California’s Lassen Peak Volcano is Sinking and Volcanologists Don’t Know Why

California’s Lassen Peak is sinking at a rate of about a centimeter per year for the past three decades.

But volcanologists can’t figure out why.

With no explosion in over a century, it might appear that California’s Lassen Peak hasn’t changed much. But recent findings show the volcano has been slowly sinking for the past three decades. And volcanologists can’t figure out why.

A recent study shows that there was a broad range of sinking measuring about 18 to 24 miles and progressing at the rate of about a centimeter per year on the peak.

The scientists believe that this slow sinkage of Lassen Peak has been going on since the 1980s. They believe the source of the sinking is a point located about 5 miles beneath the volcano’s center.

Speculations about the volcano sinking are:

Cooling and crystallizing of magma after the 1914-17 eruptions of Lassen Peak. As magma cools, it loses volume, so any new magma that triggers the eruption over 100 years ago may be slowly losing volume.
Change in the flow of water heated by magma underneath the volcano.

While there are many possible explanations for the sinking of Lassen Peak, the researchers are relyon their regional GPS measurements to understanding the role of crustal extension plus other hydrothermal/magmatic processes in deformation during recent decades.