Effusive Volcanism on Earth and Mars

Abstract

Effusive eruption products, specifically lava flow-fields, can provide an important window into the geologic history of planetary bodies. This dissertation investigates the geomorphological characteristics of volcanic terrains formed by effusive volcanism to infer eruption dynamics, and, in the planetary context, the magmatic and volcanic evolution of Mars. We investigate the 2014-2015 Holuhraun lava flow-field in the Icelandic highlands and the youngest volcanic terrain on Mars-Elysium Planitia-with a multi-faceted approach of surface and subsurface characterizations, based on remote sensing data, including orthomoasics, Digital Terrain Models (DTMs), and subsurface radar products. To better understand effusive eruption products and quantify their controls, we begin by examining the 2014-2015 Holuhraun eruption site using a combination of remote sensing data and ground-truth field observations from the summers of 2015-2019. This part of the dissertation includes three complementary investigations. First, a detailed characterization of the lava flow morphologies (i.e. lava facies) shows that the lava flow-field is dominated by transitional lava types including, rubbly pahoehoe, slabby pahoehoe, and spiny pahoehoe, instead of traditional pahoehoe and 'a'a lava types. Second, we investigated surface roughness of the entire lava flow-field to evaluate if root-mean-square (RMS) height deviation, Hurst exponents, and breakpoints can be used to distinguish between different lava facies in DTMs with pixel scales of 0.05 to 0.5 m/pixel. Our findings show that most lava facies are indistinguishable by surface roughness characteristics down to a 5 cm baseline and thus, despite this metric being commonly used, surface roughness is a poor discriminator to uniquely identify transitional lava types based on remote sensing data. Third, to address the scientific gap of understanding the controls on lava morphologies, the 2014-2015 Holuhraun eruption was then examined to test the hypothesis that lava morphologies are controlled by effusion rates. We used a combination of new constraints on emplacement chronology and two independently derived time-averaged discharge rate (TADR) data sets to link lava supply rates with the final emplacement products. Our findings show that, in the beginning of the eruption, the lava facies are dominantly controlled by the effusion rate at the vent and, as the eruption progressed, the transport system and thus local effusion rates become a stronger control. Finally, we present a novel perspective on Elysium Planitias' turbulent history on Mars. Using insights learned from the Holuhraun eruption, we mapped the lava flow-fields spread throughout Elysium Planitia to evaluate the flow areas, thicknesses, and volumes using orthoimages in combination with SHAllow RADar (SHARAD) sounder data. Our findings show that the eruptive history can be distinguished into five large events forming the major volcanic units: Grjótá Valles lavas, Rahway Valles lavas, Marte Vallis lavas, Cerberus Plains lavas, and Athabasca Valles lavas. The lava infilling Athabacas Valles is representing the lower end of erupted volumes with 7.27x10e3 km3 and lavas occupying Marte Vallis on the upper end with 16.33x10e3 km3. The subsurface evaluation of the study site also reveals a valley centered around 4.0 deg N and 165.5 deg E that is the upper extent of Marte Vallis. This channel is interpreted to be likely an aqueous carved valley that is now buried by Late Amazonian lavas. The pristine lava surfaces and the recent detection of seismic activity in Elysium Planitia may imply that Mars is still volcanically active in a geological context and could erupt again in the future.