Steam of the Fire Goddess

Near the Bay of Plenty on New Zealand's North Island is an uneasy, earth-quaky land full of hot springs, geysers, active volcanoes and puddles of boiling mud. Trying to tap the power of this natural boiler, government engineers have dotted the area with wells, out of which steam pours with a screeching roar that makes jet engines sound like whippoorwills. Last week six of the screaming jets had been harnessed to a turbine and were generating 6,400 kw. of geothermal electricity.

According to native Maori legend, an ancient chief named Ngatoro-i-rangi got caught in a mountain blizzard near Waira-kei and had the presence of mind to call for divine help. Down from the Maoris' ancestral (and warmer) homeland, Ha-waiki, came the fire goddess. Wherever she stepped, a volcano bloomed. She warmed Ngatoro-i-rangi so bounteously that the whole region where the blizzard was blowing is still boiling over.

Modern New Zealand geologists have another explanation. In some past age a strip of land 120 miles long and up to 30 miles wide sank below the surrounding land and got cracked up in the process. The trench was later filled partially with silt and volcanic debris, but the cracks did not heal. They still lead down toward molten rock perhaps 30,000 ft. below the surface.

The whole trench is conveniently capped by a layer of impermeable siltstone a few hundred feet below the present surface. Beneath it, porous rock accumulates steam like a kind of natural boiler. A well only 1,000 ft. deep taps this reservoir. Some of the steam is "juvenile," coming from water that was trapped in the deep interior when the earth was young and rising upward through the deep faults. The rest derives from surface water that has trickled down through cracks and been turned to steam by heat from below. When the steam gets to the surface, its pressure is about 190 Ibs. per sq. in. and its temperature about 470DEGF.

New Zealand's engineers made a close study of the world's only other big geothermal power plant, at Larderello in central Italy. Larderello's steam has been used since 1913 to drive power plants. New Zealand's steam needs less treatment to free it of foreign matter and seems to be far more plentiful. Though authorities at first hesitated to schedule expensive powerhouses in the geothermal region for fear that the steam wells might peter out, nothing of the sort has happened; after eight years the oldest of the steam wells is screaming as loud as ever.

The new turbine is only a beginning. Eventually New Zealand plans to get 250,000 kw. of geothermal electricity out of the Wairakei region, and hundreds of square miles of steam land are awaiting exploitation in the neighborhood.

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