[6] The caldera was preceded by a lava dome that had been built by volcanic eruptions of rhyolite starting about 19 million years ago.

[6] A lake subsequently formed in the caldera, and it deposited varved sediments, diatomite, opal, carbonaceous material, and mafic lavas.

The age of the uranium formation is assumed to be the same as the caldera tuff, which is approximately 16.1 million years.

[7] Other deposits in the caldera contain ores of antimony, cesium, and lithium[11][12] (potentially, one of the biggest mines in the world).

[13] The Thacker Pass lithium deposit, located within the caldera, is a prospect that in 2017 was said to be the most significant lithium-clay resource in the U.S.[14]