Eos Chaos may be made of layer after layer of lava flows, probably mixed with deposits of volcanic ash that fell out of the air following big eruptions. It is likely the rock strata in the walls preserve a long geological history of Mars. Dark layers may be due to dark lava flows. The dark volcanic rock basalt is common on Mars. However, light-toned deposits may have resulted from rivers, lakes, volcanic ash, or wind blown deposits of sand or dust. The Mars Rovers found light-toned rocks to contain sulfates. Probably having been formed in water, sulfate deposits are of great interest
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