## 1. Introduction

[2] A relationship proposed by *Pieri and Baloga* [1986] is now widely used in remote sensing to convert active lava flow area to lava volume flux. The relationship was first presented as a method for estimating lava volume flux for planetary lava flows by *Crisp and Baloga* [1990], and was subsequently adapted by *Harris et al.* [1997] to convert satellite-derived heat fluxes for active terrestrial lava flows to volume fluxes. The method was further adapted and applied to various effusive scenarios (basaltic, silicic, ′a′a, pahoehoe, fountain-fed, channel-fed, tube-fed) in a series of papers reviewed by *Harris et al.* [2007], with *Wright et al.* [2001] focusing on the application of the method to low spatial resolution (1 km pixel) satellite thermal data. *Wright et al.* [2001] concluded that the method operates by multiplying active flow area by a constant, the value of which is “*obtained from a crude approximation of the lava flow heat balance*”. Further, *Wright et al.* [2001] found that the method did not yield instantaneous effusion rates, but instead provided “*a valid and useful way to estimate average effusion rates from measurements of flow area*”. This was iterated by *Harris et al.* [2007] who used the term “time-averaged discharge rate” (TADR) to describe the output. TADR considers volume fluxes averaged over given time periods, so that the term TADR was thus adopted to stress the time-averaged nature of the output. Current consideration of the method culminated by *Dragoni and Tallarico*'s [2009] theoretically-based re-examination of the assumptions behind the original relationship of *Pieri and Baloga* [1986]. In spite of these treatments, the application of the conversion method when applied to satellite thermal data, and the necessary assumptions, remain a source of debate and confusion. This is apparent from *Dragoni and Tallarico* [2009] who argue that the underling assumptions of the original *Pieri and Baloga* [1986] model are not consistent with its use as a method for deriving TADR from satellite thermal data. However, a full consideration of the actual intent of the original *Pieri and Baloga* [1986] work, as well as the satellite-based approach of *Harris et al.* [1997], reveals why certain assumptions were used and remain valid today as approximations of realistic flow behavior. Consideration of field data reveal that the two main assumptions on which the method is based, i.e., that (1) TADR is related to flow length, and (2) lava surfaces cool in an essentially exponential fashion are, in fact, valid. Thus, to clarify the application of the method to low spatial resolution satellite data it is necessary to provide a full examination of the two original studies, as well as an assessment of their underlying assumptions using field data. Such a consideration shows that we rely on an empirical relationship whereby flow area is proportional to TADR under given insulation, rheological and ambient conditions.