The level of seismic activity has continued at a low level over the last 24 hours. Those signals recorded were dominantly of the long-period type, with 20 noted on stations in addition to Chances Peak, which has many more signals due to its close proximity to the actively growing dome. No volcano-tectonic earthquakes were recorded during this period. Long-period earthquakes are often associated with the upward movement of molten rock at active volcanoes and similar signals are also recorded when rock falls occur from the lava dome. The low number of long-period earthquakes indicates that molten rock (or magma) has a free pathway upwards.
The eastern and southern EDM triangles were measured today. EDM (Electronic Distance Metre) measurements provide an indication to scientists about very small-scale swelling or contraction of the volcano which may accompany changes in the state of activity. Both of these EDM triangles again indicated today that very minor changes are occurring on a daily basis, with line lengths shortening by about 1 mm per day. Scientists currently interpret these movements as an indication of slight contraction of the volcano in response to the slow movement of molten rock to the surface.
Visual observations were not made from the air today due to a technical problem with the helicopter, which is being fixed over the weekend. Measurements of the high point on the dome indicate that it has lowered by a few feet since last week, probably due to rock falls from it. Several spines visible from the east continue to grow, and the main focus of activity is currently on the eastern side of the dome, although relatively few rock falls are occurring at present. One spine had a measured vertical growth of about 7 m (23 ft) over the past 24 hours. The growth of lava domes is often sporadic, and we should expect the low growth rate of this week to increase again sometime in the future.