La-Garita-Caldera

37.756388888889 - 106.93416666667Koordinaten: 37 ° 45 ' 23 " N, 106 ° 56 ' 3" W

The La - Garita - Caldera is a large volcanic caldera in the San Juan Mountains in southwestern Colorado, USA is located. Before about 26 to 28 million years ago ( Oligocene ) found here a gigantic volcanic eruption of magnitude 8 on the Vulkanexplosivitätsindex place (super volcano).

In this eruption about 5,000 cubic kilometers of material (Fish Canyon Tuff ) were ejected. Thus, the eruption was twice as strong as the eruption of the Toba or 500 times as strong as the Pinatubo eruption of 1991. The Fish Canyon Tuff consists of dacite and is remarkably uniform in composition. Dacite is a silicon-rich volcanic rock that encountered in explosive eruptions, in Lavadomen and in short, thick lava flows.

The caldera is 35 by 75 kilometers in size and has an unusual for a caldera elongated shape. In the 1.5 million years of the Fish Canyon Tuff eruption there were at least seven major outbreaks with different material compositions.