Major, Early Volcanism on Terrestrial Planets
Paul K. Byrne
Affiliations: 1Department of Earth, Environmental, and Planetary Sciences, Washington University in St. Louis, St. Louis, MO 63130, USA; 2McDonnell Center for the Space Sciences, Washington University in St. Louis, St. Louis, MO 63130, USA.
Presentation type: Poster
Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall
Poster Board Number: 240
Programme No: 1.4.5
Abstract
The earliest preserved crust on Mercury is about 4.2 billion years old. The apparent lack of surface materials predating this point is attributed to resurfacing from some combination of major bolide impacts and volcanism. At present, about 27% of the surface of Mercury is occupied by "smooth plains" terrain, the majority of which is thought to be flood lava flows. Most of the remainder of the surface is covered in "intercrater plains"; these units, although much more cratered than the smooth plains, are also predominantly volcanic, also emplaced as flood lavas. The geological record of Mercury thus indicates that the planet's crust was rapidly built following the magma ocean phase, with eruptive rates and fluxes rapidly waning even before the planet entered a state of global contraction. On Mars, the oldest preserved crustal materials are interpreted to comprise reworked volcanic sediments, implying an even earlier phase of major crust-building by flood-mode volcanism. Even on the Moon, where recognised volcanic activity is primarily restricted to giant impact basins, basaltic lavas were being erupted on the lunar farside as early as 4.2 billion years ago. There is no identified ancient crust on Venus, and the earliest markers of volcanic activity on Earth are detrital zircon crystals. Nonetheless, by comparison with Mercury, Mars, and even the Moon, it is likely that the very earliest eras of Venus and Earth following magma ocean solidification were characterised by eruptive fluxes unlike anything that remains on the surfaces of any of these worlds today.