Introduction
Resurgent calderas are the largest volcanic features on Earth. But they are not soaring mountains like composite volcanoes, nor hulking masses like shield volcanoes. They form by ground subsidence after especially large volcanic eruptions that partially empty the underlying magma reservoir causing its roof to collapse.
This type of caldera is truly immense and with diameters that can reach many tens of miles (kms) across. They erupt massive volumes of ash and pumice in eruptive columns that reach into the stratosphere. Ash from these eruptions is carried by winds across the globe. Caldera collapse is accompanied by the eruption of pyroclastic flows that cover huge areas both inside and outside the caldera walls.
The presence of resurgent domes are a defining feature of resurgent calderas. These uplifted areas form after caldera collapse when the ground surface is pushed up due to magma movement within the magma chamber. Resurgent domes are distinct from lava domes as they are uplift features, and not the products of volcanic eruptions themselves.
Resurgent calderas are marked by broad volcanic depressions ringed by low steep cliffs or hills that represent the walls of the caldera. Their floors may be relatively flat, particularly in areas where there are sediments from lakes that formed within the collapse basin. The interior of these calderas include resurgent domes and the products of post-caldera volcanism, which are typically either lava flows or lava domes.
Source: U.S. Department of the Interior, National Park Service
