INTRODUCTION TO SPECIAL SECTION - LONG LAVA FLOWS

Long lava flows are traditionally considered to form when low-viscosit y lava is erupted at high effusion rates. However, this view has recen tly been challenged. Detailed field measurements on active lava flows on Kilauea have shown that inflation of lava flows after emplacement c an result in reactivation and continued lengthening of flows. Inflated sheets can thus act a insulated conduits (lava tubes) that permit the transport of lava over great distances at near isothermal conditions. Detailed observations of long lava flows in the Columbia River Basalt Group and in the Cenozoic Volcanic Provinces in northern Queensland c onfirm that this mechanism is not restricted to recent flows on Hawai' i. These findings have led to a search for evidence of inflation in fl ows in other parts of the world and have stimulated theoretical and la boratory research on the emplacement and cooling of lava in flows and in tubes. Understanding the formation of long submarine and planetary lava flows presents an additional challenge. Current evidence supports high effusion rates for some, possibly all, long planetary lava flows , and improved resolution from the Mars Global Surveyor will undoubted ly lead to either a confirmation or a rejection of this view. In this review, we discuss the geological importance and distribution of long lava flows, we investigate diametrically opposed views on the formatio n of long lava flows, and we stress the need for an interdisciplinary approach to improve our understanding of these enigmatic geological fe atures.