Hidden Underwater Volcanoes May Explain Half of Earth’s Triassic Extinctions

Mass extinctions are often imagined as sudden, planet-wide catastrophes caused by asteroid impacts, supervolcanoes, or runaway climate change. But Earth’s history also includes a series of smaller extinction events that unfolded between the big five, when marine ecosystems repeatedly collapsed without a single obvious trigger.

New research suggests that repeated volcanic eruptions beneath ancient oceans drove many of the Triassic’s lesser-known extinction crises. In a study published in Geology, a team analyzed fragments of long-vanished ocean basins now preserved in the Tibetan Plateau, linking repeated pulses of underwater volcanism to recurring marine extinctions between about 250 and 200 million years ago.

Read More: 444-Million-Year-Old Microscopic Fossils Reveal Early Seafloor Recovery After Mass Extinction

Tracking Volcanic Activity Behind Triassic Extinctions

During the Triassic period, most of Earth’s landmasses were joined into the supercontinent Pangaea. An ocean system known as the Tethys lay between its drifting margins. As tectonic plates later converged, much of that oceanic crust was destroyed, leaving behind scattered fragments now preserved within mountain belts.

The team focused on these geological remnants, particularly within the Tibetan Plateau. The region preserves unusually complete records of the closure of the Meso-Tethys and Neo-Tethys oceans, making it one of the few places on Earth where traces of Triassic oceanic volcanism can still be studied.

By dating zircon and titanite minerals, the researchers identified three major episodes of underwater volcanism during the Triassic, at about 250 million to 248 million years ago, 233 million to 231 million years ago, and 210 million to 208 million years ago. Each episode marks the formation of a marine large igneous province, or LIP, a massive volcanic plateau created on the seafloor by hot material rising from deep within Earth.

When Volcanoes Alter the Seas

To assess the biological consequences of these eruptions, the researchers compared their timing with fossil records and chemical clues preserved in marine sediments. At least four marine extinction events occurred close in time to these volcanic pulses.

The eruptions did not wipe out life by physically covering the seafloor with lava. Instead, they likely disrupted the oceans indirectly. As magma erupted beneath the sea, it released greenhouse gases and altered ocean chemistry. The resulting warming and nutrient influx would have fueled algal growth, followed by widespread oxygen depletion as that organic matter decayed.

These low-oxygen and sulfur-rich conditions created environments that many marine organisms could not survive in. Species with limited mobility or narrow tolerance for chemical stress were especially vulnerable. According to the study, marine large igneous provinces account for roughly half of the Triassic extinction events that have an identifiable geological trigger.

Rethinking Extinctions in Deep Time

Marine large igneous provinces are difficult to detect because most of them no longer exist. Unlike volcanic provinces on land, oceanic plateaus are typically destroyed as tectonic plates converge. Only fragments remain, preserved where ancient oceans were squeezed shut and uplifted into mountain ranges.

The authors suggest that many additional marine volcanic events likely occurred but left no surviving trace. If so, their influence on Earth’s biological history may be broader than currently recognized, extending beyond the Triassic to other extinction events that lack obvious causes.

By linking repeated marine extinctions to underwater volcanism in long-lost oceans, the study clarifies how some of Earth’s lesser-known extinction events unfolded. It suggests that life on Earth has been shaped not only by rare catastrophes but also by recurring environmental disruptions that played out over millions of years.

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Article Sources

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• This article references information from the recent study published in Geology: Marine large igneous provinces: Key drivers of Triassic recurrent extinction