Endogenous processes and associated landforms

During February, the daily ground-tilt events stopped and gas emissions were barely detectable. The two arms of the Crater Glacier had by 30 May fully encircled the dome.

Further down slope glacier ice descended into the gullies that had been carved by erosion into the Pumice Plain. Radar imagery analyzed by Jet Propulsion Laboratory staff during late March showed that the E and W arms of Crater Glacier were touching, or close to touching, just N of the s lava dome.

No tilt changes were associated with the swarm. During Marchthe most significant developments were a small, M 2. This report spans 28 November through October As of Octoberearthquakes, volcanic gas emissions, and ground deformation had all fallen to levels observed prior to the onset of the eruption.

On 25 Januarya steam plume rose from the dome slightly above the crater rim. Geological Survey, Professional Paperp. Though seismicity had persisted at low levels through mid-Februaryvery few earthquakes were recorded after late January. Geological Survey Open-File Report22 p. Ground tilt measurements showed an overall subsidence in the area of the new dome.

On 31 December aerial observers saw a new small, snow-free spine on top of the active lobe. Helens crater encircled by ice, as seen from the NW. Cite this Report Eruption ceased in late January ; quiet continues in late The eruptive episode that began with the volcano reawakening in October BGVN Sherrod and others provide a comprehensive discussion of the portion of the eruption.

Weekly Reports - Index. Aerial view of the St. On 14 March, the Pacific Northwest Seismic Network recorded four very small earthquakes located near the volcano. The latter started with a roughly M 1. By 8 July, the old and new lava domes in the crater were encircled by ice figure There were no tilt changes associated with this activity.

Old and new lava domes center and upper right respectively in the St.

Comparison of photographs taken by remote cameras during late January to mid-February showed no evidence of extrusion. Locatable earthquakes were fewer than one per day, all under M 2.

A GPS receiver on the previously active spine settled about 2 cm per day on a southward path.

Helens crater, as seen from the N.Figure Aerial view of the St. Helens crater, as seen from the N. The two arms of the Crater Glacier had by 30 May fully encircled the dome.

Endogenous processes and associated landforms
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