YELLOWSTONE NATIONAL PARK — In this week’s Caldera Chronicles, the scientists of Yellowstone Volcano Observatory (YVO) discuss the origins, mapping and dating of small rock layers in Yellowstone National Park (YNP) that might be easily overlooked.
The weekly column is written by the scientists and collaborators of YVO. This week’s edition, written by Montana State University (MSU) graduate students Liv Wheeler and Stacy Henderson, takes readers through a quick geological history of YNP. According to the column, YNP’s geology is one of the most intensely studied in North America.
An early indigenous map of the area, described in 1805, was drawn on a bison pelt and indicated a volcano in the Yellowstone River. Geological mapping began in the 1870s during geographical surveys led by geologist Ferdinand Vandeveer Hayden. Later maps have improved and evolved, but the geology in YNP’s hard-to-reach landscape still needs some exposure.
“Although these maps — especially those that show the geology — have created a solid foundation for tourists and researchers alike, many remote or poorly exposed areas of Yellowstone have been generalized at broad scales, now requiring geologists to revisit these regions,” Wheeler and Henderson wrote.
Scientists have been mapping volcanic rock in YNP to understand the park’s history and to determine when eruptions occurred. The current maps have identified three major explosive eruptions, separated by periods of lava flows. Recently, a rock that was previously mapped at a certain age was dated by MSU geologists using new techniques, and the age no longer matched anything in the geologic record.
The rock, known as vitrophyre, was found in an area thought to be full of slow, thick lava flows. However, when tested with new dating techniques, the material suggested it came from an eruption — a smaller explosive eruption that did not form a caldera, but was still geologically significant.
“As scientists continue to write the story of Yellowstone’s eruptive history, remapping and dating are crucial for finding more of these overlooked units,” the column states. “If one previously unrecognized volcanic unit can be uncovered, how many more remain hidden in Yellowstone’s geologic record?”
