Land rising above the sea 2.4 billion years ago transformed Earth’s life, climate

The University of Chicago, bang that Shales sampled from around the world contains archival-quality evidence of passing, almost indiscernible hints of rainfall that caused weathering of land as old as 3.5 billion years ago. The exposure of new land to weathering may have set off a series of glacial episodes and atmospheric changes spawned by the Great Event, in which free oxygen filled the air. The Natural signatures in shale rocks, a consolidated form of mud, point to an increased rate in the rise of land above the ocean 2.4 billion years ago—possibly triggering dramatic changes in climate and life.

The revelation of novel land to weathering may have set off a series of glacial episodes and atmospheric changes spawned by the Great Oxygenation Event, in which free oxygen filled the air

The suggestion is from analyses of three oxygen isotopes, particularly the rare but stable oxygen-17, in multiple shale samples from every continent and spanning 3.7 billion years of Earth's history. Shale rocks are formed by the weathering of crust, so "they tell you a lot about the exposure to air, light and precipitation, and the 

Prominent deviations in the proportions of oxygen-17 and 18 with more common oxygen-16 allowed scientists to read the chemical history in the rocks. In doing so, they were able to launch when the pattern of sleet on continents switched from near-coastal to more inland, reflecting the transport of moisture over vast swaths of emerged lands as the continents rose above seawater and high-mountain ranges and plateaus were created.