Rainier (United States): Recorded Eruptions and Historical Activity

Mount Rainier is a stratovolcano located in the United States at a tectonic setting involving a subduction zone and continental crust over 25 kilometers thick. Standing at an elevation of 4,392 meters, the volcano has a documented history of volcanic activity comprising 20 confirmed eruptions recorded in the Smithsonian Global Volcanism Program database.

According to the official record, the earliest recorded eruption began around 8050 BCE, and the latest confirmed eruption occurred in 1450 CE. Across the entire catalog, 9 eruptions have associated Volcanic Explosivity Index (VEI) measurements, with the largest recorded VEI reaching 4.0.

Chronology of Recorded Eruptions

The historical activity of Mount Rainier spans multiple millennia, with activity documented across various centuries from the 81st century BCE through the 15th century CE. Researchers determine these dates and intervals using scientific evidence methods such as calibrated radiocarbon (14C) isotopic dating and tephrochronology tephra correlations.

Representative examples from the structured eruption record illustrate the methods and timing of historical events at the volcano:

• 8050 BCE (approximate): An early confirmed eruption occurred with a Volcanic Explosivity Index of 3.0, determined via calibrated radiocarbon isotopic evidence.
• 4850 BCE (approximate): A confirmed eruption took place with a Volcanic Explosivity Index of 2.0, also established through calibrated radiocarbon dating.
• 700 BCE (with a 50-year uncertainty window): A confirmed eruption documented via tephrochronology correlation.
• 250 BCE (with a 200-year uncertainty window): A larger confirmed eruption reached a Volcanic Explosivity Index of 4.0, supported by calibrated radiocarbon evidence.
• 1450 CE (with a 100-year uncertainty window): The latest recorded eruption period in the official database, established via calibrated radiocarbon dating.

Eruption Distribution by Century

The 20 confirmed eruptions are distributed across various centuries, reflecting intermittent periods of activity over thousands of years rather than continuous active behavior. The recorded distribution includes events in the following eras:

• 81st century BCE (1 eruption)
• 78th century BCE (1 eruption)
• 56th century BCE (1 eruption)
• 54th century BCE (1 eruption)
• 51st century BCE (1 eruption)
• 49th century BCE (1 eruption)
• 39th century BCE (1 eruption)
• 37th century BCE (1 eruption)
• 28th century BCE (1 eruption)
• 26th century BCE (1 eruption)
• 7th century BCE (3 eruptions)
• 5th century BCE (1 eruption)
• 4th century BCE (1 eruption)
• 3rd century BCE (1 eruption)
• 2nd century BCE (1 eruption)
• 5th century CE (1 eruption)
• 10th century CE (1 eruption)
• 15th century CE (1 eruption)