Echo Crater, which holds Frying Pan Lake, was ripped open during the 1886 Mount Tarawera eruption - the same event that destroyed the Pink and White Terraces at nearby Lake Rotomahana. That eruption split a 17-kilometre rift from Mount Tarawera southwestward, carving several craters along the way. Echo Crater was one of them.

Rainwater and heated groundwater began pooling in the crater floor, but the lake as it exists today did not take shape until after a second eruption on 1 April 1917. That blast enlarged the crater enough for hot springs to fill it to its current extent by mid-1918. It also resculpted Cathedral Rocks, the massive rhyolitic formation on the lake's northern shore - rock at least 60,000 years old, renamed from its original title of Gibraltar Rock after the eruption completely altered its profile. A fumarole called the Devil's Blowhole, once a feature of the crater's northern wall, vanished in the same event.

Frying Pan Lake manages to be acidic overall - averaging pH 3.8 - despite being fed by alkaline springs on its bed that reach pH 8.2 to 8.7. The contradiction creates gradients: zones where acidity shifts sharply over short distances, each supporting different organisms. Blue-green algae Mastigocladus laminosus colonize the more acidic patches, while the eukaryotic Cyanidium caldarium favours conditions closer to the alkaline inputs. The lake is a laboratory of extremophile ecology, where the chemistry of the water determines what can survive and where.

The most recent eruption within Echo Crater occurred on 22 February 1973, destroying the Trinity Terrace area along the southeastern shore. Colourful sinter terraces still cling to the western shoreline - mineral deposits laid down by geothermally heated water, slowly building new geological features while the old ones are periodically erased.

Frying Pan Lake breathes on a schedule that nobody fully understands. Its water level and outflow volume follow a repeating cycle of roughly 38 days, locked in an inverse relationship with neighbouring Inferno Crater Lake. When Inferno's water level and temperature rise, Frying Pan's level drops and its outflow decreases. When Inferno subsides, Frying Pan swells. The two lakes share underground plumbing, but the mechanism driving this oscillation remains one of the Waimangu Valley's enduring puzzles.

The outflow has diminished over the decades - from over 122 litres per second in 1970 to around 100 litres per second by 2014. Within each 38-day cycle, the flow varies by as much as 20 litres per second. The hot water drains into Waimangu Stream, a scalding creek that carries the lake's acidic discharge downstream.

Frying Pan Lake is one of the first major features along the main Waimangu walking track, which follows the rift valley through a landscape where geothermal activity is not a curiosity but the dominant fact. Near the lake's northeastern shore lies the site of the extinct Waimangu Geyser, which between 1900 and 1904 erupted to heights of 460 metres - the tallest geyser eruptions ever recorded. It killed four people in 1903 when visitors ventured too close.

The walk passes Cathedral Rocks with their trailing steam, the sinter terraces with their mineral colours, and the lake itself - a flat expanse of grey-green water that seems to simmer beneath its permanent cloud of vapour. There are no fences at the water's edge in many places. The heat radiating from the surface is its own warning.