COMMENT: Marty, Here in Alaska, we have been put on alert that Mt Spurr may erupt soon. Your computer has been remarkable projecting these trend of rising volcanic activity here in 2025 and we are still in the first quarter. Do you have any historical analysis of Mt. Spurr?
Rob
REPLY: Mount Spurr, a stratovolcano in Alaska’s Aleutian Arc, had no confirmed historical eruptions that have been documented in human records prior to its significant 1953 eruption. However, geological studies reveal prehistoric activity:
Holocene Eruptions:
The most recent major eruptive period occurred approximately 8,000–9,000 years ago, involving pyroclastic flows and lava dome formation that shaped the current structure of the volcano. These eruptions were identified through tephrochronology and radiocarbon dating of volcanic deposits.
Late Pleistocene Activity:
Evidence suggests earlier eruptions during the late Pleistocene, though precise dates are less well-constrained. These events contributed to the volcano’s formation and growth.
It is under watch right now for a possible eruption. Before 1953, Mount Spurr’s eruptions were prehistoric, with no written records or observations. Mount Spurr’s prehistoric eruptions are primarily studied through geology, but their ash layers provide valuable tools for archaeologists.
The 1953 eruption of Mount Spurr in Alaska was classified as a VEI 3 (Volcanic Explosivity Index 3) event. This eruption on July 9, 1953, produced a significant Plinian ash column reaching approximately 21 km (70,000 feet) in height. However, the volume of erupted material (tephra) was estimated at around 0.021 km³, placing it within the VEI 3 range (0.01–0.1 km³).
There were earthquakes in 2004 and debris flows by 2005. That was 51 years from 1953. Since this should be fractal, I would suspect there was probably a big one around 5200 years prior. This could be building to a big one above VEI 5 by 2031/2032. It should be coming alive here of the 72-year cycle from 1953 which brings us to 2025. We may still be looking at a VEI3 or VEI4 for that would leave the door open for a bigger one by 2031/2032.
For comparison, Mount Spurr’s 1992 eruption was rated VEI3/VEI 4, with a slightly higher tephra volume (-0.055 km³) and a plume height of 14 km. The distinction underscores that VEI considers both eruptive volume and secondary factors like plume height and eruption duration. The 1953 event, while explosive and impactful, did not meet the volume threshold for VEI 4.
Understanding the VEI
Each VEI level represents a tenfold increase in erupted material (e.g., VEI 4 is 10x larger than VEI 3). Higher VEI eruptions produce taller plumes, injecting ash and gases into the stratosphere (VEI 5+ can affect global climate). More significant eruptions (VEI 5+) are less frequent but more destructive.
VEI 7: Tambora (1815) ejected 160 km³ of material into the atmosphere, thereby reducing global temperatures by -3°C, known as the Year without a Summer in 1816.
VEI 6: Pinatubo (1991) released 10 km³, causing global cooling by -0.5°C.
VEI 5: Mount St. Helens (1980) erupted 1 km³, but did not alter the climate yet it was devastating 600 km²
