Volcanic Hazards in Death Valley's Ubehebe Crater: Cause For Concern?
Researchers from Columbia and Purdue universities have recently utilized an interesting method to infer the timeframe of the volcanic events which created Ubehebe Crater in Death Valley National Park. By examining rock samples which had been created in those events, these researchers are the first team to utilize Beryllium-10 dating techniques to infer time periods of explosive volcanism. Their study, published in Geophysical Research Letters this month, could give important insight into what type of volcanic danger, if any, exists in the southeastern California desert.
Since measurements began in 1923, it has been largely accepted that a massive caldera exists underneath Yellowstone National Park. A reminder of the area’s volcanic origins, this caldera has been of great interest to geologists and volcanologists, as well as a great concern with regard to the safety of not only park visitors, but to nearby population centers as well. In California’s Death Valley National Park, a different form of potential volcanic activity exists which could also pose a potential hazard to park enthusiasts. Though not on the same scale as the danger posed by Yellowstone, the hazards associated with the phreatomagmatic activities which created Ubehebe Crater are certainly worth consideration, as nearly one million visitors enter the area in a given year.
Typically, a phreatomagmatic eruption occurs when underground water comes into contact with magma; this interaction causes a great deal of steam release, and can result in explosive activity under certain conditions. Thus, it makes sense that these types of eruptions would be more prevalent in environments where water is plentiful. Given that the landscape surrounding Ubehebe is renowned for its aridity, knowledge of when the volcanic activity which shaped the crater actually occurred could give important insight into how much water was actually present at the time, as well as whether or not there is any potential for such activity in the foreseeable future.
To take these measurements, the research team used Berillium-10 surface exposure dating of rocks which had been ejected from previous eruptions. This element is normally found on Earth to exist in its most stable, Be-9 isotope; the Be-10 isotope is formed in the atmosphere through the interactions of cosmic rays and particulate matter, and accumulates at low levels in soil surfaces around the globe. These levels stick around for a very long time (a half life of over 1.25 million years), and a measurement of these concentrations can be used to infer the time frame of previous volcanic activity. Though previous evidence has suggested that at least 50 eruptions may have occurred over time in the area surrounding Ubehebe, the specific timing of these events is a matter of much debate.
Specifically, the authors of the study sought to address several questions. These included whether the area’s volcanic events corresponded to a period where precipitation was much greater, such as near the end of the last ice age, as well as whether the eruptions were independent of weather-related water (and instead related to residual sedimentary groundwater). Of the material which was examined, a great deal corresponded to a period from between 800 and 2100 years ago, suggesting that the formation of the crater was actually fairly recent. Based on precipitation studies which had previously been conducted throughout the areas, the researchers concluded that the explosive events which created Ubehebe appear to have occurred during a period where the region was still remarkably dry; this indicates that the phreatomagmatic activity which created the crater did not require an increase in rainfall to have occurred.
Instead, the authors of the study believe that permanent groundwater may exist in more recent sedimentary deposits, and that previous volcanic activity resulted when magma travelled upward into these deposits. Further, they argue that even very small magma chambers may be adequate to unleash these explosive events, and that these pockets of molten material are definitely believed to exist.
“Additional small [magma] bodies may exist in the region, even if they are sufficiently small not to show up geophysically,” said Nicholas Christie-Brink, one of the researchers. “There is no basis for thinking that Ubehebe is done.”
With this information in mind, the potential for volcanic events similar to those which created Ubehebe certainly seems to be significant, despite the dry climate in Death Valley National Park. Further volcanic research, including the dating of basaltic flows underneath the crater, will ultimately be necessary to learn more about these dangers, but this study provides an important starting point for determining how much danger may actually exist for national park visitors.
Despite the potential hazard, there is probably no reason for undue concern just yet. Stephanie Kyriazis, a park education specialist, suggests that “right now, we’re not planning to issue an orange alert or anything like that.”