Research finds drought alters Mammoth Mountain's carbon dioxide emissions

Thirty years ago, on the flanks of a volcano in California's Sierra Nevada range, trees began to die en masse, suffocated at their roots by carbon dioxide from the mountain's depths after a swarm of small earthquakes.

Scientists began to monitor the volcano's emissions more closely after a wave of tree deaths on the mountain.

The amount of snow and ice in the Sierra Nevada is linked to the ebb and flow of carbon dioxide emissions from the mountain.

Hilley is a professor of geological sciences in the School of Earth, Energy and Environmental Sciences.

With less than a week remaining in the state's wet season and no major snowstorms in the forecast, the research published March 9 in Geophysical Research Letters comes at a bad time.

By the end of this century, state officials predict the Sierra Nevada snowpack will decline by 48 to 65 percent from the historical April 1 average.

The lake is named Horseshoe Lake.

Hilley and his colleagues analyzed the carbon dioxide emissions from Horseshoe Lake for six years. The southwest rim of Long Valley Caldera was formed by a supervolcano eruption 760,000 years ago.

During the spring of 2017, the amount of carbon dioxide in the air was 20 percent less than it was in the fall. The downshift coincides with the emergence from the intense dry spell and the biggest Sierra Nevada snowpack in decades.

Carbon dioxide emissions in the Horseshoe Lake tree-kill area changed over time for reasons unrelated to a brewing eruption, according to research by a volcanologist from the US Geological Survey.

Lewicki and Hilley sought an explanation for the variations and developed mathematical models to test out plausible mechanisms. Carbon dioxide can be washed away by snow and rain. Their calculations show that the low springtime CO 2 levels observed in the year are not due to precipitation.

The most likely explanation for the seasonal changes in the carbon dioxide emissions is an underground crack, which can be seen in the vegetation patterns and landscape. Changes in the distribution of stress across the mountain range seem to open and close the fault like a valve, or like tiny gaps between old floorboards that flex under shifting weight.

The authors found that the force on the fault peaked in the winter as the snow accumulated across the Sierra Nevada. When the weight of snow and water in the mountains flexed Earth's crust, the carbon dioxide emission levels went down.

The study doesn't provide a physics-based model of the fault's movement and how gas flows through it.

Predicting eruptions in the future.

The ability to distinguish between CO 2 fluctuations driven by climate and those driven by an impending eruption will enable better hazard forecasts, which are based partly on signs that rising magma is triggering earthquakes.

Scientists can view the data in close to real time, thanks to the continuous monitoring of the ground around some of the United States active volcanoes. In the past, scientists had to go into a volcanic area in advance of an eruption, or even between eruptions, to collect the gas for later analysis. Hilley said it was real Indiana Jones-type stuff.

The difficulty of collecting volcanic gases has resulted in limited records, sometimes with only a single snapshot of a volcano's degassing in any given year, which makes it difficult to detect changes that may warn of an eruption.

As scientists gain access to more volcanic emission data, the new study offers a glimpse of insights, thanks in part to the development of less expensive and more durable instruments.

Hilley said that they hope to have a record of what the gas is doing in the next couple years.

More information: George E. Hilley et al, Seasonal and Multiyear Changes in CO 2 Degassing at Mammoth Mountain Explained by Solid‐Earth‐Driven Fault Valving, Geophysical Research Letters (2022). DOI: 10.1029/2021GL096595 Journal information: Geophysical Research Letters Citation: Research finds drought alters Mammoth Mountain's carbon dioxide emissions (2022, March 30) retrieved 30 March 2022 from https://phys.org/news/2022-03-drought-mammoth-mountain-carbon-dioxide.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.