Landsat Image Gallery
acquired April 23, 2022

First Stop: Tofua  

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

With few protective fringing reefs around the island, sandy beaches are scarce, and landings by boat require careful navigation to avoid cliffs and craggy volcanic formations along the coasts. Once on land, traveling anywhere is grueling due to dense semi-tropical forests that blanket much of the island’s steep terrain. There is little permanent freshwater, aside from the difficult-to-reach caldera lake at the island’s center. And there’s the looming threat that Lofia—an often steaming volcanic cone to the north of Tofua’s lake—could erupt explosively, much like 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 plume of water vapor and other volcanic gases drifted above the crater over young lava flows and ash deposits north of the lake. Geologic evidence suggests that Tofua has erupted at least 12 times since 1774, with the most recent eruption starting in 2015 and continuing to the present.

Volcanologists monitor Tofua for new activity by using thermal sensors on a variety of NASA, NOAA, and European Space Agency satellites. For instance, 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 Services reported that elevated 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 of the HMS Bounty. Half of Bligh’s crew famously mutinied during an expedition to Tahiti to collect breadfruit plants. The bloodless rebellion occurred about 50 kilometers (30 miles) south of Tofua, with Bligh and the other loyalists left adrift on the open seas with just four cutlasses, a handful of tools, and a few days’ worth of food.

Bligh ultimately 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 some 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 some 80 kilometers to the south. After that attack, Bligh and his men fled to Kupang, a Dutch settlement some 6,500 kilometers to the west.

More than two centuries later, Tofua is mostly undeveloped and stands as 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.

Still, the human fingerprint on the island is widespread. Human-ignited fires have altered forests across much of the island and left secondary forests and brushlands in their place in some areas, according to a report from the South Pacific Biodiversity Conservation Program. The authors also note that the introduction of feral dogs, cats, pigs, rats—and more than 200 non-native plants—has significantly altered the island’s ecosystems.

People have also cleared patches of forest (visible on the left side of the image) to raise kava (Piper methysticum) on the island’s fertile volcanic soil. The plant’s roots are processed into a powder that is used to make a tea said to have calming, anesthetic, and euphoriant effects similar to those caused by alcohol.

 

NASA Earth Observatory image by Lauren Dauphin, using Landsat data from the U.S. Geological Survey. Story by Adam Voiland.

This image record originally appeared on the Earth Observatory. Click here to view the full, original record.