Okmok is a shield volcano located in the United States, standing at an elevation of 1,073 meters within a subduction zone setting characterized by intermediate crust (15-25 km). According to official records from the Smithsonian Global Volcanism Program, the volcano has a confirmed total of 18 eruptions spanning thousands of years, with activity ranging from prehistoric isotopic dates to modern historical observations.
Overview of Recorded Activity and Eruption History
The historical and prehistoric record for Okmok captures significant explosive events and caldera-forming activity. The earliest recorded eruption in the official collection dates back to 6310 BCE with an uncalibrated radiocarbon evidence method and an estimated start year uncertainty of 500 years. Another major prehistoric event occurred around 100 BCE (with a 50-year start year uncertainty) in the Okmok II caldera area, reaching a Volcanic Explosivity Index (VEI) of 6.0, which stands as the largest recorded VEI for this volcano.
In total, the official record includes 15 eruptions with documented VEI observations out of the 18 confirmed events. Historical reporting of activity picks up more precisely in the 19th and 20th centuries. For instance, an eruption took place from July 2, 1824, to July 2, 1830, around Cone B?, and later activity occurred in the southwest part of the caldera at Cone A starting on July 2, 1938.
Recent Activity
The most recent confirmed eruption in the database started on July 12, 2008, on the northeast caldera floor and concluded on August 19, 2008, reaching a VEI of 4.0. The profile's last known eruption year is recorded as 2008, and the latest confirmed eruption date in the structured record is July 12, 2008. Official records do not indicate that any eruption is continuing.
Distribution of Eruptions by Century
The recorded eruptions are distributed unevenly across different centuries and eras:
- 64th century BCE: 1 eruption
- 1st century BCE: 1 eruption
- 19th century CE: 5 eruptions
- 20th century CE: 10 eruptions
- 21st century CE: 1 eruption
Frequently asked questions
Where is Okmok located?
Okmok is located in the United States.
What type of volcano is Okmok?
Okmok is classified as a shield volcano.
How many eruptions has Okmok had?
The Smithsonian Global Volcanism Program records 18 confirmed eruptions for Okmok.
What is the largest recorded VEI for Okmok?
The largest recorded Volcanic Explosivity Index (VEI) for Okmok is 6.0.
When was Okmok's latest eruption?
The latest confirmed eruption occurred in 2008, beginning on July 12, 2008, and ending on August 19, 2008.
Sources and further context
Official datasets support the event-specific facts.