Mass Extinction on EARTH Magazine

Geomedia: Books: A witty look at "The Ends of the World"

Wed, 13 Feb 2019 14:59:21 -0500

"The Ends of the World: Volcanic Apocalypses, Lethal Oceans, and Our Quest to Understand Earth's Past Mass Extinctions," by Peter Brannen, Ecco/Harper-Collins, 2017, ISBN 9780062364807; paperback published 2018, ISBN 9780062364814

Our planet has been through some harrowing episodes, particularly in the form of mass extinctions since the advent of multicellular life. How organisms came to perish in these events should interest all conscious, intelligent forms of multicellular life lucky enough to still be alive — you and I included. A great way to satisfy that interest is with “The Ends of the World: Volcanic Apocalypses, Lethal Oceans, and Our Quest to Understand Earth’s Past Mass Extinctions” by Peter Brannen, a well-paced, well-sourced and well-written guide to mass extinctions.

Free swimmers came back first after Great Dying

Thu, 17 Jan 2019 13:23:48 -0500

In the Early Triassic, following the end-Permian extinction, nektonic marine life recovered fastest, according to new research, resulting in a reversed functional pyramid. Percentages represent the proportion of marine genera belonging to each class of organisms. Credit: courtesy of Haijun Song.

About 252 million years ago, at the boundary between the Permian and Triassic periods, the vast majority of marine and terrestrial life died out in the most devastating extinction event in Earth’s history. Earth’s ecosystems eventually recovered, but not in the way — or as quickly as — scientists thought. In a new study looking at how marine species reemerged in the Triassic, researchers report a surprising trend of recovery from the top of the food chain down.

Mercury links Big Five extinction events

Fri, 03 Aug 2018 13:33:32 -0400

The locations of sites studied for mercury abundances are shown in yellow on this plate reconstruction from the time of the Frasnian-Famennian extinction. Credit: Racki et al., Geology, April 2018.

Mercury concentration spikes in the geologic record have been linked to massive volcanism in the form of large igneous provinces (LIP) such as the Deccan Traps, a kilometers-thick heap of basalt layers that formed in what is now India beginning late in the Cretaceous, and the Siberian Traps, an even larger mass of lava that erupted in Siberia at the end of the Permian. It’s thought that vast gas emissions associated with LIP eruptions could have significantly changed climate patterns and affected conditions such as ocean acidity. And four out of five of the most devastating extinction events of the last 550 million years have previously been linked, at least partly, to the formation of LIPs. A new study looking at mercury in rocks dating to the Late Devonian has now linked the fifth to volcanism as well.

Down to Earth With: Jessica Whiteside

Wed, 23 May 2018 14:59:19 -0400

Jessica Whiteside (middle) is an assistant geology professor at Brown University. Credit: Courtesy of Jessica Whiteside

From Morocco to Connecticut, Jessica Whiteside has explored almost every Mesozoic rock outcrop there is. And she’s only three years out of graduate school. With a bachelor’s degree from Mount Holyoke College in South Hadley, Mass., and two master’s degrees and a doctorate from Columbia University in New York, N.Y., under her belt, Whitehouse is now in Providence, R.I., working as an assistant professor of geological sciences at Brown University.

Hot tropics drove out ancient reptiles, but they came back

Tue, 10 Apr 2018 11:33:16 -0400

Terrestrial reptiles vacated the tropics (orange and yellow belts) following the end-Permian mass extinction 252 million years ago. Credit: MUSE Archive.

About 252 million years ago, massive volcanic eruptions in what is now Siberia rapidly warmed Earth, resulting in the end-Permian mass extinction that saw most terrestrial and marine species die off. It’s been thought that surviving reptiles and fish fled the hot tropics and didn’t return for millions of years. But according to new research, the tropical evacuation may not have lasted so long after all.

Volcanic activity contributed to first of the "Big Five" mass extinctions

Wed, 15 Nov 2017 13:52:36 -0500

Researchers found mercury concentration spikes in Late Ordovician rock sampled from this site in Nevada's Monitor Range, indicating a possible role for large-scale volcanic activity in a mass extinction roughly 444 million years ago. Credit: David S. Jones

During the Ordovician, between about 488 million and 444 million years ago, plant life first emerged on land, while primitive fish and a variety of marine invertebrates flourished in the oceans. Toward the end of the period, however, a mass extinction — the first of the so-called “Big Five” Phanerozoic extinctions — wiped out roughly 60 percent of all marine invertebrate genera. In a recent study, researchers shed new light on a possible cause of the Late Ordovician extinction: volcanic activity.

Volcanism triggered end-Triassic extinction

Thu, 14 Sep 2017 11:47:17 -0400

These continental sedimentary layers in Morocco spanning the end-Triassic mass extinction event were analyzed for mercury content in a new study. Credit: Jessica Whiteside.

The end-Triassic mass extinction exterminated up to three-quarters of all species on land and in the oceans 201 million years ago. This die-off opened up ecological niches and allowed for, among other changes, dinosaurs to diversify and spread across terrestrial ecosystems during the rest of the Mesozoic. Volcanism has long been implicated in the extinction, but whether it had a major impact on the planet at the time has remained unclear. In new research, scientists observed elevated mercury concentrations in extinction-aged rocks from around the world. Because volcanism is the main nonanthropogenic source of mercury in the environment, the findings suggest that volcanic activity was likely the main extinction trigger at the end of the Triassic.

Hangover echinoderms survived the Great Dying

Mon, 19 Jun 2017 20:33:54 -0400

Triassic asterozoans like these, along with other "hangover" echinoderm species, descended from Paleozoic lineages once thought to have gone extinct at the end of the Permian. Credit: Thuy et al., ©Geological Society of America, 2017.

The end-Permian extinction event was disastrous for a wide range of organisms on land and in the sea, with as many as 70 percent of terrestrial and 81 percent of marine species dying off. One of the hardest hit marine phyla was the echinoderms, which today includes sea urchins and starfish. Echinoderms are thought to have suffered one of the most severe population reductions in evolutionary history, with only a few members surviving to repopulate the oceans in the Triassic. But in a new study, researchers have identified Triassic fossils from a handful of “hangover” species whose ancestors were previously thought to have gone extinct at the end of the Permian, suggesting the extinction wasn’t quite as cataclysmic for echinoderms as paleontologists have suspected.

Geomedia: Books: Exploring "The Worst of Times"

Wed, 25 Jan 2017 15:13:01 -0500

"The Worst of Times: How Life on Earth Survived Eighty Million Years of Extinctions," by Paul B. Wignall, Princeton University Press, May 2017, paperback, 978-0691176024. (Hardcover, 2015, 978-0691142098).

Every reader of this magazine knows something about mass extinctions. But few of us know as much as Paul B. Wignall, a professor of paleoenvironments at the University of Leeds in England who studies mass extinctions. In 1997, he co-authored with Anthony Hallam a scholarly volume titled “Mass Extinctions and their Aftermath.” Now, his first book aimed at a popular audience, “The Worst of Times: How Life on Earth Survived Eighty Million Years of Extinctions,” has been issued in paperback.

Downgrading the Great Dying

Wed, 18 Jan 2017 14:45:23 -0500

Estimates of species losses during six mass extinctions are lower when background extinctions are subtracted from previous estimates. Credit: Steven Stanley.

The end-Permian extinction, nicknamed the “Great Dying,” is thought to be the deadliest mass extinction in Earth’s history. Many textbooks claim that up to 96 percent of marine life died out during this event, but a new study suggests this cataclysmic number has been overestimated.

Nutrient deficiency delayed life after mass extinction

Tue, 15 Nov 2016 18:16:07 -0500

Stephen Grasby collects samples from an outcrop on northern Ellesmere Island in the Canadian High Arctic. Credit: John Spear, Colorado School of Mines.

After Earth’s most severe mass extinction, life took up to 9 million years to recover — millions of years longer than after other extinction events. New research published in Geology suggests that a collapse in the ocean’s productivity might have been the cause.

Ancient plankton communities stressed before mass extinction

Tue, 15 Nov 2016 10:34:44 -0500

These fossilized shallow-water graptolites found in Nevada are from the Ordovician. Credit: Charles E. Mitchell.

Changes in our modern ecosystems, such as declines in biodiversity and invasive species, are similar to those that preceded the first of Earth’s mass extinctions about 443 million years ago, according to a new study. Researchers recently found that ancient plankton communities began to show environmental stress nearly 400,000 years before the extinction, as the planet cooled.

When Earth hit the reset button on life: New research on the Permian-Triassic mass extinction

Fri, 14 Oct 2016 13:04:19 -0400

The mountains at Van Keulenhamna in southern Spitsbergen, Svalbard, expose the Permian-Triassic boundary, which forms the main step in the cliff line (V-shaped notch in middle of page) where Permian cherts give way to Triassic shales. Credit: Paul Wignall.

About five years ago, paleobiologist Matthew Clapham was walking along Panther Beach on California’s coast when something caught his eye. He reached down, picked it up, and quickly became overjoyed. It was a living brachiopod: a marine animal similar to bivalves that are so rarely encountered in today’s oceans that Clapham, who studies the fossils of animals like brachiopods at the University of California, Santa Cruz, had never found a living specimen before that day, and he has not found one since.

Antarctic no place to hide during end-Cretaceous extinction

Tue, 20 Sep 2016 16:13:52 -0400

Artist's rendering of a typical Cretaceous marine environment in Antarctica, including the paperclip-shaped "heteromorphy" ammonite Diplomoceras. Credit: James McKay (jamesmckay.info).

The end-Cretaceous extinction is famous for killing off the dinosaurs, but many other species perished as well. A new study in Nature Communications of marine fossils found in the Antarctic indicates that the extinction event was just as deadly for creatures in the polar regions.

Mammals hit harder than thought by end-Cretaceous extinction

Tue, 20 Sep 2016 15:09:59 -0400

This jaw fragment is part of a specimen of Didelphodon, a cat-sized marsupial predator that went extinct during the Cretaceous-Paleogene mass extinction. Credit: Nick Longrich.

Mammals, unlike the remaining nonavian dinosaurs and many other animals, are thought to have fared relatively well through the massive meteorite impact and protracted volcanism at the end of the Cretaceous 66 million years ago. After the extinction, mammals went on to dominate terrestrial ecosystems. But new research indicates that mammals might have taken a bigger hit than paleontologists have realized: Instead of about 75 to 85 percent of species going extinct, as prior studies suggested, it looks like about 93 percent of all mammal species may have gone extinct during the Cretaceous-Paleogene (K-Pg) extinction.

Weak magnetic field may have triggered Earth's first mass extinction

Thu, 16 Jun 2016 10:00:57 -0400

A section of the Ediacaran-aged Zigan Formation in the Ural Mountains of Russia. The Zigan was sampled by Joseph Meert and his team for paleomagnetic signatures. Credit: Mikhail Bazhenov.

For about the first 3 billion years of life, the only living organisms on Earth were microscopic. The Ediacaran Period, between 635 million and 541 million years ago, saw the rise of the first large-scale life, most of which then went extinct at the period’s close — a collapse that scientists have yet to explain. Now, researchers may have found one of the extinction’s drivers: rapid flip-flopping of Earth’s magnetic field — wherein the field’s north and south poles reverse — that could have left the planet and Ediacaran organisms vulnerable to bombardment by harmful cosmic radiation.

Volcanic aerosols not enough to cause mass extinctions?

Fri, 19 Feb 2016 18:35:29 -0500

Fresh basaltic lava degasses in the Holuhraun lava field in January 2015. The months-long Holuhraun eruption is a modern analog, albeit on a much smaller scale, of ancient flood basalt eruptions. Credit: Anja Schmidt, University of Leeds.

Mass extinctions — when more than half of Earth’s species disappear in a geologic instant — offer some of the planet’s most perplexing unsolved mysteries. Prolonged periods of volcanic activity have long been prime suspects for these ancient whodunits, the most recent of which finished off the last nonavian dinosaurs at the close of the Cretaceous about 66 million years ago. But scientists debate how drastic the environmental effects of such volcanism might have been, and whether other factors — like asteroid impacts, as in the end-Cretaceous extinction — played a big role as well.

Permian-Triassic extinctions timed differently on land and at sea

Thu, 31 Dec 2015 13:25:43 -0500

Sandstones and volcanic deposits at Old Lootsberg Pass in South Africa's Eastern Cape Province preserve fossil and geochronometric evidence suggesting that the Permian-Triassic terrestrial and marine extinctions were not simultaneous. Credit: Robert A. Gastaldo.

Life on land and in the sea was nearly eradicated about 252 million years ago in the largest-known mass extinction. The cataclysm, known as the Permian-Triassic (P-T) mass extinction, was likely driven by extensive flood basalt volcanism in Siberia and is thought to have affected global biodiversity simultaneously. However, based on analyses of rocks deposited around the time of the P-T boundary in the Karoo Basin of South Africa, scientists suggest in a new study that the terrestrial turnover in vertebrates occurred earlier than the marine extinction. If true, a second trigger — other than Siberian volcanism — might need to have occurred to explain both events.

Great drying led to great dying down under

Tue, 16 Jun 2015 13:07:22 -0400

If not for the megafaunal extinctions that wiped out many large animals at the end of the Pleistocene, the world might be a very different place today — with humans coexisting alongside still-living saber-toothed tigers, woolly mammoths and 3-meter-tall birds. The agents of these mass extinctions have been debated for decades: Were shifting climates, or our spear-wielding ancestors mainly responsible? A new study of the receding shorelines of Australia’s largest lake has found that a substantial drying of the environment, more so than human pressure, is mostly to blame for the loss of megafauna down under.

Geomedia: Books: Are we causing a sixth extinction?

Mon, 08 Dec 2014 11:55:35 -0500

"The Sixth Extinction: An Unnatural History," by Elizabeth Kolbert, Henry Holt and Co., 2014, 9780805092998.

Last year, Elizabeth Kolbert released her latest excellent book. Her previous volume, “Field Notes from a Catastrophe,” set a high bar for accessible, accurate science writing about environmental issues, but in my opinion, “The Sixth Extinction” surpasses it in several regards. Readers of this magazine will appreciate its solid geologic grounding and perspective, with entire chapters devoted to the end-Ordovician and end-Cretaceous extinctions, as well as sections on the principles of evolution and Earth history. Climate change, the focus of her earlier book, looms large here too, though it is just one of the many threats to the survival of our biosphere that Kolbert covers.

Do impacts trigger extinctions? Impact theory still controversial

Thu, 05 Jan 2012 06:41:58 -0500

AGI

The revolution started with a bang in 1980. For some, this revolution became a religion, even an orthodoxy. The true believers became proselytes and began to see signs supporting their viewpoint everywhere. But each time the proselytes claimed to have found yet another example in support of their “religion,” naysayers and doubters emerged. Two sides formed, each loudly castigating and questioning their opponents.