Voluminous outpourings of magma have occurred both on the continents and in the oceans during Earth’s history. The formation processes for these large igneous provinces are still debated, but their relevance and environmental impact are obvious. The magmatism associated with the formation of large igneous provinces is thought to have transferred about 10% of the mass and energy from the Earth’s deep interior to the surface. The eruption of such large volumes of magma has released enormous amounts of heat and volatile gases, and could have triggered methane release from seafloor gas hydrates, thus significantly altering Earth’s climate in the past. It is therefore important to understand the chronological, petrological and geodynamic development of large igneous provinces. Writing in Nature Geoscience, Sager et al. report that the Tamu Massif, part of the Shatsky Rise large igneous province in the north-western Pacific Ocean, was formed by a single, massive pulse of magmatism about 145 million years ago.