give a brief summary

Before the creation of man, the Great Spirit (whose tracks are yet to be seen on the stones, at the Red Pipe, in the form of a large bird) used to slay buffaloes and eat them on the ledge of the Red Rocks, on top of the Coteau des Prairies, and their blood running on to the rocks, turned them red. One day when a large snake had crawled into the nest of the bird to eat his eggs, one of the eggs hatched out in a clap of thunder, and the Great Spirit, catching hold of a piece of the pipestone to throw at the snake, moulded [sic] into a man. This man's feet grew fast in the ground where he stood for many ages, like a great tree, and therefore he grew very old; he was older than a hundred men at the present day; and at last another tree grew up by the side of him, when a large snake ate them both off at the roots, and they wandered off together; from these have sprung all the people that now inhabit the earth.

Before the creation of humans, there was a Great Spirit who used to slay buffaloes and eat them on the ledge of the Red Rocks. The blood of the buffaloes turned the rocks red. One day, a snake crawled into the bird's nest to eat its eggs. When one of the eggs hatched with a clap of thunder, the Great Spirit molded a man out of a piece of pipestone to throw at the snake. The man's feet rooted into the ground and he grew very old. Eventually, a tree grew beside him and they were both eaten by a snake. From them, all the people on Earth descended.

In summary, before humans existed, the Great Spirit used to hunt buffaloes and eat them on a ledge of Red Rocks, where their blood turned the rocks red. One day, a large snake crawled into the nest of the Great Spirit's eggs, leading to one of the eggs hatching with a loud noise. The Great Spirit, trying to defend the eggs, grabbed a piece of pipestone and accidentally molded it into a man. This man's feet were rooted in the ground and he stood like a tree for a very long time, growing very old. Eventually, another tree grew beside him, but they were both eaten by a large snake and they wandered off together. From these two beings, all the people that now inhabit the earth are said to have come from.

The passage you provided is a brief summary of a creation story or myth. It explains how, before the existence of humans, the Great Spirit was a bird-like creature that used to slay buffaloes and eat them on top of the Red Rocks, which caused the rocks to turn red from the blood. One day, a snake intruded into the bird's nest to eat its eggs, and in the ensuing encounter, the Great Spirit molded a piece of pipestone into a man. This man's feet became rooted in the ground like a tree, making him live for a very long time. Eventually, another tree grew beside him, but they were both eaten by a snake at the roots and traveled together. From them, all the people on earth are said to have descended.