On a recent trip to Idaho I saw this sign at a rest stop in central Washington:

Over 50 lava flows! Each of them from more that 100 miles to the east!
I knew Idaho was mostly covered by lava flows but I didn’t realize so much of Washington was too.
Yup. More than 100,000 cubic kilometers. According to https://en.wikipedia.org/wiki/Columbia_River_Basalt_Group , 174,300 cubic km.
Totally changed the state. All that heat would have created huge updrafts, resulting in massive and long-lasting high winds and torrential rains, which cooled the top layers, while the ground it flowed over cooled the bottom. That is why the basalt columns have small “crystals” (not really crystals, but you know what I mean) at top (rapid rain cooling), medium crystals at bottom (slower ground cooling) and the largest crystals in the middle of the flows.
Professor Nick Zentner has a YouTube series that goes into the geology of Washington State. It’s fascinating. We got into watching him during the pandemic. I think he had a PBS series as well.
Lava flows from eastern Washington made it all the way to the Oregon coast!
And, according to Wikipedia, it only took about a week!
Yeah, very fluid stuff!
And very hot, to retain that fluidity over that time and distance.