Lava-Rise Plateaus and Inflation Pits in the McCartys Lava Flow Field, New Mexico: An Analog for Pahoehoe-Like Lava Flows on Planetary Surfaces

Abstract

Basaltic lava flows are common on the surface of the Earth and other terrestrial bodies. However, inflation-including a combination of initially rapid molten core thickening and gradual crustal growth-must be accounted for to enable accurate reconstructions of eruption parameters from observed lava flow morphologies. The shape of an inflated lava flow can change significantly over time. Therefore, incorrectly attributing the flow's final thickness to its dimensions in an initially fully molten state will yield excessively high flow rates, erroneous rheological properties, and unreasonably short eruption durations. To develop improved criteria for identifying inflated lava flows, we examined the McCartys lava flow field in New Mexico, USA. This locality provides an example of how pahoehoe-like lava lobes can coalesce and coinflate to form interconnected lava-rise plateaus with internal inflation pits. These structures were examined using a combination of field observations, low-altitude kite-based imaging, and quantitative geomorphology using high-resolution (1.47 cm/pixel) orthomosaics and stereo-derived digital terrain models. These observations were used to identify characteristics and diagnostics of inflation, thereby facilitating the interpretation of comparable landforms on other planetary surfaces. Lava-cooling models were also used to estimate the lava emplacement duration of the similar to 20-m-thick flows by demonstrating that the similar to 8-m-thick upper crust exposed within inflation clefts in the southern part of the McCartys lava flow field would have required 1.2-2.5 years of continuous lava supply to form. This places a minimum bound on the total eruption duration, and implies that comparably thick inflated flows on Mars required years to form. Plain Language Summary Lava is common throughout the solar system and can provide information about the geologic history of terrestrial planets and moons. However, reconstructing information about volcanic eruptions from lava flows requires an understanding of how their shapes change during an eruption. Much like an inflating balloon, or rising bread, lava can stretch and break apart as it grows. With lava, inflation is driven by the supply of molten lava into the flow's interior, which cools and adds new material to the crust, lifting the upper crust like a car jack. To accurately determine eruption conditions, it is necessary to rewind the inflation process and distinguish between the lava's initial shape and gradual changes that took place as the eruption progressed. To address this problem, we examined the McCartys lava flow field in New Mexico, USA, using hands-on observations and digital aerial photography-enabled by use of a camera mounted onto a kite. By mapping the three-dimensional shape of the lava and its structures, we determined that the 20-m-thick flow includes 8 m of crust and took about 2 years of continuous lava supply to form. This suggests that similar lava flows on other planets, like Mars, also involve eruptions that last for years.