The largest eruption over the past 2 centuries was Tambora in Indonesia in 1815. Large volcanic eruptions are more frequent than asteroid impacts of similar magnitude. Tambora
The biggest eruption was at Yellowstone about 2.2 million years ago. An explosive eruption produced 2,500 cubic kilometers of ash ! (That’s about 2,500 times more ash than Mount St. Helens erupted!). Yellowstone has had three very large eruptions in the last 2 million years. These eruptions occurred 2.2, 1.2, and 0.6 million years ago. Only four eruptions in the last 10,000 years have been assigned a Volcanic Explosivity Index of 7. The Tambora eruption was the largest in modern history. According to the Global Volcanism Program, it was the only eruption in at least 1,000 years to rate a VEI 7. The eruption of Mt. Tambora in what is now Indonesia cast a veil of ash around the world, lowering global temperatures by more than 5 degrees Fahrenheit. The Largest Volcano Eruptions-John Seach. The size of volcanic eruptions is determined by the amount of lava emitted. The largest eruption over the past 2 centuries was Tambora in Indonesia in 1815. Large volcanic eruptions are more frequent than asteroid impacts of similar magnitude. Table 1. Large eruptions in past 10,000 years.
http://volcano.oregonstate.edu/what-largest-eruption-ever http://www.csmonitor.com/Science/2010/0418/Five-biggest-volcano-eruptions-in-recent-history http://volcanolive.com/large.html
what is the biggest volcanic eruption