What happened 200 million years ago which led to unexplained marine extinctions? Answer lies near a lake in Tibet

Around 200 million years ago, long before dinosaurs ruled the land, Earth’s oceans went through a series of sudden and damaging die-offs. Many marine species, including shell-bearing animals, reef builders, and microscopic plankton, disappeared in waves. These extinctions puzzled scientists for decades because they did not match obvious causes like asteroid impacts or giant volcanic eruptions on land. The clues, it turns out, were buried, and later lifted, in an unexpected place: near a remote lake in Tibet.

Today, Tibet sits more than 4,000 meters above sea level. But 200 million years ago, this region was deep beneath the ocean, part of the vast Tethys Ocean. The collision of the Indian and Eurasian plates that formed the Himalayas led to the pieces of the ancient seafloor pushed upward and preserved in the mountains.

Scientists studying rocks near a Tibetan lake found chemical signatures and rock types that only form on the ocean floor, especially during extreme volcanic activity. These rocks act like a frozen record of ancient disasters, offering rare insight into events that normally vanish as seafloor sinks back into Earth’s mantle.

Massive underwater volcanic eruptions

Research "Marine large igneous provinces: Key drivers of Triassic recurrent extinction", published in the journal Geology has identified remnants of massive underwater volcanic eruptions in these ancient rocks. These volcanic events occurred in multiple episodes during the Triassic, roughly 250-248 million years ago, 233-231 million years ago, and 210-208 million years ago.

Each episode marked the formation of what scientists call marine large igneous provinces (LIPs), which form when enormous amounts of magma erupt underwater, spreading lava across thousands of square kilometers of seafloor.

Such underwater volcanism doesn’t produce dramatic eruptions above the sea surface, but it releases vast amounts of greenhouse gases and chemical elements directly into seawater. This can warm the oceans, reduce oxygen levels, and alter nutrient cycles, conditions that make it difficult for many marine species to survive.

When researchers matched the timing of these LIP events with fossil and chemical records from ancient sedimentary rocks, they found that at least four episodes of marine extinction coincide closely with these volcanic pulses. Marine LIPs may therefore explain about half of the Triassic extinctions with identifiable geological triggers.

Together, these changes created toxic marine conditions, killing large portions of ocean life. Scientists now believe these volcanic events explain many of the previously unexplained marine extinctions during the Late Triassic period.

Why scientists missed this for so long

Most ancient ocean crust is destroyed over time as tectonic plates sink into Earth’s mantle. That means evidence of underwater disasters is usually erased. The Tibetan Plateau is special because plate collisions saved pieces of this ancient seafloor, allowing scientists to study them hundreds of millions of years later.

Understanding how ancient oceans collapsed helps scientists better predict how modern oceans might respond to rapid warming, rising carbon levels, and oxygen loss. The past shows that when ocean chemistry changes too quickly, marine ecosystems can collapse, even without an asteroid impact.