Supervolcanos are formed when massive amounts of pressure build up under the Earth’s surface. Often times, as in the case with the Yellowstone Caldera, supervolcanos have erupted several times in their past. However, “past” when talking about the Earth generally means several hundred million years, which is why so much pressure has built up. But not all eruptions are the explosive kind we think of when we hear the word. Some eruptions can last millions of years.
Large igneous provinces, or LIPs, are formed by massive flows of debris, mainly igneous rock, which emit from the Earth’s surface. These accumulations of rock can cover several hundred thousand square kilometers. In fact, in order to be classified as a LIP, igneous rock accumulations must be larger that 100,000 square kilometers, or roughly the size of Iceland.
Supervolcanos exist throughout the world, though most haven’t been active for thousands, if not millions of years. The most recent supereruptions both occurred in Indonesia, at Mt. Tambora and Mt. Rinjani, in 1815 and 1257 respectively. Both of these eruptions were so large that they caused extreme weather events whose effects were felt around the globe.
The amount of “ejecta” released by supereruptions can be so massive that it affects weather around the globe. The 1257 eruption of Mt. Rinjani is thought to be the cause of the “little ice age”, a period of cooling that affected Europe for over 500 years. Mt. Tambora’s eruption in late 1815 caused 1816 to be called “the year without a summer”.