While tectonic stretching from the Tharsis Bulge created the primary structural foundation of the canyon system, volcanic activity played a significant role in modifying its internal geometry. As the crust underwent tension, massive fissures formed, but subsequent volcanic eruptions heavily influenced the final landscape.
Large scale lava flows frequently filled the lower sections of the valleys. This process of infilling can mask the original tectonic floor and create flat-bottomed valley profiles. In some regions, these volcanic deposits acted as a sealant, effectively smoothing out the rugged terrain created by the initial crustal extension. Furthermore, some lava flows may have been channeled through existing fractures, creating secondary features such as collapsed tubes or modified wall profiles.
Therefore, the internal geometry is a complex combination of tectonic rifting and volcanic modification. The canyons are not just simple cracks in the crust but are layered geological features where volcanic material has redistributed volume within the valley walls and floors. This interaction between tectonic forces and volcanic resurfacing is essential to understanding the multifaceted evolution of the Martian landscape.
