| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | June 26, 2014 |
| Latest Amendment Date: | February 21, 2017 |
| Award Number: | 1420455 |
| Award Instrument: | Continuing Grant |
| Program Manager: |
Jennifer Wade
jwade@nsf.gov (703)292-4739 EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | July 1, 2014 |
| End Date: | December 31, 2018 (Estimated) |
| Total Intended Award Amount: | $275,231.00 |
| Total Awarded Amount to Date: | $294,231.00 |
| Funds Obligated to Date: |
FY 2015 = $88,424.00 FY 2016 = $94,576.00 FY 2017 = $19,000.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
520 LEE ENTRANCE STE 211 AMHERST NY US 14228-2577 (716)645-2634 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
411 Cooke Hall Buffalo NY US 14260-7022 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Petrology and Geochemistry |
| Primary Program Source: |
01001516DB NSF RESEARCH & RELATED ACTIVIT 01001617DB NSF RESEARCH & RELATED ACTIVIT 01001718DB NSF RESEARCH & RELATED ACTIVIT |
| Program Reference Code(s): | |
| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
Maars are volcanic craters cut into a pre-eruptive landscape, surrounded by low-profile ejecta or tephra rings. They are among the most abundant volcanoes on Earth, and occur most commonly in volcanic fields where there may be tens or hundreds of individual volcanoes. Maar eruptions present a significant hazard where populated regions overlap with volcanic fields. Because they involve violent explosions caused by mixing of hot magma and groundwater, their eruptions can produce a full gamut of dangerous phenomena including blast waves, pyroclastic flows, widely dispersed ballistic blocks, ash fall and far-travelled fine ash plumes, large-scale subsidence, and volcanic mudflows. Maars and their underlying plumbing structures - diatremes - can also be of economic importance, especially when the erupted magma is diamond-bearing kimberlite. Diatremes commonly resist erosion, and in exhumed landscapes such as the Colorado Plateau they form striking buttes and pinnacles (e.g., Shiprock, New Mexico, and parts of Monument Valley, Arizona). Despite their hazards and economic importance, many questions remain about the subsurface processes beneath maar-diatremes and the relationships of those processes to eruptive phenomena.
This project combines field studies at young maar-diatremes with innovative experiments that are intended to mimic, at the scale of meters, the processes that form the volcanoes. Field studies will focus on two young maars, Dotsero (Colorado, age ~4150 yrs) and Nilahue (southern Chile, erupted 1955) where original post-eruptive geometry can be well constrained, the tephra deposits are largely non-indurated and therefore amenable to component and clast shape/texture analysis, and sub-volcanic stratigraphy is well constrained, allowing us to link lithic clasts to their depths of origin. These results will be compared with and interpreted in light of experimental work that will use different configurations of buried explosives in artificial layered "geologies," allowing for characterization of crater geometry and detailed analysis of the composition of ejecta in terms of proportions derived from different depths. Explosions will be monitored with high-speed video, seismometers, and acoustic sensors in order to constrain dynamics, and post-experimental excavation will reveal the "diatremes" that are produced in order to explore the relationship between their structure and ejecta. Together, the field and experimental studies will greatly advance our understanding of maar-diatreme eruptions and the factors that control their hazards and potential economic resources.
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PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Maar-diatreme volcanoes are a type of volcano that is small but extremely violent. The violence results from explosions caused by the interaction of rising magma (molten rock) with groundwater. Rather than producing the typical cone shape that most people associate with volcanoes, maar-diatremes are actually craters in the landscape ("negative volcanoes" or maars). The subsurface explosions result in a funnel-shaped body of broken up rock and solidified magma that may extend a mile or more underground beneath a crater - this is called the "diatreme" and is actually where most of the volcanic work is done.
The work completed on this project is changing our understanding of phreatomagmatic maar-diatreme eruptions and resulting deposits. In previous models, explosions were often inferred to take place only at the base of a diatreme, with progressive downward migration as groundwater was used up. However, diatremes themselves contain much water that is heterogeneously distributed, and field evidence supports the existence of explosion sites at many vertical and lateral locations within them. Crater sizes have been used to estimate explosion energies, but this only works for single-explosion craters where the depth of explosion is independently known, and has limited value for multi-explosion maar-diatremes. Rocks that originated at depth (deep-seated) are found in ejecta ring deposits and have been taken to indicate the depth of the explosion that produced that bed. However, only relatively shallow explosions actually vent to the surface, and deep-seated rocks are gradually brought to shallow depths through step-wise mixing of multiple subsurface explosions. Grain-size of ejecta deposits is often inferred to indicate fragmentation efficiency or explosion violence. However, other factors strongly influence deposit grain size, including the depth-energy combination of an explosion and the interaction of an erupting jet with topography around a vent (e.g., crater), along with effects of mechanical properties of host rocks and recycling within the vent/diatreme.
These insights provide a foundation for future research into this important volcano type. In addition, the new understanding will be important in predicting the hazards associated with maar-diatreme volcanoes.
Last Modified: 03/01/2019
Modified by: Greg Valentine
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