For billions of years, the Earth did not have enough oxygen in the atmosphere to support most of life as we know it today. Then about 2.3 billion years ago, something dramatic happened. Tiny cyanobacteria had appeared and were producing oxygen through photosynthesis. Once the oceans and land had absorbed all they could, excess oxygen went into the atmosphere – wiping out anaerobic organisms and setting the stage for the evolution of plants and animals.
In Part 4 of the Columbia Geology Tour, David Walker of the Lamont-Doherty Earth Observatory explores the source of the red sandstone of Russell Hall at the Columbia Teachers College on 120th Street. Russell is one of the stops on Walker’s informal geology tours of the Columbia University campus.
Coming next week: Evidence of orogeny and a lesson in how rock flows, in the lobby of the Northwest Tower. (You can watch all of the videos on YouTube here.)
