Extrusion rate of the Mount St. Helens lava dome estimated from terrestrial imagery, November 2004-December 2005

Oblique, terrestrial imagery from a single, fixed-position
camera was used to estimate linear extrusion rates during
sustained exogenous growth of the Mount St. Helens lava
dome from November 2004 through December 2005. During
that 14-month period, extrusion rates declined logarithmically
from about 8-10 m/d to about 2 m/d. The overall ebbing of
effusive output was punctuated, however, by episodes of fluctuating extrusion rates that varied on scales of days to weeks.
The overall decline of effusive output and finer scale rate
fluctuations correlated approximately with trends in seismicity
and deformation. Those correlations portray an extrusion that
underwent episodic, broad-scale stick-slip behavior superposed on the finer scale, smaller magnitude stick-slip behavior
that has been hypothesized by other researchers to correlate
with repetitive, nearly periodic shallow earthquakes.