Contents

20 April 1990
Vol 248, Issue 4953

About The Cover

The Champagne Pool, named for its CO2 bubbles, provides an interesting window into fluid processes beneath Waiotapu, the largest area of surface thermal activity in New Zealand. The pool occupies a 900-year-old hydrothermal explosion crater. Evaporation cools the surface waters from 100°C to about 75°C, producing the steam. Amorphous silica, blown by the wind to the sides, settles as an orange coating that contains 80 parts per million of gold and 175 parts per million of silver. See page 323. [Photograph by L. M. Cathles]