How much volcanic activity has there been at Yellowstone since the most recent giant eruption?
Since the most recent giant caldera-forming eruption, 640,000 years ago, approximately 80 relatively nonexplosive eruptions have occurred. Of these eruptions, at least 27 were rhyolite lava flows in the caldera, 13 were rhyolite lava flows outside the caldera and 40 were basalt vents outside the caldera. Some of the eruptions were approximately the size of the devastating 1991 Pinatubo eruption in the Philippines, and several were much larger. The most recent volcanic eruption at Yellowstone, a lava flow on the Pitchstone Plateau, occurred 70,000 years ago.
