Unusually long lava rises occur in the distal portion of the Toomba basalt flow, up to 120 km from the source. In the Lolworth creek region, three parallel lava rise ridges occur over a 6 km section. Two of these ridges are continuous for the entire 6 km. The ridges average 7 m in height and range from 35 m to 300 m in width. Lava inflation clefts are numerous, and lava rise pits also occur. Down flow, a single lava rise ridge, averaging 18 m high and up to 500 m wide, extends for a further 10 km. This ridge has a generally level surface with abrupt edges sloping between 45¿ and 90¿. Accurate surveys across the ridges show that in some cases there has been some stretching of the surface, presumably prior to the formation of the prominent clefts. The ridges were formed from an initially thin flow that was inflated by a continuous layer of lava that underlay almost the entire width of each ridge, rather than by a system of lava tubes of more limited dimensions. Inflated material represents over 90% of the volume of the distal parts of the flow. Estimates of the time required to inflate the lava rise ridges range from 60 days to a year. ¿ 1998 American Geophysical Union