to a heavier kind — or isotope — called deuterium. 

If all of Earth’s water were from asteroids, we would expect it to have this same ratio. But Earth water has less deuterium, so there must also be some other source of water in space.

The only body in the Solar System with a lot of hydrogen but a lower ratio of deuterium than Earth is the Sun. Researchers now propose that solar winds may have been the source of half of the planet’s water.  Read more here

(Edited by Rohan Manoj)

Also read: Scientists create ‘concrete’ using blood, sweat, tears of astronauts for construction on Mars


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