On January 15, 2022, the island nation of Tonga was rocked by a monumental eruption of the Hunga Tonga-Hunga Ha’apai volcano. The immensely powerful explosion could be heard from New Zealand to Alaska, and it sent tsunami waves across the entire Pacific basin. Waves of over 3 feet (0.9m) were recorded in Alaska, while two people were reported to have died along the coast of Peru and two injured in Japan due to the effect of tsunami. Three people have died in Tonga, but estimation of casualties and damage are very rudimentary on the islands near Hunga Tonga-Hunga Ha’pai because of near-complete loss of internet and ability to communicate.
The eruption also flung a massive amount of ash, gas, and steam high into the stratosphere, creating an umbrella-like cloud that spread across the region. Data collected on January16 by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission, shows ash and gas from the eruption rising to an altitude of 31 kilometers (19 miles). CALIPSO is a joint mission of NASA and France’s National Centre for Space Studies (CNES).
The thick ash has created substantial aviation hazards. It has delayed reconnaissance flights aimed at assessing damage of Tonga’s islands as well as largely obscured the islands from satellite view. Although limited, imagery and overflights reveal a very thick layer of ash lying atop nearby islands as well as structural damage affecting coastal towns on several of Tonga’s islands. The large amount of ash raises health concerns, including potential respiratory problems and contamination of wells used for drinking water. Volcanoes often emit sulfur dioxide, a substance that can cause severe respiratory distress in both people and animals.
Since the January 15 eruption, the volcanic ash and gas has not stayed stationary, but has spread over the region. By January 16, a thick blanket of ash and gas reached Australia, where it continues to spread. On January 17, The Moderate Resolution Imaging Spectroradiometer (MODIS) on board NASA’s Terra satellite acquired a true-color image of volcanic ash blanketing the Coral Sea as well as Queensland and Northern Territory, Australia. Even though the ash cloud had travelled more than 5,000 km (3,100 miles), it was still so thick that it obscured the land from view in many locations.
The bright white streak of cloud seen over the Gulf of Carpentaria and Papua New Guinea is not caused by ash. It is part of an optical phenomenon known as sunglint. This occurs when sunlight reflects off the surface at the same angle that a satellite sensor views it. The result is a mirror-like reflection of sunlight off the water or cloud and back at the satellite sensor. Sunglint is often seen as a silver color in water but, in this case, the sunlight reflects strongly from the cloud to create a bright white streak.