Hebes Chasma is a large, closed canyon entirely isolated from the others. Thus the Martian canyons had a complex origin, with faulting and subsidence common in the west and fluvial effects common in the east. The most intriguing aspects of the canyons are the presence of thick stacks of layered sediments. They are most common in the Hebes, Ophir, and Candor chasmata. The only explanation is that these sediments were deposited under water.
Geologists think that standing bodies of water partly filled the canyons in past times.
These lakes were probably fed by water seeping from the canyon walls. Some geologists say that the lakes at Candor and Ophir chasmas were released catastrophically as the ridge dividing Candor Chasma from the main canyon to its south failed. To the east, the canyons' flat floors become rugged, and their linear walls become inward-facing cliffs enclosing areas of chaotic terrain. The chaotic debris consists of blocks that look as though broad areas of the former surface collapsed. Large channels extend out of these chaotic areas and extend thousands of kilometers northward across Chryse Planitia until they merge with the low-lying plains at high northern latitudes.