Basalt

Two geologists · four walks · all year

The field stopped moving in 1974 and has not finished cooling

Eleven square kilometres of black rock that was a farm, a road and four houses. We walk on it every week and we can still find places where a hand held near a crack comes back warm.

The four walks
A river of orange lava seen from above at night.

What you are standing on

Two kinds of rock, and the difference decides everything about the walk. Pahoehoe is the smooth ropey stuff you can cross in trainers. A'a is the broken clinker that eats boots and ankles and is most of the eastern half.

There is no path. There are cairns, put in by us, and they move every spring because the surface does.

EruptionFebruary 1974, eleven weeks

Field11.2 km², up to 40 m deep

Hottest crack measured this year68°C at 1 m

Houses under itfour, one still visible

Plants on it so farlichen, and one birch

A dark lava flow cutting across black ground from the air.

Four walks

All four leave from the same gate and all four end there. Boots are not optional on any of them and we will turn you around at the gate if you turn up in trainers, which happens about once a fortnight.

Deep ravines cut into a dry rock plateau, from the air.

The edge, two hours

Along the margin where the flow stopped, with the old field wall on one side and forty metres of rock on the other. Flat, smooth, and the one walk a reasonably fit eight-year-old can do.

£24 · 2 hours · 3 km · daily at 10:00

A deep red-rock canyon under a pale sky.

Across, five hours

The whole width, pahoehoe to a'a and back again, two hundred metres of climb and about four hundred small ones. Six people maximum and a hard turnaround time at 14:00.

£62 · 5 hours · 9 km · Tue, Thu, Sat

Coarse grey gravel filling the frame.

The tube, three hours

Into a lava tube with head torches and helmets, both lent. Two hundred metres in, one crawl of about four metres, and total darkness for the ninety seconds everybody remembers.

£48 · 3 hours · helmets provided · Wed, Sun

Pale river channels braided across dark ground, from the air.

The house, ninety minutes

To the one roof still standing out of the rock, with the family's photographs of it from before. We do not go inside and we do not take anything. The walk is free for anybody from the valley.

£18 · 90 minutes · 2 km · Fridays at 17:00

Braided pale channels running across dark volcanic ground.

Who should not come

We would rather lose the booking than have this conversation at the gate, so it is on the page instead of in the small print.

Anyone in trainers
A'a is volcanic glass with the texture of broken crockery. It goes through a canvas sole in an afternoon and through the skin under it just as easily.
Bad ankles
Nothing on the crossing is level for more than two steps. If you roll ankles on ordinary ground, do the edge walk and enjoy it instead.
Wheelchairs and pushchairs
None of the four is possible, and we are genuinely sorry. The visitor centre at the bottom has the same rock under glass and the same two of us on a Thursday.
Under eights
On the edge walk and the house walk they are welcome and they usually love it. On the crossing and in the tube, no, at any age you would like to argue for.
Dogs
Paws and a'a are a bad combination and there is nowhere to put a dog down for five hours. The edge walk on a lead is fine.
Anybody in a hurry
We stop a lot, because the whole point is what is under the stopping. If you have a ferry at three, take the ninety minutes.

Walks are cancelled for wind over 20 m/s, for fog, and for the two days a year the gas monitor at the north vent goes over its limit. You get a text and your money back the same day.

Close-up of loose grey volcanic gravel.

Two of us

Both volcanologists, both here since the mapping project in 2009, both living in the village at the bottom of the field. Between us we have walked the crossing about nine hundred times and we still stop at the same crack.

Everything we know about the 1974 flow came from the people who watched it, and some of them still come on the Friday walk.

Where the gate is