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.

中文翻译：

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尼加拉瓜的特里卡火山的火山口形态与火山活动的关系

通常注意到火​​山顶坑是由屋顶坍塌进入减压岩浆室或通过爆炸性挖掘形成的。涌动活动的最新例子（例如，基拉韦厄火山，夏威夷）专门用于量化崩溃过程。但是，与火山口背景消沉和低水平爆炸活动有关的小时空形态变化尚未得到很好的量化。尼加拉瓜的特里卡火山是一个持续不安的玄武岩-安山岩平流层火山。Telica持续的躁动是由长期存在的岩浆热液系统引起的，该系统具有高温的火山口喷气孔和低频地震活动，并伴有年代际低爆炸性（VEI 1-2）的潜水爆发。我们使用摄影观测结果（1994年至2017年）以及从运动点云的构造和差异化（2011年至2017年）来分析特里卡峰顶火山口形成和喷发前体的变化。火山口壁的后退（最大40 m）在空间上与火山口壁中长寿命的高温喷气孔在空间上相关，而火山喷发通过火山口的形成和/或清除从火山口底部喷出物质（> 5 m）。这些过程维持类似于坑坑的形态，但没有浅的减压岩浆腔。我们的观察结果表明，在管道中的粘性岩浆喷发之前的全系统密封以及2017年穹顶的喷发和热液矿化（而不是从喷口覆盖的距骨）是全系统的; 但是，排气孔覆盖距骨可以改变浅导管的方向。