Steamy Earth
The North Island of New Zealand is well known for its scattering of geothermal hot pools, the highest temperatures in these are reached largely within the Taupo Volcanic Zone. The most renowned area of geothermal bathing is the Pink and White Terraces which gained the status of the 8th Wonder of the World in Victorian times, before being buried in the eruption of Mount Tarawera in 1886. At the time it was thought to be the largest silica sinter deposit on Earth. Despite the eruption, small areas of the terraces have been rediscovered underwater in Lake Rotomahana. Walking through the Waimangu Valley towards Rotomahana, steams rises from milky blue craters, pink clays and swirls of brightly coloured algae. It is no surprise that super-heated water and earth leads to speciation and provides refugia for plants from earlier ages. Such places are where life first evolved.
Waimangu takes claim to the most botanically rich geothermal area in New Zealand. The first species we encountered was prostrate kānuka (Kunzea ericoides var. microflora) which is small, at under two metres. The extreme heat of the ground means this species has to grow roots horizontally across the cooler exposed ground, becoming naturally bonsaied by heat. En masse, the effect of horizontal feathery bands amongst white silica-rich earth achieves a rare minimality in New Zealand’s landscape. The second species is the strange Psilotum nudum a fern with a skeletal appearance punctuated by bright yellow sporangia. South of Northland and Coromandel, it appears in correlation with geothermal areas on cliff faces and fumaroles. Another two species of fern share a similar habitat around a small geyser and heated stream. Stunted forms of Cyclosorus interruptus grow here with smaller fronds and shorter rhizomes than those of cooler swamp habitats. A cascading of wall of weeping fronds from Neprolepis flexuosa backgrounds a small geyser fountain. This gracile, weeping appearance and lack of tubers differentiates it from the highly invasive ladder-fern. On the mainland, N. flexuosa is confined to North Island geothermal fields only. Further along the track, silica terraces are once again forming in the valley as a thick white crust. Moss carpets, silica gravels and kānuka lend a Japanese garden aesthetic to much of the walk. Upon reaching the shore of Rotomahana we come across Carex secta (Purei) amidst a drowned kānuka forest. This forest was submerged when the Tarawera eruption tore Rotomahana to twenty times its size and 170 metres deeper.
