Lava Beds National Monument Butte is just outside the boundary of the monument, the Callahan flow is in Lava Beds and is the youngest flow in the monument. Spatter cones are built out of thicker lava. The lava is thrown out of the vent and builds, layer by layer, a chimney surrounding the vent. Fleener Chimneys and Black Crater are examples of spatter cones. Roughly ninety percent of the lava in the Lava Beds Monument is basaltic. There are primarily two kinds of basaltic lava flows: pahoehoe and 'a'a. Pahoehoe is smooth, often ropy and is the most common type of lava in Lava
The Barrier ponded, eventually cooling to form an ice-marginal lava flow. When the ice melted away, the ice-cooled lava-flow front formed a precipitous cliff; water ponded behind the lava dam, forming Garibaldi Lake. The unstable lava formation of The Barrier has in the past unleashed several debris flows in the area below Garibaldi Lake. The most recent major landslide in 1855-1856 formed a large boulder field which gives Rubble Creek its name. At least of rock was removed from The Barrier during the 1855-1856 event. Concerns about The Barrier's instability due to volcanic, tectonic, or heavy rainfall activity prompted the provincial government