It's difficult to comprehend what 1,000 cubic kilometers of rock would look like. It's even more difficult to imagine it being violently flung into the air. Yet the Yellowstone volcanic system blasted more than twice that amount of rock into the sky about 2 million years ago, and it has generated a number of massive (if somewhat smaller) eruptions since, and there have been even larger eruptions deeper in the past.
All of which might be enough to keep someone nervously watching the seismometers scattered throughout the area.