Scientists use ice-core samples and soil samples, drilling down deep, to discover what was happening on the earth millions and millions of years ago. But about 1 billion years ago something strange happened, scientists can't find the data. Geological samples go from about 550-million-year-old rocks to layers of 1.7 billion-year-old rocks sitting atop each other. Now, scientists think they've discovered the missing discrepancy.
Previously, there were two theories about what happened before the Neoproterozoic era. "One suggests that tectonic activity associated with the assembly and breakup of the supercontinent Rodinia created the Unconformity, while another points to erosion from widespread glaciation during our planet’s 'Snowball Earth' phase some 700 million years ago," the report said.
But a postdoctoral researcher in earth sciences led a team at Dartmouth College in looking at glacier movement, which could account for the missing links in fossils and rock samples.
According to Kalin McDannell and his team, "Something really unique was going on in terms of global geodynamics and surface processes that allowed the Great Unconformity to both form and then be preserved. That’s my perspective on why this has captured people's imaginations."
There was obviously tectonic activity in the Rocky Mountains and the Ozark Plateau, but he increased the samples to look at areas of North America that didn't have a lot of tectonic activity. Examining rocks from East Lake Athabasca in Saskatchewan, Canada and the Minnesota River Valley, the team found evidence of rocks cooling with glacial erosion all at the same time.
"Imagine taking the very middle of the U.S. today, and then just eroding kilometers of that in the span of a geologically short period of, let's say, 60 to 100 million years," said assistant professor C. Brenhin Keller, who did another study in 2019 that showed consistencies with McDannell's. "That's not normally what happens. If those kinds of erosion rates were normal, we would have no crust that was older than a few hundred million years."
The next step for the team is looking at samples from more locations all over the world from the same time to get a bigger picture of what was happening on the earth 1 billion years ago.