The formations we are looking at out here in the Mojave Desert have drawn countless geologists because they tell a story of early Earth. The time periods represented here span from the late Precambrian Era about a billion years ago to the early-mid Cambrian Period, about 500 million years ago.
The Precambrian Era represents approximately the first 90% of earth's history. During this time, Earth was a pretty hostile place, and yet life began! It was dominated by single-celled organisms, but through processes like photosynthesis, they transformed our planet into a much more habitable place. This makes us wonder about other planets with hostile environments and what could live and thrive there. Here's my students' take on the Precambrian Era:
In the stratigraphic column below, each horizontal layer represents a deposit of sediment, with the oldest layers at the bottom and youngest layers at the top.
Stratigraphy of this area, courtesy of NASA's Astrobiology Institute
We began our explorations in a layer of rock that’s not on this chart, in the Beck Spring formation. It’s below the Kingston Peak formation and is about a billion years old! The oldest layers of sedimentary rock are going to be on the bottom layers, so all we have to do is climb UP in order to “travel through time”.
Tyler at the Beck Springs formation.
Me, taking some field notes at the Beck Springs formation.
Here's a video I made for you to explain some of the rock samples we were looking at:
Snowball Earth
The Kingston Peak formation is the next layer (slightly more recent) and represents a dramatic time in Earth’s history known as “Snowball Earth”. There’s a lot of evidence of widespread glaciation, including glaciers near the equator. Scientists think that there was so much of the sun’s radiation reflected back into space from this time that the Earth would’ve been super-chilled. Geobiologists and astrobiologists are intrigued by questions surrounding these Snowball Earth events: What caused this cooling period? What exactly were the environmental conditions like? What life forms could have survived this event? How did these changes in the environment influence the distribution of species? We look to younger layers in the rock to help us answer these questions- I’ll show you that tomorrow!
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