The largest eruption in the United States in the last 10,000 years was the Mount Mazama eruption, which created Crater Lake in Oregon. This eruption occurred approximately 7,600 years ago, and it's estimated to have been a VEI 7 eruption, meaning it released an enormous amount of material.

Here's why it's considered the largest:

* Magnitude: The eruption ejected an estimated 50-60 cubic miles of volcanic material, dwarfing the volume of most other eruptions in the US.

* Explosive Power: The eruption was so powerful that it collapsed the summit of the volcano, creating the caldera that now holds Crater Lake.

* Global Impact: The eruption likely had significant global effects, including potential climate change due to the vast amount of ash released into the atmosphere.

While other eruptions in the US, like the eruption of Glacier Peak in Washington State, have had a higher Volcanic Explosivity Index (VEI), they occurred further back in time than the Mount Mazama eruption, within the last 10,000 years.