Dating Castle Geyser: Preliminary Results and Broad Speculations on the Geologic Development of Geysers and Hydrothermal Systems in Yellowstone National Park, Wyoming, USA

Abstract

How old are Yellowstone’s geysers? How do geysers grow? What do the growth of geysers and the geologic development of hydrothermal systems tell us about deeper geologic and magmatic processes in the Yellowstone supervolcano? Seven carbon 14 (14C) dates have been successfully obtained from geyser and hot spring deposits at Castle Geyser, in the Upper Geyser Basin in Yellowstone. Castle Geyser has an imposing cone that sits upon a broad terrace or shield of sinter. The shield upon which the geyser is built dates from 8,800 to 10,400 years ago, while all dates from the cone of Castle are younger than 1,040 years. 3-D laser mapping is a new technique that holds great promise in small-scale geologic investigations. A preliminary 3-D laser map of Castle Geyser allows clear identification of at least three distinct stages in the growth of the geyser. The gap of dates between approximately 10,000 years from the shield and 1,000 years from the cone, combined with distinct morphologies illustrated by 3-D laser mapping, suggests that Castle Geyser has had pulses of activity followed by times with much less activity. Many geologic systems, from volcanoes to geysers, operate in a similar pulse (eruptions) and pause (between eruptions) style. Perhaps we are living in a millennial (or longer?) pulse of activity and we are fortunate to be able to see so many geysers in Yellowstone.