Volcanic mountains

Steam plumes are visible as volcanic activity increases at Mount Ruapehu Ski Resort, New Zealand

Steam plumes seen rising from Mount Ruapehu. 1 credit

Six weeks of increased seismic activity at Mount Ruapehu in New Zealand yesterday resulted in the strongest tremor in twenty years, sending plumes of steam into the air. Despite the increased activity, the volcano remains under a level two alert. There will likely be no eruptions or a minor eruption confined to the lake basin over the next four weeks.

In the past six weeks, Mount Ruapehu has exhibited the strongest volcanic tremor in two decades, along with an increase in the temperature of Crater Lake (Te Wai ā-moe). This period of increased volcanic unrest continues. Over the past week, the level of volcanic tremor has varied, with bursts of strong tremor interspersed with short periods of weaker tremor. This represents a change in character in the shake, and the driving processes remain unclear.

The past three days have seen Crater Lake’s temperature rise to 38°C after a four-week stint of 36-37°C. Our modeling suggests that to maintain lake temperature and a subtle increase, approximately 200-300 MW is required.

Due to intensified volcanic unrest, GNS Science personnel are conducting more frequent aerial gas measurements and sampling of Crater Lake. A gas measurement flight on April 28 recorded the sixth highest sulfur dioxide (SO2) flux of 390 tonnes per day since 2003. Sulfur dioxide is a strong indicator gas and is derived from a relatively shallow, which is perceived to currently exist a few miles below Crater Lake. Further gas flights will be conducted as weather conditions permit.

Geonet

mt ruapehu, new zealand, volcano
Crater Lake on May 3, 2022. Credit: Geonet

The steam plume was visible above Mount Ruapehu’s Crater Lake. The first sign of the plume occurred at about 9:45 a.m., and it slowly rose about 1 mile above the summit area, remaining visible until about 10:30 a.m.

Mount Ruapehu Ski Resort is one of the most unique resorts in the Southern Hemisphere. Its unique location is nestled among the jagged slopes of the highly active namesake volcano, Mount Ruapehu. The resort features exhilarating terrain made up of solidified lava, providing a unique skiing experience.

Located on New Zealand’s North Island, the volcano is the highest point on the island at 9,176 feet. The resort has two separate ski areas, Whakapapa and Tūroa, one located on the northern slope of the volcano and the other on the southwest slope. The resort is known for skiing in the winter but remains open during the summer and offers activities like hiking and sightseeing.

Mount Ruapehu Sky Waka
Sky Waka Gondola at Mount Ruapehu Ski Resort; image: henrymagazine.nz

As the resort’s summer season draws to a close and it prepares for ski season, Mount Ruapehu has something brewing beneath its crater. Recent signs of unrest have been reported in the form of tremors and rising temperatures at Crater Lake. Experts say this is concerning for a potential eruption and for the station. Mount Ruapehu is currently classified as a level two volcanic threat. Although an eruption may not be expected, constant signs of eruptive potential continue to be checked in.

What does this mean for Mount Ruapehu Ski Resort? This is not the first time the station has navigated Mount Ruapehu’s eruptive potential. In September 2007, while under a similar Level 2 Volcanic Alert, Mount Ruapehu erupted. The magma flooded the lahars that make up many tracks around the resort. Rocks, debris and hot ash filled the air and cluttered a nearly two-mile radius around the crater. Fortunately, there was no major damage or loss of life.

Although its namesake could potentially put a significant damper on the upcoming ski season, there is no immediate threat to the region. The resort will continue to offer summer activities, including hikes and gondola rides on the Sky Waka. The Skyline Walk, a scenic hiking trail, is closed to visitors due to the level two volcanic alert. Visitors are also recommended to avoid spending long periods of time in areas prone to hazards, including lahars.

If an eruption is detected by the Ruapehu Eruption Detection System (REDS), the resort has protocols to notify guests to clean sensitive areas. The REDS will send an automatic signal to the Whakapapa Ski Area Lahar Alert and Warning System (WLAWS) if seismic activity is detected. The WLAWS will then sound a siren and ask guests to take cover on higher ground and clear the area.

From now on, resort operations will continue to move forward. Summer activities and tourism will continue until the Volcanic Alert Level increases with potential eruption risks. The resort plans to open its two ski areas on July 7 and 8. In the meantime, the GNS and DOC will monitor Mount Ruapehu for lingering symptoms of impending eruptions.

Mount Ruapehu eruption
Mount Ruapehu’s most destructive eruption in 1996; image: fineartamerica.com