HOW DOES YOUR GEYSER GROW? 3-D LASER SCANNING AND PRELIMINARY 14C DATING OF CASTLE GEYSER, UPPER GEYSER BASIN, YELLOWSTONE NATIONAL PARK, WYOMING

Early explorers of Yellowstone described Castle Geyser as “a castellated turret” with “. . . its summit . . .formed . . . between large nodules of rock of the tint of ashes of roses . . .lined with a frost work of saffron.” (Doane, 1870; in, Bonney and Bonney, 1970). Geysers remain objects of inspiration and awe, and sources of geological fascination. In recent decades geyser studies have emphasized fluid chemistry and eruption dynamics and characteristics. New mapping and analytical techniques provide opportunities for reexamination of the geologic development of these features. It is known that geysers may have long periods of quiescence (e.g Steamboat from 1911 to 1961), and that geysers can blow themselves out and become hot springs (e.g. Excelsior Geyser, 1890). Some hot springs, such as Excelsior, can reinvigorate as geysers (1985). But what are typical “life stories” of geysers? How long to they last as geysers? How long do hot spring phases last? Marler (1956) documented a period of non-geyser activity in the development of Old Faithful that was long enough for a forest to grow on the site of the current cone. He reports a date of a tree killed by renewal of thermal activity at Old Faithful as 730 +/- 200 years. The development of 3-D laser scanning technology is opening new techniques for the visualization and interpretation of geologic features. Preliminary mapping of Castle Geyser demonstrates that the geyser may have developed through as many as four or five distinct stages. Provisional interpretation of geyser edifice morphologies suggests that periods of hot spring activity preceded pool-type geyser activity, which was followed by the development of the present cone geyser. In this study of Castle Geyser, sinter from a pool near the upper portion of the geyser cone was analyzed by 14C AMS techniques. The sinter dated 928 +/- 40 BP. This date, if confirmed, suggests that the development of this imposing geyser edifice may be much younger than the 5000 to 15000 years commonly assumed (Bryan, 2001).