Volcanism on Earth’s Seafloor and Venus

Abstract

The surface of Venus, obscured by dense cloud cover, is similar in many ways to the seafloor that lies hidden beneath the deep waters of Earth's oceans. Although both are difficult to observe, decades of research indicate that each surface is dominated primarily by basaltic volcanism. This is not surprising as Earth and Venus are similar in size, bulk density, and position in the solar system, and the probability of similar elemental abundances and internal heat sources implies corresponding similarity between their interior melting, magma production, and surface volcanism. Even though Earth's seafloor and Venus are dissimilar in many ways, both environments are characterized by significantly elevated pressure at the surface resulting, respectively, from the burden imposed by the overlying ocean water and the weight of the dense atmosphere. This provides volcanologists with an excellent opportunity to examine how elevated surface pressure affects the development and behavior of volcanic systems. We begin this chapter with an overview of the types of data collected to date that reveal the surfaces of the seafloor and Venus, then summarize what is known about the environmental conditions at or near each surface. In addition, since comprehensive reviews are presented elsewhere (e.g., Venus: Head et al., 1992, and Crumpler et al., 1997; seafloor: Fornari and Embley, 1995, and Chadwick and Perfit, 1998), we provide only a brief overview of the volcanic styles observed in each setting so as to establish a context within which to consider the behavior of several specific volcanic processes and features. The bulk of the chapter focuses on four "case study" examinations of how the high-pressure environments of Venus and the seafloor specifically affect intrusive processes (l: magma stalling related to neutral buoyancy), effusive eruptions (2: formation of small to intermediate volcanoes; 3: emplacement of large larva flows), and explosive events (4: pyroclastic eruptions). These detailed presentations serve to illustrate the similarity between key volcanic styles observed on Venus and Earth's seafloor, and help demonstrate the role played by the near-surface, high-pressure environment present in both settings. Environmental Effects on Volcanic Eruptions: From Deep Oceans to Deep Space.