River of Rocks - The Devils Homestead Lava Flow

River of Rocks - The Devils Homestead Lava Flow. . At some time within the last several thousand years, an eruption of magna from the bottom of the earth crust sent a broad stream of hot liquid rock across this land. The flow started to your right, 3.2 kilometers (2 miles) south of here at the site of a spatter cone formation known as a Field of Chimneys. When the eruption stopped, the lava cooled and hardened into its present form, but how did it look like a river of rocks?, Pahoehoe lava began flowing downhill toward Tule Lake to your left. It was very hot (1200°C), but cooling and loss of gas began right away. As the flow crept along the outer several inches solidified into a hard layer. Under stress from the still liquid and very mobile flow interior, the lava crust broke repeatedly, forming a jumble of frothy-looking plates that were rafted along like blocks of ice on a river., By the time the flow reached here, cooling and loss of gas had transformed it into a rough cinder-like lava called aa., Pahoehoe lava (pah-HOY-hoy) , a hot, gas rich, low viscosity basalt. , Aa lava (AH-ah) , a cooler, less gaseous, higher viscosity basalt.