[mewzilla]

https://volcanoes.usgs.gov/volcanoes/yellowstone/yellowstone_hazard_44.html

LOL. The USGS is hedging its bets on the type of lava...

[NorthMountain]

No, they're not "hedging their bets". They're telling you that both types of lava flows have happened in the past at Yellowstone, and that they're very different from each other.

From the USGS link:

The most likely type of volcanic eruption at Yellowstone would produce lava flows of either rhyolite or basalt. These would be significant and produce flows with volumes greater than 1 km3, but all of these would most certainly remain within the boundary of Yellowstone National Park.

Since Yellowstone’s last caldera-forming eruption 640,000 years ago, about 30 eruptions of rhyolitic lava flows have nearly filled the Yellowstone Caldera. Other flows of rhyolite and basalt (a more fluid variety of lava) also have been extruded outside the caldera.