The Triassic was a period of recovery and rebuilding after the most severe extinction in Earth history, yet it never settled into stability. New research published in Geology shows that the planet’s oceans were repeatedly destabilized by enormous undersea volcanic events that unfolded far from sight. These eruptions reshaped marine ecosystems, changed the chemistry of entire ocean basins, and triggered several major biological crashes that have never been fully explained. The study offers a detailed reconstruction of ancient volcanic provinces that once existed across the Meso Tethys and Neo Tethys oceans. These seas vanished long ago, but pieces of their volcanic landscapes remain preserved in the Tibetan Plateau. The new work pieces those fragments together and presents a clear pattern of repeated volcanic disturbance during the Triassic.
The team examined remnants of oceanic islands, submarine plateaus, and seamount chains that formed during three distinct volcanic phases. These phases occurred at 250 to 248 million years ago, 233 to 231 million years ago, and 210 to 208 million years ago. Each event produced significant volcanic buildup across the ocean floor and released enormous quantities of heat and gas into the overlying water. These eruptions did not push ash into the atmosphere in the way continental eruptions do. Instead, they injected gases directly into seawater, which produced rapid changes in temperature and chemistry. Those changes reached thresholds that marine organisms could not survive. The new analysis links each volcanic pulse to a known drop in biodiversity across the Triassic fossil record.
The early Triassic was already a vulnerable period. The planet had just emerged from the end Permian extinction, a global catastrophe that erased more than ninety percent of marine species. The surviving ecosystems were fragile and slow to reorganize. The discovery that another major volcanic event unfolded only a few million years later at 250 to 248 million years ago adds new context to that struggle. The first wave of volcanic activity described in the study produced extensive undersea plateaus and a rapid deterioration of water chemistry. Ocean circulation slowed and deep water became oxygen starved. Sulfur compounds increased as microbial processes shifted under the new chemical regime. The result was a return to conditions that stressed nearly every marine group. Several lineages that had started to recover after the Permian collapse were hit again, leaving an uneven and delayed path toward ecological rebuilding.
The second volcanic phase at 233 to 231 million years ago coincides with the Carnian Pluvial Episode, a time known for abrupt climate disruption and significant biological turnover. The new study helps clarify the mechanisms behind those changes. The buildup of volcanic plateaus produced long lasting effects on ocean composition. Gas release from these eruptions drove a strong expansion of anoxic and euxinic waters. These toxic zones spread through shallow and deeper basins alike. Organisms that were already coping with unstable climates were overwhelmed by this sudden change in marine chemistry. Coral reefs suffered heavy losses. Ammonoids experienced a major reduction in diversity. Many groups of marine reptiles also declined as food webs contracted. The study presents strong geological evidence that the volcanic pulse did more than influence climate. It directly altered the physical and chemical state of the oceans and initiated a chain of ecological failures.
The final pulse at 210 to 208 million years ago marks another significant turning point. This interval lines up with biological stresses documented near the end of the Triassic. Although it did not produce a global collapse on the scale of the end Triassic extinction, the new findings show it contributed to a major reduction in marine biodiversity. Once again, the eruptions built large volcanic plateaus on the seafloor. These structures altered local circulation patterns, introduced massive amounts of volcanic fluids into surrounding basins, and destabilized ecosystems that were already sensitive to environmental fluctuation. Fossil records from this period show a clear reduction in several marine groups and a noticeable shift in ocean chemistry indicators. The new study connects these observations to a clear geological trigger.
A central achievement of this research is its reconstruction of ancient volcanic provinces that vanished through tectonic recycling. Most oceanic crust older than two hundred million years has been subducted into the mantle. That process removes nearly all direct evidence of early ocean basins. In rare cases, fragments of oceanic plateaus are uplifted during continental collisions. These fragments are the only surviving records of vast volcanic structures that once shaped entire basins. The Tibetan Plateau holds several of these remnants. They include basalts with distinctive chemical signatures that match the composition of large igneous provinces. The researchers compared these remnants with global datasets on sediment chemistry, fossil distribution, and oceanographic indicators. The correlations were consistent across multiple lines of evidence.
One of the most significant implications of this work is the recognition that many marine volcanic events may be missing from the geological record. Because undersea eruptions often occur on oceanic crust that is later destroyed by subduction, only fragments of these events survive. The team argues that many uplifted mountain belts around the world likely contain pieces of ancient oceanic volcanic provinces. These pieces are scattered, altered, and often difficult to identify. As a result, many volcanic triggers for past biological crises may have gone undetected. The authors propose that a substantial portion of Phanerozoic extinctions may have originated from undersea eruptions that no longer have visible geological traces. This interpretation suggests that Earth’s extinction history is more tightly connected to deep ocean volcanism than previously recognized.
The study also highlights the unique impact that undersea large igneous provinces have on the environment. Continental eruptions release gases into the atmosphere, where they influence climate on global scales. Marine eruptions release gases directly into seawater, creating immediate chemical disruption. These eruptions can collapse oxygen levels in a matter of months and generate toxic conditions that spread quickly through connected basins. This direct assault on marine chemistry is particularly effective at triggering biological crises. Species that rely on stable oxygen levels, such as many invertebrates and marine reptiles, are among the first to disappear. Food webs collapse as primary producers decline. Even organisms that survive the initial shock face long term stress as the environment remains unstable for thousands of years.
This discovery changes the way geologists view the Triassic period. Instead of a slow recovery followed by occasional setbacks, the new evidence shows a phase marked by repeated environmental shocks delivered from deep beneath the oceans. Each volcanic pulse generated a chain reaction. Chemical disruption forced rapid changes in circulation. Oxygen poor waters expanded into previously habitable zones. Toxic compounds built up. Organisms that lived through one event were forced to endure another only a few million years later. The pattern shows a planet struggling to maintain ecological balance while powerful forces on the ocean floor repeated the cycle of disruption.
The study strengthens the case that large igneous provinces play a central role in shaping life’s long term trajectory. Many of the major extinctions in Earth history already have known links to volcanic events on land. The new research shows that marine eruptions were equally capable of producing catastrophic results. Since these events are more easily erased by subduction, their influence has likely been underestimated. The Triassic record now demonstrates that undersea volcanism is not merely a background process. It is a driver of large scale change that can restructure ecosystems across entire oceans.
The work also opens new research directions. If ancient volcanic provinces are preserved only in fragmented form, then identifying them requires detailed mapping of mountain belts around the world. Chemical signatures within uplifted basalts may offer clues about their origins. Matching these signatures with global extinction patterns could reveal new links between undersea volcanism and biodiversity loss. This approach may help explain several extinction events that currently have no confirmed geological trigger. The identification of missing volcanic provinces would provide a more complete understanding of how Earth’s interior processes have influenced the evolution and stability of life.
This study presents a clear and coherent interpretation of Triassic instability. The oceans were not tranquil environments recovering from a single catastrophe. They were dynamic systems exposed to repeated volcanic disturbances that unfolded across millions of years. Each event forced rapid environmental shifts that pushed ecosystems to their limits. The geological record preserved in the Tibetan Plateau allows scientists to reconstruct these events with new precision. The result is a clearer understanding of the forces that shaped early Mesozoic life and a renewed appreciation for the influence of deep ocean volcanism on the history of the planet.
SourceÂ
Fan, J. J., Sun, S. L., Zhou, J. B., Wilde, S. A., Wang, Y., & Lv, J. P. (2026). Marine large igneous provinces: Key drivers of Triassic recurrent extinction. Geology.
https://doi.org/10.1130/G53406.1
