328 LAVA pile of thousands of flows, and the individual flows may be more than several tens of metres thick The individual flows may extend for hundreds of kilometres How can such huge lava flows be emplaced? The old idea for the emplacement of flood basalts was that these flows were emitted at incredible velocities However, based on the detailed survey of the structure of flood basalts, geologists arrived at an alternative idea that these flows are emplaced by slow movement, with most of the great thickness being achieved by injecting lava into the interior of an initially thin flow (see Large Igneous Provinces) The most famous example of a flood basalt is the Deccan Traps of central India, where about 000 000 km3 of basaltic lavas were erupted within a half million years at the end of the Cretaceous The Siberian Traps, which erupted in Permian–Triassic times, are much larger than the Deccan Traps but less well understood Many scientists consider that the volcanism that produces flood basalts is related to the rise of hot mantle plumes The origin of the flood basalts is closely associated with entire-mantle dynamics, and their magma genesis is one of the currently popular topics in Earth science Lava Flow Hazards Figure (A) Columnar jointing in thick basaltic lava from Miyakejima, Japan (B) Tabular jointing in the middle Pleistocene andesitic lava of Utsukushigahara, Japan (Photographs supplied by T Oikawa) flow The brittle cooling margin at the base of the lava flow is dragged by the still-mobile magma inside the flow, and fractures parallel to the flow are formed Shear deformation occurs at the bottom of the flow Platy jointing is commonly observed in silicic lava flows such as those composed of andesite or dacite Flood Basalt At certain times in the geological record, prolonged volcanic activity of immense scale resulted in thick piles of numerous basaltic lava flows that covered thousands of square kilometres (similar flows of the intermediate, more siliceous, lava type phonolite are also known in East Africa) The large-volume basaltic lava flows are called ‘flood basalts’ or ‘plateau basalts’ The total volume of a flood-basalt eruption may sometimes exceed 100 000 km3, and this huge volume is erupted over a short time interval, usually less than Ma Flood-basalt sequences consist of a Lava flows destroy or ignite all things in their path When lava invades developed areas, it can be disastrous In the cases of many volcanoes, the people living nearby make great efforts to stop the advance of lava flows, but much land and many buildings are destroyed and buried by lava flows Fortunately, the speed of advance of a lava flow is, usually, very slow, and in many cases people can escape from it Kilauea (Hawaii, USA) Kilauea is one of the most active volcanoes in the world More than 90% of the land surface of the Kilauea volcano has been re-covered by new lava within the last 1500 years In particular, the southeastern flank of the east rift zone of Kilauea has been threatened frequently by lava flows, and more than 30% of the land surface between the east rift zone and the coast has been covered by lavas since 1955, less than half a century ago (Figure 6) The Puu Oo–Kupaianaha eruption of Kilauea from 1983 to the present (2004) is the longest duration of a single eruption in the historical record Lava flows from the Puu Oo and Kupaianaha craters spread widely on the southern flank of the east rift zone and poured down to the ocean Lava frequently changed direction, and one of the flows invaded Kalapana village in 1990 By the end of October that year, lava had destroyed all of Kalapana and