Mount Ruapehu

Our gallery presents an infrared GAC image (Channel 3) of the New Zealand area acquired at 0310 UTC on June 17, 1996 from NOAA 14. The ash plume from erupting Ruapehu shows up as a feather-shaped dark plume aligned northeastward from the North Island. In this case, no split-imaging techniques were required to display the plume because it was so much warmer than its surroundings. Mount Ruapehu had erupted approximately 8 hours earlier (1900 UTC June 16 or 0700 June 17 LST), and at the time of the image, eruption pulses timed every 10-15 minutes were sending ash several kilometers above the volcano's summit. Being the start of winter in the Southern Hemisphere, snow is easily seen on the Southern Alps of the South Island.

At 2797 meters, Mount Ruapehu is the highest mountain on New Zealand's North Island, and is the country's largest cone volcano. It is one of three volcanoes forming the central massif (the other two being Ngauruhoe and Tongariro). The Maori name may be translated as "Explosion Pit." Ruapehu is not far from the Taupo Volcano, which 1600 years ago blew up in the world's most violent volcanic explosion within the past 5000 years.

Mount Ruapehu, located 13 km south southwest of Ngauruhoe, has been the scene of numerous eruptions in the past. Following the appearance of steam plumes in March, 1945, an eruption spread ash clouds over the entire North Island on August 21-22. In 1953, a release of water from Crater Lake atop the volcano caused a lahar (flow of volcanic mud and debris), which swept down the Whangaehu River, weakening a railroad bridge. One fifty one deaths resulted when the bridge collapsed under the weight of a train trying to cross the weakened structure. A warning system now exists to avoid a repeat of this type of catastrophe.

In September - October, 1995, earthquakes preceded a significant eruption of the volcano. On March 26, 1996, a small island was observed in Crater Lake and the temperature of the lake had risen to 50 degrees C. Between 1430 LST on June 15 and 0100 LST June 16, volcanic tremors reached the highest levels recorded in the past six months. The earthquakes plateaued at levels similar to those recorded during the October 11-12, 1995 eruptions, and between 0650 LST and 0835 LST June 17, 1996, eruption pulses pushed ash to several kilometers high. Ash fell as far north as Turangi and a small lahar swept down the Whangaehu River valley. By 1500 LST (the time of the image), eruption pulses were occurring every 10-15 minutes. By 21-2200 LST on June 17, sprays of glowing rocks were being ejected above the crater, and an ash plume extended 1000-2000 meters above the summit. Crater Lake was destroyed and the crater floor was dry.

NOAA's National Environmental Satellite, Data, and Information Service's Satellite Analysis Branch issued nine Volcanic Hazards Alert messages. Six Volcanic ASH Forecast Transport and Dispersion (VAFTAD) model products were sent to the FAA as ash drifted northeastward toward the island of Tahiti on June 17-18. Using bispectral techniques similar to those used to produce GOES images which best show volcanic ash, ash was detected in all NOAA-12 and NOAA-14 passes on June 17.

By June 20, 1996 the crater had a flat floor at about 120-150 meters deep below the pre-1995 lake overflow level. Due to intense monitoring and an excellent warning system, no fatalities have occurred in this most recent eruption of Mount Ruapehu, the volcano which has produced more historic eruptions than any other crater lake in the world.