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
Lava Creek Tuff Lava Creek Tuff The Lava Creek Tuff is a tuff formation in Wyoming, Montana and Idaho, United States, created during the Lava Creek eruption around 630,000 years ago, which formed the Yellowstone Caldera. The Lava Creek Tuff is distributed in a radial pattern around the caldera and is formed of of ignimbrites. The tuff has been exposed by erosion at Tuff Cliff along the Gibbon River. Lava Creek Tuff ranges in color from light gray to pale red in some locales. Rock texture of the tuff ranges from fine-grained to aphanitic and is densely welded. The maximum thickness of the