Fifteen months after Mount St. Helens reawakened, the volcano is continuing to release massive amounts of lava in an unusual geologic display that in some respects confounds scientists.

Roughly every three seconds, a large dump truck load's worth of lava — 10 cubic yards — oozes into the mountain's crater. And with the sticky molten rock comes a steady drumfire of small earthquakes.

The unremitting, monthslong pace is not common, said U.S. Geological Survey geologist Dave Sherrod. Experts say it is unclear what the activity signifies or how long it will continue.

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