(Marker #1)WelcomeLAVA RIVER CAVE is one of Oregon's longest (5466 feet) uncollapsed lava tubes.About 100,000 years ago, this conduit carried 2000° F. (1100° C.) lava from an upslope vent to lower areas on the flanks of the Newberry Volcano.The long trench you are standing in formed after the lava drained from the tube and part of the cave roof collapsed."Breakdown", or collapse blocks, litter the first 1000 feet, but beyond lies nearly a mile (actually 4400 feet) of cave, much of it appearing as it did when the ancient lava river left it.(Please leave the cave clean so others can enjoy it.)
(Marker #2)Highway Crossing, Flow Lines and Lava ShelfHighway CrossingAt the bench-look both ways you are now crossing US 97! The ceiling is about 31 feet above you and the roof thickness is about 50 feet.Flow Lines and Lava Shelf"Bathtub rings" or flow lines form when lava maintains a constant level and deposits a ridge of lava on the wall. The more prominent ridge is called a lava shelf and has lavacicles (lava stalactities) on its underside due to remelting of the tube surface. A thin glassy glaze, wrinkled glaze, and other remelt features are abundant in the cave.
(Marker #3)Tube in Tube"Tube in tube" or vertically stacked passages. Lava here eventually drained only through the lower tube as lava levels lowered late in the eruption. Look for the surfaces and flow fronts of the last flows throughout the cave.
(Marker #4)Sand GardensSediment washes slowly through roof cracks and partially fills the cave, especially in the lower section. The delicate "sand garden" or "fairy castles" form as water droplets erode the sand fill.SAND FILL NEAR THE END OF THE CAVEThe cave sediment thickens and eventually fills the tube from floor to ceiling. Two enthusiastic explorers dug a trench over 300 feet long in 1936, but they were unable to extend the length of the open cave.