Mount St Helens Survey 2026

On the summit

Eric and Parthiv

Oct 1, 9am – 6pm.

Results: St Helens has eroded down 0.4ft since late Sept 2025 and the summit has moved 4.7ft to the east. It is still the 102nd highest peak in WA.

Survey equipment set up

Mt St Helens has been losing elevation regularly since 1989, likely due to erosion off the steep north face. The loss has been highly linear, at 0.3ft/year (R squared value 0.98). It was measured by USGS in 1989 using stanadard triangulation methods, then by LiDAR in 2002, 2009, 2017, and 2018. I’ve taken GNSS measurements in early fall in 2023, 2024, 2025, and 2026, and as far as I know these have been the only GNSS measurements of the summit. I survey in late fall to be at the end of the erosion season just before seasonal snow covers the summit and freezes all the rock together.

Snowman nearby

Parthiv and I got last-minute permits and headed out of town around 5am, then were hiking up from the Climbers Bivouac trailhead by 9am. We made good time up, and reached the summit by early afternoon. It looked different than I remembered, which is consistent with it eroding down. I used my surveyors hand level to determine the highest rock, which was on the edge of the cliff. It was too windy to mount the 2m antenna rod, so I mounted the 1.0ft rod with the tripod and put a Trimble DA2 GNSS receiver on to log data.

We hung out for 2 hours logging data (this is the minimum time required for standard OPUS Static processing). We then packed up, hustled down by sunset and drove back home.

Results: St. Helens shrunk by 0.4ft compared to Sept 27, 2025, and the summit location shifted 4.7ft to the east. The current elevation in the modern vertical datum is 8325.0ft +/-0.1ft NAVD88. Note: this is a different datum than the USGS quads use, which is NGVD29, but NAVD88 is the modern standard so I am reporting in that datum now.