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- Genre: Masters Thesis
Description
Ascraeus Mons (AM) is the northeastern most large shield volcano residing in the Tharsis province on Mars. AM has a diameter of ~350 km and reaches a height of 16 km above Mars datum, making AM the third largest volcano on Mars. Previous mapping of a limited area of these volcanoes using HRSC images (13-25 m/pixel) revealed a diverse distribution of volcanic landforms within the calderas, along the flanks, rift aprons, and surrounding plains. The general scientific objective for which mapping was based was to show the different lava flow morphologies across AM to better understand the evolution and geologic history.
A 1: 1,000,000 scale geologic map of Ascraeus Mons was produced using ArcGIS and will be submitted to the USGS for review and publication. Mapping revealed 26 units total, broken into three separate categories: Flank units, Apron and Scarp units, and Plains units. Units were defined by geomorphological characteristics such as: surface texture, albedo, size, location, and source. Defining units in this manner allowed for contact relationships to be observed, creating a relative age date for each unit to understand the evolution and history of this large shield volcano.
Ascraeus Mons began with effusive, less viscous style of eruptions and transitioned to less effusive, more viscous eruptions building up the main shield. This was followed by eruptions onto the plains from the two main rift aprons on AM. Apron eruptions continued, while flank eruptions ceased, surrounding and embaying the flanks of AM. Eruptions from the rifts wane and build up the large aprons and low shield fields. Glaciers modified the base of the west flank and deposited the Aureole material. Followed by localized recent eruptions on the flanks, in the calderas, and small vent fields. Currently AM is modified by aeolian and tectonic processes. While the overall story of Ascraeus Mons does not change significantly, higher resolution imagery allowed for a better understanding of magma evolution and lava characteristics across the main shield. This study helps identify martian magma production rates and how not only Ascraeus Mons evolved, but also the Tharsis province and other volcanic regions of Mars.
A 1: 1,000,000 scale geologic map of Ascraeus Mons was produced using ArcGIS and will be submitted to the USGS for review and publication. Mapping revealed 26 units total, broken into three separate categories: Flank units, Apron and Scarp units, and Plains units. Units were defined by geomorphological characteristics such as: surface texture, albedo, size, location, and source. Defining units in this manner allowed for contact relationships to be observed, creating a relative age date for each unit to understand the evolution and history of this large shield volcano.
Ascraeus Mons began with effusive, less viscous style of eruptions and transitioned to less effusive, more viscous eruptions building up the main shield. This was followed by eruptions onto the plains from the two main rift aprons on AM. Apron eruptions continued, while flank eruptions ceased, surrounding and embaying the flanks of AM. Eruptions from the rifts wane and build up the large aprons and low shield fields. Glaciers modified the base of the west flank and deposited the Aureole material. Followed by localized recent eruptions on the flanks, in the calderas, and small vent fields. Currently AM is modified by aeolian and tectonic processes. While the overall story of Ascraeus Mons does not change significantly, higher resolution imagery allowed for a better understanding of magma evolution and lava characteristics across the main shield. This study helps identify martian magma production rates and how not only Ascraeus Mons evolved, but also the Tharsis province and other volcanic regions of Mars.
ContributorsMohr, Kyle James (Author) / Williams, David A. (Thesis advisor) / Christensen, Phil R (Thesis advisor) / Clarke, Amanda (Committee member) / Arizona State University (Publisher)
Created2017
Description
Among the deadliest of explosive volcanic hazards are pyroclastic surges – fast-moving, hot, dilute ground-hugging currents that overtop topography and leave complex deposits. Understanding the link between surge dynamics and their deposits is crucial for forecasting the impacts of future eruptions. To investigate surges, two sets of scaled laboratory experiments were conducted. Set 1 released fluid pulses into less-dense ambient water (3-m flume). Pulse fluids were saline solutions with and without particles, and alcohol-water-particle mixtures. Non-dimensional numbers are calculated using both input parameters and measured outcomes. Inputs - fluid density, particle size and concentration, and volume of fluid released - were varied to explore a range of conditions. Key output parameters obtained by video analysis are flow thickness and propagation velocity. Propagation velocity, Re, and Ri increased with increasing pulse density, while Pn decreased. Lab Re values indicate fully turbulent flows, consistent with natural flows. Lab Ri closely matched nature and flow propagation was largely controlled by negative buoyancy, with entrainment playing a minor role. All flows began as subcritical (Fr<1). Alcohol-water-particle runs exhibited buoyancy reversals caused by particle sedimentation, characterized by gradual deceleration and late-stage formation of buoyant plumes. Saline runs maintained nearly constant velocities. In the second set of experiments, alcohol-water-particle mixtures were pulsed over particle bed. Various substrate topographies were tested (flat, mound-trough sequences, steps, wedges). Deposits thickened in troughs and thinned on peaks. Progressive climbing dunes formed on the lee side of the second peak of double peaks and peak-trough combinations, and in step-up topographies. Regressive climbing dunes formed on the stoss side of the first peak of peak-trough combinations and step-down topographies, and on the stoss side of mounds. Climb angles were 16 to 36°, consistent with those documented in pyroclastic surge deposits. The occurrence of both regressive and progressive climbing dunes suggests localized transitions between subcritical and supercritical flow. No cross-beds formed on flat substrates, suggesting that complex substrate topography is required for bedforms to occur in nature. A code benchmarking effort is underway in which targeted model runs will be compared to both sets of experiments in order to develop comprehensive hazards prediction tool.
ContributorsRagavan, Rupa (Author) / Clarke, Amanda (Thesis advisor) / Semken, Steven (Committee member) / Roggensack, Kurt (Committee member) / de'Michieli Vitturi, Mattia (Committee member) / Arizona State University (Publisher)
Created2023