What is the name of the volcano that formed the largest known volcanic deposit?
Answer
La Garita Caldera
The volcano that formed the largest known volcanic deposit is the La Garita Caldera in Colorado, United States.
La Garita formed about 28 million years ago during an enormous explosive eruption in the San Juan volcanic field. That eruption produced the Fish Canyon Tuff, a vast sheet of welded volcanic ash and pumice known as an ignimbrite. The volume and reach of this deposit make the eruption one of the largest explosive volcanic events known from Earth’s geological record.
A caldera is not a conventional cone-shaped volcano. It is a large depression formed when the ground collapses after an eruption empties or partly drains a magma reservoir beneath it. In La Garita’s case, the collapse followed the eruption that produced the Fish Canyon Tuff.
La Garita is sometimes confused with famous active or recently active calderas such as Yellowstone, Toba, and Long Valley. Those are also associated with immense eruptions, but La Garita is the canonical answer for the exceptionally large Fish Canyon Tuff deposit.