Effusion rate controls on lava flow length and the role of heat loss: a review
Published:January 01, 2009
A. J. L. Harris, S. K. Rowland, 2009. "Effusion rate controls on lava flow length and the role of heat loss: a review", Studies in Volcanology: The Legacy of George Walker, T. Thordarson, S. Self, G. Larsen, S. K. Rowland, Á. Höskuldsson
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Walker (1973; Phil. Trans. R. Soc. Lond., 274, 107) argued that, for a limited set of compositions and flow types, effusion rate (E) was the principal influence on flow length, sparking a series of studies into the volume and cooling limits on flow extension. We here review these works, as well as the role of heat loss in controlling flow length. We also explore the applicability of Walker's idea to a larger compositional and morphological range. Heat loss plays a fundamental role in determining flow core cooling rates, thereby influencing cooling-limited flow length. Field measurements allow classification of four flow types with respect to heat loss. In this classification as we move from poorly insulated to well insulated regimes, decreased heat losses increase the length that a flow can extend for a given E, composition, morphology, or amount of cooling: (1) immature tube-contained, basalt - thin tube roofs provide minimal insulation, allowing cooling rates of c. 10−2 °C s−1 so that at low E, these flows extend only a few hundred metres; (2) poorly crusted, basalt - open channels with hot surface crusts also exhibit cooling rates of c. 10−2 °C s−1so such flows extend a few kilometres at E < 1m3 s−1; (3) heavily crusted, da-cite - heat losses are reduced when thick crusts form, reducing core cooling rates to c. 10−4 °C s−1 so these flows can potentially extend several kilometres even at low E and despite very high viscosities (109−1010 Pa I); (4) master tube-contained, basalt - thick tube roofs insulate flow, reducing heat losses and cooling rates to c. 10−3 °C s−1. These cooling rates mean that at low BE, tube-contained flows can extend tens to hundreds of kilometres. Basically, if composition, insulation, and morphology are held constant flow length will increase with effusion rate.
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Studies in Volcanology: The Legacy of George Walker
Professor George Patrick Leonard Walker was one of the fathers of modern quantitative volcanology and arguably the foremost volcanologist of the twentieth century. In his long career, George studied a wide spectrum of volcanological problems and in doing so influenced almost every branch of the field. This volume, which honours his memory and his contributions to the field of volcanology, contains a collection of papers inspired by, and building upon, many of the ideas previously developed by George. Many of the contributors either directly studied under and worked with George, or were profoundly influenced by his ideas. The topics broadly fall under the three themes of lava flows and effusion, explosive volcanism, and volcanoes and their infrastructure.