If you know what you’re looking for, it’s easy to spot evidence of Aotearoa’s very explosive past.

Price: $63,390 ($6440 Clean Car penalty).

Powertrain: 2.8-litre turbo diesel four, 150kW/500Nm, part-time 4WD, six-speed auto, 9.5L/100km, 252g/km.

Vital statistics: 5325mm long, 2020mm wide, 1830mm high, 3090mm wheelbase, 265/60 R18 tyres.

We like: Improved open road ride; corners better; wider stance improves look; safety spec.

Not so much: Access is quite a climb; dated interior; spend.

THE Hinuera Gap is a wide valley, intersected by State Highway 29 that carries traffic from SH1 east of Cambridge, over the Kaimais and on to Tauranga.

A peaceful, bucolic setting these days. But do those cliffs seem unusual in appearance? Maybe you’ll think it is almost as if a giant river once ran through here.

Correct. Thousands of years ago the Hinuera Gap was the course of the river we now call the Waikato. It used to flow from an ancient lake called Huka which extended slightly north-east of our current Lake Taupo, down through the Hinuera Valley and Hauraki Basin, and into the Firth of Thames.

Twenty-seven thousand years ago there was a super eruption, called Oruanui. This totally changed everything. The massive blast threw an estimated 430 cubic kilometres of fall deposits into the air, which then returned to earth and deeply blanketed a 30,000 square kilometre area with volcanic debris. The eruption also completely filled Lake Huka and instead created a giant caldera. Lake Taupo.

The caldera slowly filled, the water level rising to an estimated 75 metres above its present height because all that volcanic debris had blocked off any outlet. Then, after about two decades the blockage breached. Eighty cubic kilometres of water surged down the ancient river.

This flood took with it massive amounts of debris, so much so that it blocked off the Hinuera Valley and Hauraki Basin and forced the river to abruptly spill westward into the Hamilton Basin and eventually to the Tasman Sea. That’s now the route of our Waikato River, leaving only a ‘remnant’ river, the Waitoa, flowing through the Hinuera Gap.

Wow. And the good news is that you can see all of this. If you know where to look. So the Maetzigs hit the road to tour through New Zealand’s volcanic past, checking out all those thousands of years-old clues to what was an extraordinarily violent time.

Our vehicle of choice was a Toyota Hilux SR5 Cruiser, the latest iteration of New Zealand’s second-most popular utility vehicle, with widetrack designation.In addition to the wheel set being pushed out, ride height is increased and there is a different suspension tune, in the interests of a more secure ride. To accommodate that wider track the wheel arches are upsized, which helps give this Cruiser a look of real substance. Nice.

We started from our home in Taranaki and headed north. Once on SH29 we soon spotted the unusual cliffs bordering either side of the Hinuera Gap. Actually, these cliffs go back much further than the Oruanui eruption of 27,000 years ago. Specifically, the cliffs are made of Ongatiti ignimbrite, the pumice and ash-laden pyroclastic flow from a massive volcanic eruption that occurred 1.3 million years ago and which catastrophically buried vast areas of the North Island up to 200 metres deep before being welded into rock by the extreme heat of the big blast.

Experts say that initial eruption resulted in the most widespread ignimbrite deposits on earth – it covered an estimated 45,000 sq km. Not only that, but there were at least 11 major subsequent eruptions, all of which also had pyroclastic flows. As a result, the ignimbrite is everywhere. Cathedral Cove on the Coromandel Peninsula is made of ignimbrite from that eruption and the subsequent blasts, and thousands of years of erosion have exposed it on cliffs and bluffs around the likes of Otorohanga and Te Kuiti. Geologists have also discovered the ignimbrite deeply buried in Auckland and Wellington. And you can spot the same thing most of the way down the 27,000 year-old ‘new’ course of the Waikato River.

These days the cliffs either side of the Hineura Gap are well-known for two things – quarrying, which has been going on for at least 130 years, and rock climbing. We headed to the last remaining such quarry, operated by a company called Hinuera Natural Stone which cuts out the ignimbrite and crafts it into blocks for use as building material such as cladding.

After gaining permission and donning the appropriate safety gear, we put the Hilux into 4WD High and headed off down a very rough and muddy track to get some photographs. The ute easily did the job. This vehicle has a 140mm wider track than as standard 4WD Hilux, and there is a 20mm increase in ride height, so it was doddle for the ute to get through the mud, its 150kW/500Nm turbodiesel not in the slightest bit worried about any of the steeper slopes encountered.

As we departed the quarry, we noted something very interesting – the Hinuera Gap is a very short distance from the Waikato River. Maybe just a couple of kilometres away from the location where the river abruptly turns left and heads down what is now Lake Karapiro towards Cambridge. We tried to imagine what it must have been like during that cataclysmic period in New Zealand’s geological history when that 80 cubic kilometres of water and debris suddenly let go out of the lake and crashed its way downriver.

These days the Waikato journeys down lush countryside as it makes its way to the sea at Port Waikato. But if you drive the route of what is now New Zealand’s longest river, it’s easy to recognise remnants of that catastrophic period in New Zealand geological history. Towering cliffs slowly eroding away, exposing the rock-hard pyroclastic material left behind. And in the upper reaches of the Waikato, plenty of geothermal activity as if the scenery is still simmering. Remarkable.

It could be said that this assignment involved a fossil-fuelled vehicle touring through fossilised country. That’s true – and the Hilux gets punished for that.

The SR5 Cruiser is the most expensive model in the Hilux range. The 2.8-litre turbo-diesel ute also cops the biggest Clean Car Programme fee. An electric vehicle for the same money would be eligible for a $7015 rebate; that’s a $13,455 feebate difference.

Diesel utes pay a road user charge of $76 per 1000km, EVs are exempt. During our sortie through the volcanic plateau we felt it rather ironic that we had to take on some rapidly deteriorating road surfaces. Surely the result of not enough money being spent on their maintenance? It seemed to me this ute was better able to handle the thump and bump of potholes and bad road surfaces than the average EV.

The central North Island, particularly up in the volcanic plateau where forestry and farming is prevalent, is ute country. It would be nice if they were cut more of a break.