Category Archive 'Mass Extinctions'

13 Dec 2020

Scientists Find 27-Million-Year-Mass-Extinction Cycle


Forbes reports on an interesting new journal article.

Mass extinctions of land-dwelling animals—including amphibians, reptiles, mammals, and birds—follow a cycle of about 27 million years, coinciding with previously reported mass extinctions of ocean life, according to a new analysis published in the journal Historical Biology.

The study also finds that these mass extinctions align with major asteroid impacts and devastating volcanic eruptions.

Paleontologists recognize five big mass extinction events in the fossil record. At the end of the Ordovician period, some 443 million years ago, an estimated 86% of all marine species disappeared. At the end of the Devonian period, some 360 million years ago, 75% of all species went extinct. At the end of the Permian period, some 250 million years ago, the worst extinction event so far happened, with an extinction rate of 96%. At the end of the Triassic period, some 201 million years ago, 80% of all species disappeared from the fossil record. The most famous mass extinction happened at the end of the Cretaceous, some 65 million years ago, when 76% of all species went extinct, including the dinosaurs. Minor extinction events mark the end of the Carnian age, about 233 million years ago, and the transition from the late Eocene and early Oligocene period, about 36 to 33 million years ago, coinciding with the Popigai impact.

The authors examined the record of mass extinctions of land-dwelling animals and concluded that they coincided with the extinctions of ocean life. They also performed new statistical analyses of the extinctions of land species and suggest that those events followed a similar cycle of about 27.5 million years.

The authors also compared the ages of extinction events with the ages of impact craters, created by asteroids and comets crashing to the Earth’s surface, and the ages of flood basalts, the results of a giant volcanic eruption or series of eruptions that cover vast areas with lava and emit large quantities of greenhouse gases into Earth’s atmosphere.

“These new findings of coinciding, sudden mass extinctions on land and in the oceans, and of the common 26- to 27-million-year cycle, lend credence to the idea of periodic global catastrophic events as the triggers for the extinctions,” said Michael Rampino, a professor in New York University’s Department of Biology and the study’s lead author. “In fact, three of the mass annihilations of species on land and in the sea are already known to have occurred at the same times as the three largest impacts of the last 250 million years, each capable of causing a global disaster and resulting mass extinctions.”


29 Jul 2018

Glimpses of a Mass Extinction in Western New York

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Fossil tree stump, Gilboa, New York.

First, they came for the brachiopods…

In the New Yorker, Peter Brannan finds in Western New York State abundant evidence of Global Warming and planet-wide mass extinction having nothing whatsoever to do with human industrial production or the automobile.

[T]he Hudson Valley roughly marked land’s end, and, by now, I had pushed off this secret coastline to head west, and offshore. The red earth that earlier bracketed the highway—rumors of ancient rivers on land—now gave way to gray, banded rocks filled with seashells, where stacks of seafloor piled up, millennia-thick.

“The farther west you go in New York, it’s all marine fossils,” a paleontologist told me before I left. “New York would have been facing into a great continental sea. All the way out to Ohio, it’s all marine.”

This upstate ocean poked out from under farmland, and crumbled from rock walls behind gas stations. In the Devonian period—hundreds of millions of years ago—it was filled with sea lilies, sea scorpions, armor-plated monster fish, forests of glass sponges, and patch reefs of strange corals. At night, these reefs were cast in shimmering chiaroscuro, inviting moonlit patrols of sharks and coelacanths. Where the water met land in eastern New York, dawn revealed fish hauling ashore on nervous day trips—slimy, gasping astronauts under a withering sun.

In the ages since, the tropical inland sea drained away, the continents merged and rifted, and the seafloor turned to stone. As fish conquered the land at last, the ocean was buried and forgotten. …

The dramatic change roughly marks the Taghanic Event—a mass extinction that razed corals, brachiopods, and squid-like creatures stuffed in elegant shells all over the world. It was one of almost twenty global mass extinctions in the history of complex life, a list that includes five cataclysmic outliers, when the planet nearly died, and one that might someday include us. …

The great Devonian mass extinction remains something of a mystery. There were oxygen-starved oceans, fueled by an explosion of massive algae blooms—perhaps even driven by runoff from the land, as the emerging world of trees carried out their massive geoengineering project, greening the continents. Other research adds invasive species spread by surging seas, preposterous volcanoes and extreme climate change to the chaos for good measure. Whatever form this destroyer took, it laid waste to 99.99 per cent of the largest reef systems the world has ever known—the so-called “megareefs” of the Devonian, ten times more extensive than our own. Trilobites, tentacled drifters, fish wrapped in heavy armor—nothing was spared.


I still have somewhere boxes full of unprocessed limestone rocks full of Devonian brachiopods I collected back when I was in high school.

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