Expedition to Tofua Volcano, Tonga

We’ve just recently returned from a major expedition to the Kingdom of Tonga and in the process helped uncover the world’s 9th lava lake.

Several years back, I acquired grainy satellite imagery of Tofua, a remote volcanic island in Tonga. Every image revealed thermal anomalies within the volcano’s active Lofia Cone – anomalies that persisted for months. This led me to theorise that molten lava was present, potentially forming an active lava lake.

I managed to obtain photographs from a rare expedition by passing sailors who had visited the crater. Their images captured active vents and minor strombolian eruptions, but disappointingly, no lava lake. While this tempered my initial excitement, I was grateful for the clarity these observations provided.

However, recent developments reignited my interest. Thermal anomalies became more frequent and recorded significantly higher megawatt readings. Even more compelling, high-resolution true-color satellite imagery began showing what appeared to be lava pooling within the crater. The volcanic system seemed to be evolving.

Yet satellite data, however sophisticated, could only tell part of the story. To definitively confirm the presence of a lava lake, direct observation would be necessary, which meant planning an expedition to this remote volcanic island.

Planning the expedition required over a year of preparation and presented enormous logistical hurdles from the beginning. Tofua is one of the world’s most remote volcanic islands, located in the vast expanse of the Pacific Ocean. So we assembled an international team of experts with specialised skill sets and a plan was born. The team included a doctor and a meteorologist, who provided up-to-date weather forecasts to ensure a safe journey to and from the island.

Our first mission was to transport the team and all our gear to the Ha’apai island chain in Tonga. For team members traveling from Europe, this involved five separate flights. I had a much easier journey, with a single direct flight from Auckland, New Zealand, to Nuku’alofa and then onto Ha’apai.

Landing at Nuku’alofa

The next morning, we headed to the domestic airport and boarded a small Twin Otter aircraft operated by Lulutai Airlines, bound for Ha’apai.

We had allocated five days to reach Tofua, anticipating that the weather could be bad. While the weather in Nuku’alofa had been poor, conditions in Ha’apai were good, so we decided to sail on the same day we arrived, wasting no time.

Our first priority was finding water. Although there is a freshwater lake near Tofua’s summit, we weren’t sure if it was acidic or safe to drink. To be safe, we bought one hundred bottles of water, unsure of how long we would be on the island or when we would find a safe window to return. We also brought a large supply of food.

We made our way to the beach where our boat was waiting. Our skipper, an ex-Tongan Navy veteran, had been sailing these waters for over forty years. We were relieved to see a small zodiac attached to the roof of the boat, which would make ferrying our gear and ourselves to shore much easier. And so, with over a thousand liters of fuel on board, we lifted anchor and began our journey to Tofua.

The boat trip began with excitement, but as the hours passed, most of us were ready to get off. The rolling waves slowed our progress, and soon we found ourselves in the vastness of the Pacific Ocean with no land in sight. At one point, we were treated to a sighting of whales and dolphins.

Fotuha’a Island marked the halfway point of our journey. Despite appearing uninhabited, the island has a population of over 100 people. It featured many interesting sea caves, including a massive sea arch. Although we would have loved to stop and explore, we had to keep moving.

Just past Fotuha’a, we finally caught our first glimpse of Tofua and the nearby island of Kao. A plume of smoke was rising, confirming that Tofua was active. The hours continued to pass, but the island still seemed an eternity away.

More hours passed, but finally we were in the straight between Tofua and Kao.

The island of Kao, a stratovolcano reaching a height of 1,030 meters, making it the highest point in all of Tonga. Despite its volcanic origin, the island shows little sign of significant erosion, such as deep gullies or high sea cliffs, suggesting it is geologically young. The last major eruption date is unknown, but the volcano is considered dormant rather than extinct.

The massive underwater eruption of the Hunga Tonga-Hunga Ha’apai volcano (January 2022), triggered a powerful tsunami that caused significant coastal erosion across Tofua.

Sea caves along the coast of Tofua, begging to be explored. I need to come back with a kayak next time…

Before we departed, we spent a significant amount of time studying satellite images to find the best landing spot. After consulting with our skipper, we agreed on a location on the northern side of the island. He couldn’t get the main boat too close due to reefs and other hazards, so we used the smaller zodiac to ferry everyone and all the gear ashore. I made the first trip, securing a rope between the boat and the island, which made the subsequent back-and-forth trips much faster.

After getting everyone and all the gear onto the island, we said goodbye to our skipper, who was off to spend a few days fishing. It was a surreal feeling to be left alone on a very remote, uninhabited island.

We were immediately faced with an epic battle against the jungle. We had specifically landed on the northern side to avoid the densest areas, but the jungle here was still fierce and nearly impenetrable. It took us an hour just to move 50 meters. The vegetation was incredibly thick, and with no tracks or maps, we also had cliffs to navigate. The challenge was made much harder by the hundreds of kilograms of gear we had to carry. As daylight began to fade, we decided to set up camp right there in the jungle.

Just before we went to bed, we noticed the sky above the trees was glowing orange. We were excited, knowing that there was lava somewhere near the summit.

It was a rough night. We hadn’t planned to camp in the jungle, and we were surrounded by a lot of nasty creepy-crawlies. Throughout the night, we heard things crashing through the undergrowth, which we suspected were feral pigs.

The next morning, we rose early, determined to reach the summit. We spent hours pushing through the jungle, hoping to find a clearer path. Our satellite images suggested the area would open up, but instead, we found ourselves battling through a dense wall of two-meter-high ferns, bracken, and stinging nettle. It was a miserable and difficult climb. Adding to the challenge, the heat and humidity were relentless, and the ground became progressively steeper. Our progress was painfully slow.

After hours of slogging through the difficult terrain, we finally reached the summit and got our first glimpse into the caldera. It was a great moment. Right in front of us was the Lofia cone, billowing a bluish gas – a sure sign of sulfur dioxide. With no time to waste, we immediately began our descent into the caldera. Getting down, however, proved to be extremely difficult. The slope was incredibly steep with very little to hold onto.

After a lot of slipping and sliding, we finally made it down into the caldera. From there, it was only about a one-kilometer walk to the Lofia cone. The first things we noticed were the massive erosion fractures and gullies that required careful navigation. Secondly, the ground itself was unstable, with many hollows and holes to avoid. We investigated some of the holes and couldn’t even see the bottom.

As we got closer, we could hear the volcano rumbling. More concerning, however, were the lava bombs scattered all around us. Many were fresh, with some still hot to the touch. This was clear evidence that Tofua is not a quiet volcano; it erupts regularly, sending massive, fridge-sized lava bombs flying high into the air. We had to be careful.

Lava bomb and impact crater

Upon closer approach, the ground was almost entirely covered in lava bombs. This forced us to limit our time in this extremely hazardous area. Eventually, we reached the edge of the central cone and found ourselves peering down into a vast, deep crater. We were immediately struck by how much the crater had changed from previous photographs we had seen; it was now far deeper, which is strong evidence of recent and powerful eruptions. Although we couldn’t see any molten lava at that moment, the crater’s rough, dark texture was a clear product of basaltic lava flows and tephra. The lighter, reddish-brown hues on the inner walls were likely the result of hydrothermal alteration or the oxidation of iron within the volcanic rock. A plume also rose, likely composed primarily of water vapor and sulfur dioxide.

As we were taking photos, a sudden boom and rumble made us panic. Luckily we didn’t see any lava bombs. We quickly retreated and made our way to safe ground. It was time to get the drones out and see if we could spot any lava! And it didn’t take long….

The gas cleared, and we got our first view: a churning lake of lava, about the size of a tennis court, at the bottom of the crater.

Can you spot us?

While the exact number of lava lakes may be debated, there are only a handful of persistent ones in the world, making their existence incredibly rare. The count is fluid, with some sources listing as few as five or six, while others go up to eight or nine, depending on whether the lava lake is considered persistent or temporary. For instance, the lava lake on Mount Michael was confirmed only a few years ago, and became officially the worlds 8th. Regardless of the exact number, the sighting of a lava lake is a privilege, given how few volcanoes on Earth can sustain these phenomena.

As it was beginning to get dark, we made our way out of the caldera and set up camp right on the caldera rim. We had a great view down inside the caldera. As the sun went down, we noticed Lofia was glowing orange. It got brighter and brighter, lighting up the sky around it also. I also managed to get some shows of the lava lake at night.

Looking back, the expedition to Tofua was a hell of a trip. Despite the grueling travel, the brutal jungle climb, and the constant fear of being on an active volcano, our team made it. The moment we finally peered into the caldera and saw that churning lava lake in the Lofia cone was something I’ll never forget. Watching that crater glow in the darkness, surrounded by that raw, untamed landscape, was the perfect and unforgettable end to a wonderful expedition.