Icebox or hothouse?
By observing other stars, we think that the Sun’s luminosity has increased by 25 percent since its formation. Thus, the early Earth must have received less sunlight, and should have been covered with ice. While there is evidence of periodic Ice Ages early in the Precambrian, they were not lengthy. One possible reason why the Earth did not become an icebox is that the early atmosphere had a high concentration of greenhouse gases, particularly carbon dioxide. These served as an insulating blanket, keeping the surface warm.
Topic: Earth Science
Keywords: Glacial epoch, Greenhouse effect, Atmospheric, Greenhouse gases, Paleoclimatology, Solar radiation
This 2.3-billion-year-old outcrop of the Bruce formation contains evidence of a very early Ice Age.
The broken-up rock fragments in this conglomerate from the Gowganda formation are not in contact with one another.
Behind these samples is a cast of an outcrop from the Gowganda formation, made up of fine layers of sediment.