Four places in the North Island to see post-eruption gorges
If you spend much time tramping around the central North Island, sooner or later you’ll notice the extraordinary nature of its ignimbrite gorges. Gorges of a warm brown colour, fluted, columned, with very fine-grained rock. Ignimbrite is volcanic in origin, and much of the central North Island, including the banks of the upper Waikato River, is made from the stuff.
Despite admiring ignimbrite, I’d never fully understood what it is until reading Geoff Chapple’s book Terrain. Now I know the term derives from ignis (fire) and imbris (storm), and was coined by New Zealand geologist Patrick Marshall in the 1930s. The name reflects its origins from rare but highly explosive rhyolitic eruptions.
Ignimbrite results from magma with a high silica content – more than 70 per cent – which makes it much less pliable than basalt or andesite. Chapple says: “It holds its gases close, it bulges only slowly, it’s the Methuselah of all magma, but when it does erupt, it does so with the force of an asteroid strike.’
These four ignimbrite gorges are all exquisite in their own way, and make excellent destinations for trampers.
Te Whaiti Nui A Toi Canyon, Whirinaki Forest Park
This is a particularly fine example of an ignimbrite gorge, and a very accessible one, lying only 20min walk along Whirinaki Track. A footbridge spans the gorge, but photographers will want to scramble down to the river to get the best view.
Tauranga Taupo River, Kaimanawa Forest Park
Cascade Hut is one of only a handful of huts in Kaimanawa Forest Park, and is superbly located to see this spectacular gorge in the upper Tauranga Taupo River. Easiest access is from Clements Mill Road, where the 4-5hr Hinemaiaia Track climbs over a forested ridge to reach the river. Cascade Hut is sited near the river’s confluence with Cascade Stream, and the gorge is a short scramble upstream.
Tree Trunk Gorge, Kaimanawa Forest Park
One of the most fearsome ignimbrite gorges is this narrow slot canyon in the Tongariro River, on the edge of Kaimanawa Forest Park. Tree Trunk Gorge Road comes off SH1, south of Turangi. A road bridge spans the gorge, where onlookers can gain a giddy glimpse of the defile far below. An informal track leads up the true left to the opening of the gorge. Water-slick columns of ignimbrite arch around what seems like the mouth of Hades, with spray rising up and the ominous thundering of downstream whitewater. Kayakers often test their mettle against this gorge but as the names of the rapids suggest – Mother-in-law’s Nightmare, Oppat’s Ordeal, General Disaster and Kirkham’s Mistake – it’s a serious run that has claimed a few lives.
Waihaha River, Pureora Forest Park
The Waihaha River drains a substantial portion of the eastern Hauhungaroa Range in Pureora Forest Park. Beginning from a car park off the Western Bays Road, SH32, this pleasant and easy track leads up the true left of the river to Waihaha Hut, with views of the gorge en route.