Taxonomy term

mass extinction

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

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.

08 Jul 2016

Volcanic aerosols not enough to cause mass extinctions?

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.

25 Feb 2016

Permian-Triassic extinctions timed differently on land and at sea

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.
 
31 Jan 2016

Great drying led to great dying down under

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.
 
08 Jul 2015

Geomedia: Books: Are we causing a sixth extinction?

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.

20 Dec 2014

Do impacts trigger extinctions? Impact theory still controversial

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.

This back-and-forth ideological debate describes both the historical and still-ongoing struggle over a purported cause of mass extinctions: the meteor impact theory.

23 Jun 2010

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