Controls on the Hydrological and Topographic Evolution of Shield Volcanoes and Volcanic Ocean Islands

Abstract

Volcanic ocean islands and shield volcanoes form superb natural experiments for investigating changes in topography and hydrology over geologic time. As volcanoes age, their surfaces evolve from un-dissected, highpermeability landscapes into deeply dissected, low-permeability terrain. Here we review the tight links and co-evolution of topographic and hydrologic processes in volcanic landscapes. We discuss a number of factors that affect rates and patterns of hydrological and topographic co-evolution, including soil development, spatial and temporal variability of water availability, flank collapses, geologic architecture, and the tectonic history of subsidence or uplift. To illustrate the effects of climate on volcanic dissection, we compile a global dataset of volcanic landscapes and ages that suggests that substantial dissection begins between 0.5 and 2 million years after construction, with volcanoes in high-precipitation regions tending to become dissected more quickly than those in drier regions. Obtaining a deeper understanding of volcanic landscape evolution will require further research on several topics, such as the sensitivity of river incision to fluctuations in precipitation, the hydrologic responses of soil to chemical weathering and dust deposition, the evolution of chemical and physical erosion rates over a volcano's lifetime, the role of hydrology in triggering of flank collapses, and the extent to which the long-term evolution of an island is determined by the initial and boundary conditions set by geologic structure and regional tectonics.

Exploring Hawaiian long-term insular geodiversity dynamics

“…For example, on a relatively stable spur thicker soils may develop over time, while active steep slopes or ravines may only host shallow soils. For young volcanic islands, vegetation affects soils through the dominance of pioneer plants, while on aging islands the organic matter production, has more pronounced effects on soil formation (Jefferson et al 2014). Although debated in some publications, the effects of mega landslides (McMurtry et al 2004), could be considered, as landslides have certainly stripped the soils and strongly affected the topography of many Hawaiian Islands and, in that way, contributed to setting back soil formation.…”

“…The increase in hydrological diversity in older islands has several reasons. River development on younger islands is hampered by active infill or cover by lava flows (Jefferson et al 2014) and other volcanic deposits. The initial porosity of most volcanic deposits on the younger islands is relatively high, which suppresses rapid hydrological development.…”

“…While these hypotheses seem to successfully explain elements of the spatial and temporal distribution of biodiversity on islands (MacArthur and Wilson 1967, Warren et al 2015, Whittaker et al 2017), they do not explicitly address (components of) geodiversity and its dynamics. To illustrate the importance, the complex interactions and co-evolution of topography and hydrology on the evolution of oceanic island landscapes has been reviewed in a study by Jefferson et al (2014), who concluded that dissection of volcanic landscapes typically begins 0.5-2 Ma after eruption of the last lavas that form the main shield.…”

“…The effect on the landscape also sets back time-related processes such as weathering, soil formation, fluvial incisions and therefore, general geomorphological landscape development. In the accretion phase, active volcanic islands develop on top of the oceanic crust and grow in elevation, and often emerge above sea level as shield volcanoes, which are characterized by relatively low-angle slopes (Jefferson et al 2014). Elevation increases with magmatic additions until the mantle plume is disconnected Fig.…”

“…Such controls on the hydrological and topographic evolution of shield volcanoes and volcanic ocean islands were studied by Jefferson et al (2014), who concluded that topographical younger islands such as the typical shield volcano topography of Hawaii, have higher elevation and area, but have lower mean slope angle values. The spatial distribution of surface hydrology is presented in the location map (Fig.…”