• High-explosivity events are often referred to as Plinian eruptions. They are named after Pliny the Younger, who described the eruption of Mount Vesuvius that destroyed the Roman city of Pompeii almost 2,000 years ago. During these eruptions, large amounts of magma are ejected into the atmosphere at high velocity — such as Mount St. Helens in 1980 and Mount Pinatubo in 1992.

The blast-fractured summit of Mount St. Helens dominates Clark County’s skyline to the north.

From other vantage points, the white-capped slopes of Mount Hood loom over the horizon to the southeast.

The two Cascade volcanoes have similar rock compositions, and the gases that are part of their eruptive phases are the same.

But Mount Hood is unlikely to adopt Mount St. Helens’ profile any time soon: The reason appears to be temperature.