Seafloor shallowing in the early Earth: Implications for the evolution of the surface environment and the origin of life
Abstract
The surface environment in the early Earth defines physical and chemical conditions pertinent to the origin of life. Although it is likely that continents were already present, the specifics of the surface environment, such as the amount of exposed landmass, are poorly known. An important yet often overlooked component in this discussion is the oceanic lithosphere. Several aspects of the lithosphere, such as bathymetry and subsidence rate, acquire special importance in the early Earth because they control the extent of subaerial landmasses on which prebiotic compounds may accumulate. Because these factors depend on the thermal structure of the suboceanic mantle, in this study, we investigate the evolution of oceanic lithosphere in the early Earth and its relationship to the surface environment through numerical modeling. Whereas at present-day seafloor subsidence slows down at 70-80 Myr of age in response to the onset of sublithospheric convection, we show that in the early Earth, higher radiogenic heat production could have halted subsidence and even induced seafloor shallowing. In the presence of hotspot volcanism, such shallowing could have resulted in long-lived subaerial land in the form volcanic islands and resurfaced seamounts. As our models also indicate continents were underwater prior to 3 Ga, these islands were likely the only exposed landmasses throughout most of the Archean, being the sole locality for warm little ponds, in which prebiotic chemistry could have thrived through seasonal wet-dry cycles.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMPP53B..07R
- Keywords:
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- 1041 Stable isotope geochemistry;
- GEOCHEMISTRY;
- 1626 Global climate models;
- GLOBAL CHANGE;
- 5225 Early environment of Earth;
- PLANETARY SCIENCES: ASTROBIOLOGY