Every few tens of millions of years, Earth hemorrhages millions of cubic kilometers of lava. These "flood basalts" trigger mass extinctions. What causes them? Giant plume heads from the core-mantle boundary, or plate tectonics gone wrong?
The planet's fiery pulse
Large Igneous Provinces (LIPs) are immense outpourings of magma that occur over geologically short timeframes—typically within one to five million years. These are not volcanoes; they are flood basalts that can cover areas the size of continents and reach thicknesses of several kilometers. The Siberian Traps, for instance, erupted around 252 million years ago and represent the largest known continental volcanic event in Earth's history. Estimates suggest it originally covered about 7 million square kilometers and contained a magma volume of around 4 million cubic kilometers, enough to cover the continental United States in a kilometer-deep layer of rock.
LIP eruptions often coincide with severe environmental crises and mass extinctions. The Siberian Traps are the primary suspect for causing the end-Permian extinction, or "The Great Dying," which eliminated over 96% of marine species and 70% of terrestrial species. The Deccan Traps in India, which unleashed more than 1.1 million cubic kilometers of lava, were erupting around the time the non-avian dinosaurs went extinct 66 million years ago. While the Chicxulub asteroid impact is considered the primary trigger for that extinction, the massive release of climate-altering gases from the Deccan volcanoes likely contributed to the environmental stress. These eruptions release vast quantities of sulfur dioxide and carbon dioxide, leading to acid rain and dramatic shifts in global temperature.
A deep and heated debate
The cause of these colossal eruptions is a topic of intense scientific debate, primarily centered on two competing ideas: the mantle plume hypothesis and the plate hypothesis.
The mantle plume hypothesis suggests that LIPs are the surface expression of giant, buoyant blobs of hot rock that originate from the core-mantle boundary, some 2,900 kilometers deep. According to this model, a plume's massive, spherical head ascends through the mantle and flattens against the underside of the lithosphere (Earth's rigid outer layer). This triggers widespread melting and results in the rapid eruption of enormous volumes of basaltic lava. The narrow tail of the plume can remain active for tens of millions of years, creating a chain of volcanoes like the Hawaiian Islands.
The alternative, called the plate hypothesis, posits that LIPs can be explained by processes occurring in the upper mantle related to the movement of tectonic plates. This collection of theories suggests that factors like the cracking of continents (rifting), the peeling away of dense lithospheric rock (delamination), or the melting of subducted oceanic plates could generate massive amounts of melt without requiring a deep-seated plume. Proponents of this view note that many LIPs occur along the edges of continents or at locations of tectonic stress, suggesting a link to plate tectonics. The debate continues as scientists gather more geochemical and seismic data to understand the ultimate triggers of Earth's most catastrophic volcanic events.
💡Fun Facts
The largest LIP on Earth is the Ontong Java Plateau, a submarine formation in the Pacific Ocean roughly the size of Alaska.
The eruptions that formed the Deccan Traps in India occurred in four main pulses, each lasting about 100,000 years.
The Columbia River Basalt Group in the U.S. Pacific Northwest consists of more than 350 individual lava flows that erupted between 17 and 6 million years ago.
The gases released during LIP eruptions can cause an average global temperature drop of about 2°C due to sulfur dioxide, followed by long-term warming from carbon dioxide.
The geological remnants of Large Igneous Provinces are always accessible for observation.
Admission
Free
Accessibility
Varies dramatically. Some LIP formations, like the Columbia River Basalts, are visible in road cuts and public parks in Washington and Oregon. Others, like the Siberian Traps, are in remote wilderness.