Weathering at Purgatory Chasm

Oxidation: Many of the larger rocks show signs of oxidation. This means that the metallic elements are reacting with oxygen. Streaks of orange-red color appear on the surface of the rocks showing the chemical change of Iron to Iron-oxide from the process of oxidation.

Organic acids: On each side of the chasm moss and lichen grow onto the rock, corroding away material with acid they create.

Ice wedging: As shown by the picture, there is constantly ice getting stuck in the chasm and it has over time cracked the rocks on the bottom of the chasm into smaller pieces. In fact there is a large rock split in two named “Fat Man’s Misery” that is believed to be formed by ice wedging.

Root wedging: Root wedging is quite common in Purgatory Chasm. Trees from above the chasm on either side have grown long roots that have stretched deep into the rock walls, prying through layers of rock and breaking off large portions of rock from the sides of the chasm. Each tree has wedged many different roots into the chasm.

Exfoliation: On the top of one side of the chasm, to the right when looking at the chasm from the entrance, large sheets of rock are seen sliding off one another in layers. Once the chasm was created the pressure on these rocks decreased tremendously, allowing for the pressure of the rocks that had been keeping the rocks from collapsing to burst forward. With no pressure to counteract the rocks, layers of the rock broke off from the rest and slide slightly from their original placement .

Abrasion: Along the sides of the chasm large striations can be seen. There are some jagged angles near the top of the chasm that could not have been affected by abrasion but lots of rocks lower down in the chasm have been rounded off with polished surfaces that could only have formed by weathering over time. These rocks look noticeably smoother than other rocks above the chasm.