Changes in Crater Morphology Associated With Volcanic Activity at Telica Volcano, Nicaragua

Volcanic summit craters are typically noted to form by roof collapse into a depressurized magma chamber or by explosive excavation. Recent examples of effusive activity (e.g., Kilauea Volcano, Hawai'i) allowed specifically for quantification of the collapse process. However, small spatiotemporal morphologic change related to background mass wasting and low-level explosive activity has not been well quantified in volcanic craters. Telica volcano, Nicaragua, is a persistently restless basaltic-andesite stratovolcano. Telica's persistent restlessness is caused by a long-lived magmatic-hydrothermal system with high-temperature crater fumaroles and low-frequency seismicity, punctuated by subdecadal, low-explosivity (VEI 1–2) phreatic eruptions. We use photographic observations (1994 to 2017) and structure-from-motion point cloud construction and differencing (2011 to 2017) to analyze changes at Telica in the context of summit crater formation and eruptive precursors. Crater wall retreat (up to 40 m) spatially correlates with long-lived high-temperature fumaroles in the crater walls, whereas eruptions eject material (>5 m) from the crater floor through vent formation and/or clearing. These processes sustain a morphology similar to that of pit craters but without a shallow depressurized magma chamber. Our observations indicate system-wide sealing prior to eruption by viscous magma in the conduit and eruption of a dome in 2017 and hydrothermal mineralization, not from vent covering talus; though, vent covering talus can redirect the shallow conduit. This study shows promise for photogrammetric techniques in correlating morphologic change with summit crater formation and volcanic activity and the power of long-term visual observations in understanding active volcanic processes.