First stop: Tofua

Compared to the low-lying sand and coral islands that make up most of Tonga’s Ha’apai archipelago, Tofua stands out. The high, cone-shaped volcanic island is difficult to access and comparatively inhospitable.

Because there are few protective fringing reefs around the island, sandy beaches are rare and boat landings require careful navigation to avoid cliffs and rugged volcanic formations along the shores. Once on land, getting anywhere is strenuous, as dense semi-tropical forests cover much of the island’s steep terrain. Apart from the difficult-to-access Caldera Lake in the center of the island, there is hardly any permanent fresh water. And there is the looming threat that Lofia – an often steaming volcanic cone north of Lake Tofua – could erupt explosively, similar to what Hunga Tonga-Hunga Ha’apai, its volcanic neighbor to the south, did in 2022.

The OLI-2 (Operational Land Imager-2) on Landsat 9 captured this image of the island on April 23, 2022. A cloud of water vapor and other volcanic gases drifted above the crater over young lava flows and ash deposits north of the lake. Geological evidence suggests that Tofua has erupted at least twelve times since 1774, with the most recent eruption beginning in 2015 and continuing to this day.

Volcanologists monitor Tofua for new activity using thermal sensors on various NASA, NOAA and European Space Agency satellites. For example, the Global Volcanism Program at the National Museum of Natural History reported that the VIIRS (Visible Infrared Imaging Radiometer Suite) on the NOAA-NASA Suomi NPP satellite detected thermal anomalies on 29 days between February and July 2023. In May 2024, Tonga Geological Survey reported that increased thermal activity had returned to normal levels.

One of Tofua’s most famous visitors – British Royal Navy officer William Bligh – arrived in April 1789 on a 7-meter (23-foot) utility boat with 18 crew members from the HMS Bounty. Half of Bligh’s crew mutinied during an expedition to Tahiti to collect breadfruit plants. The bloodless rebellion occurred about 50 kilometers (30 miles) south of Tofua, leaving Bligh and the other loyalists on the open sea with just four cutlasses, a handful of tools and a few days’ worth of food.

Bligh eventually planned to head for the nearby island of Tongatapu, but his first stop was Tofua. The hope was to gather food and water, but aside from a few coconuts, the men found little of either. One of Bligh’s men was stoned to death by a hostile group of people from Nomuka, another Ha’apai island about 50 miles (80 kilometers) to the south. After this attack, Bligh and his men fled to Kupang, a Dutch settlement about 6,500 kilometers west.

More than two centuries later, Tofua is largely undeveloped and is considered an oasis of biodiversity. Hundreds of plant species thrive on the island and a variety of small mammals, reptiles and birds live there, including swifts, starlings, honeyeaters, rails, ducks and pigeons.

Nevertheless, the human fingerprint is widespread on the island. According to a report from the South Pacific Biodiversity Conservation Program, human-caused fires have altered forests across much of the island, leaving behind secondary forests and scrubland in some areas. The authors also note that the introduction of feral dogs, cats, pigs and rats – and more than 200 non-native plants – has significantly altered the island’s ecosystems.

People have also cut down patches of forest (visible on the left side of the image) to grow kava (Piper methysticum) on the island’s fertile volcanic soil. The roots of the plant are processed into a powder that is used to make a tea that is said to have a calming, numbing, and euphoric effect similar to that of alcohol.

NASA Earth Observatory image by Lauren Dauphin using US Geological Survey Landsat data. Story by Adam Voiland.