Consisting of pumice, rock fragments, and small particles of volcanic glass, tephra is produced by explosive eruptions.
Tephra was generated in the eruption that created the cinder cone of Lava Butte, and the earlier phase of the Big Obsidian eruption that deposited windblown ash as far away as Idaho. At Newberry, cinder cone eruptions on the volcano's flank would produce relatively small volumes of tephra that would mostly accumulate close to the vent. Pumiceand ash eruptions from the caldera could send larger amounts of tephra to high altitudes where it could be blown by wind to populated regions and also become a hazard to aviation. Hot cinders and ashfall would likely ignite forest fires, and large volumes of gas would be released. Breathing ash particles and volcanic gases can irritate eyes and lungs and cause health issues.