Geology and ground-water resources of the Los Alamos area, New Mexico

Griggs, Roy L.; Hem, John David

doi:10.3133/wsp1753

Cited by 12 publications

(2 citation statements)

References 5 publications

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“…The Pajarito Plateau in north-central New Mexico is formed primarily of volcanic ash that was lithified into a solid rock called tuff (Griggs and Hem, 1964;Smith et al, 1970) (Thompson et al, 1993). Approximately 12,000 years ago, the Holocene brought warming temperatures, accompanied by melting glaciers, disappearing pluvial lakes, and precipitation that transitioned from snow dominated to rainfall dominated.…”

Section: Cycles Of Erosion and Depositionmentioning

confidence: 99%

Climate Change in New Mexico Over the Next 50 Years: Impacts on Water Resources

Dunbar¹,

Gutzler²,

Pearthree³

et al. 2022

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All water that we use in New Mexico originates as rain or snow falling onto the landscape, which either goes to groundwater or surface water or returns to the atmosphere. Of the precipitation that falls on the state, 1.6% runs off into streams and rivers, and 1.8% infiltrates into the ground, recharging subsurface aquifers. Much larger proportions are transpired by plants (78.9%) or evaporated (17.7%). The impact of climate change on all of these pathways will affect our state's water budget. Notably, because of the larger percentages of water lost to evaporation or transpiration, even very small changes in these factors will result in large changes to runoff and recharge. As mentioned in Chapter 2, the climate will continue to warm over the next 50 years, likely without an increase in precipitation, leading to greater statewide aridity. Hydrological modeling indicates declines in both runoff and recharge going forward, amounting to 3% to 5% per decade for both quantities. Historical trends in runoff indicate significant year-to-year variability, as do trends in soil moisture and recharge. But all are generally decreasing, consistent with the results of climate models that project a drying climate. Combining the historical trends with modeling of future changes, significant decreases in runoff and recharge seem very likely. TERRESTRIAL ECOSYSTEMSClimate is a fundamental driver of ongoing and future vegetation changes in New Mexico. Future changes in vegetation will affect the distribution and abundance of water resources in New Mexico. Major shifts in climate and vegetation across New Mexico's landscapes have occurred in the past, but the scale and rate of recent and projected climate change is probably unprecedented during the past 11,000 years. Recent warming, along with frequent and persistent droughts, have amplified the severity of vegetation disturbance processes like fire, physiological drought stress, and insect outbreaks, driving substantial changes in New Mexico vegetation since the year 2000. Ongoing and projected vegetation changes include growth declines, reduced canopy and ground cover, massive tree mortality episodes, and species changes in dominant vegetation-foreshadowing more severe changes to come if current warming trends continue as projected. Such major alterations of New Mexico vegetation likely will also have substantial ecohydrological feedbacks with New Mexico water resources. Since water-related environmental stresses occur in parallel with water supply shortages for people, such climate-change-driven water stress could lead to increasing conflict between managing declining water available for human use (e.g., irrigation) and retaining "wild" water for the maintenance of historical ecosystems.

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Section: Cycles Of Erosion and Depositionmentioning

confidence: 99%

Climate Change in New Mexico Over the Next 50 Years: Impacts on Water Resources

Dunbar¹,

Gutzler²,

Pearthree³

et al. 2022

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“…The VTM was first described by Griggs (1964) and mapped by Smith et al (1970) and has since been the focus of several volcanological, geochemical and geochronological studies (Heiken et al 1986;Stix et al 1988;Stix 1989;Stix and Gorton 1993, 1990a, 1990bBroxton et al 1995;Stix and Layne 1996;Spell et al 1996aSpell et al , 1996bJacobs and Kelley 2007;Slate et al 2007;Campbell et al 2009). The rhyolitic tephras are exposed in several sections, which were described by Stix (1989).…”

Section: Valle Toledo Member Rhyolitesmentioning

confidence: 99%

H2O and CO2 evolution in the Bandelier Tuff sequence reveals multiple and discrete magma replenishments

Waelkens

Stix

Eves

et al. 2021

Contrib Mineral Petrol

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The sequence of eruptions in the Bandelier magmatic system provides an opportunity to study volatile evolution through different stages of a large silicic magma chamber. The Lower Bandelier Tuff (LBT) and Upper Bandelier Tuff (UBT) eruptions offer a snapshot of a pre-eruptive magma chamber primed for eruption, while the sequence of Valle Toledo Member (VTM) eruptions open a window into the temporal evolution of the chamber's upper regions between the two super-eruptions. We measured H 2 O and CO 2 concentrations in melt inclusions from the entire sequence of eruptions and identified three peaks in CO 2 concentrations: (1) in the middle of the LBT plinian airfall (increase in mean CO 2 concentrations from 27 ± 5 ppm at the base of the plinian to 173 ± 5 ppm in the mid-plinian); (2) in VTM group III (mean of 197 ± 5 ppm); and (3) in the middle of the UBT plinian airfall (mean of 54 ± 5 ppm at the base of the plinian to 101 ± 5 ppm in the mid-plinian). We propose that these increased CO 2 concentrations are due to injections of fresh magma into the system, whereby CO 2 -rich vapours exsolved from the injected magma percolated through the magma chamber to increase CO 2 levels. Although the sharp increase in the LBT plinian indicates a rapid succession of recharge events in a short period of time, the gradually increasing CO 2 levels through the final VTM phase and the UBT plinian indicate that recharge events may have been spread over a longer period of time before the UBT eruption. Based on the theoretical and observed gradients in H 2 O and CO 2 through the LBT and UBT sequence, we calculate a vapour phase equivalent to maximum 6.7 wt% of the magma body was exsolved from the LBT magma chamber; for the less degassed UBT, the exsolved vapour phase was maximum 4.2 wt% of the magma body. Our results indicate that the volatile composition of magmatic systems, with a particular focus on CO 2 , can record evidence of magmatic recharge into the system and be an important tool in deciphering recharge events.

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