Eruption History and Volcanic Setting
Newberry is a shield volcano located in the United States, reaching an elevation of 2,434 meters above sea level. It is situated in a subduction zone tectonic setting on continental crust thicker than 25 kilometers. Official data from the Smithsonian Global Volcanism Program documents 11 confirmed eruptions in Newberry's geological record, spanning from approximately 9210 BCE to 690 CE.
Chronology of Historical Eruptions
The confirmed volcanic history of Newberry extends across ten millennia of the Holocene epoch. Isotopic radiocarbon dating places the earliest confirmed event around 9210 BCE (± 1200 years), centered along the south and east caldera rim. Subsequent activity occurred across several different zones, including northwestern rift structures and interior caldera locations.
During the 6th and 5th millennia BCE, multiple eruptions were recorded along the volcano's northwestern rift zones. An eruption around 5070 BCE (± 150 years) occurred in the lower NW rift zone (Lava Butte) and produced a Volcanic Explosivity Index (VEI) rating of 3. Another event around 4770 BCE (± 75 years) was recorded at Sugarpine Butte on the NW rift zone.
Later prehistoric activity includes a confirmed eruption around 1450 BCE located south of East Lake, established using obsidian hydration rind dating. The latest confirmed eruption recorded in the database occurred around 690 CE (± 100 years) along the south caldera wall. This 7th-century CE event reached a VEI of 4, the highest explosivity index assigned in Newberry's recorded record.
Representative Eruption Records
The table below presents representative records selected from the 11 total confirmed eruptions documented in the official catalog, illustrating recorded locations, scientific dating methods, and explosive magnitude ratings where assigned.
| Eruption Date | Activity Location | Dating Method | Volcanic Explosivity Index (VEI) |
|---|---|---|---|
| c. 9210 BCE (± 1200 yrs) | South and east caldera rim | Isotopic: 14C (calibrated) | Unassigned |
| c. 5070 BCE (± 150 yrs) | Lower NW rift zone (Lava Butte) | Isotopic: 14C (calibrated) | 3 |
| c. 4770 BCE (± 75 yrs) | NW rift zone (Sugarpine Butte) | Isotopic: 14C (calibrated) | Unassigned |
| c. 1450 BCE | South of East Lake | Chem/Bio: Hydration Rind | Unassigned |
| c. 690 CE (± 100 yrs) | South caldera wall | Isotopic: 14C (calibrated) | 4 |
Scientific Measurement and Eruption Dating
Documenting Newberry's eruptive timeline relies on specialized geological dating methods suitable for prehistoric volcanic material. Isotopic radiocarbon (14C) dating, calibrated for chronological precision, provides age estimates for carbonaceous material associated with eruptive deposits. Chemical and biological techniques, such as obsidian hydration rind analysis, provide additional age constraints for volcanic glass formed during eruptions.
The explosivity of recorded events is categorized using the Volcanic Explosivity Index (VEI), which evaluates erupted tephra volume and plume height on a logarithmic scale from 0 to 8. Out of the 11 confirmed eruptions, 6 have explicit VEI ratings in the database, peaking at VEI 4 for the 690 CE event along the south caldera wall.
Frequently asked questions
How many confirmed eruptions are recorded for Newberry?
According to official records from the Smithsonian Global Volcanism Program, Newberry has 11 confirmed eruptions recorded in its Holocene history.
When was the most recent confirmed eruption at Newberry?
The most recent confirmed eruption recorded in the official database began around 690 CE (± 100 years) along the south caldera wall.
What is the highest recorded Volcanic Explosivity Index (VEI) for Newberry?
The highest Volcanic Explosivity Index recorded for Newberry is VEI 4, which occurred during the eruption dated to around 690 CE.
Sources and further context
Official datasets support the event-specific facts.