Researchers from Georgia State University’s Geosciences Department are using mineralogical tools to study climate change in East Africa that dates back nearly 1.9 million years ago.
“Doing this research is exhilarating because you get a glimpse into how dynamic environmental change is on Earth,” said geosciences chair and Professor Daniel Deocampo, who is leading the research project. “We are able to see how the landscapes we see today have not always been that way and are a big part of what gave rise to humans.”
To understand the effects of climate and environmental change on human evolution, the researchers examined the chemical composition of clay minerals in lake sediments at Olduvai Gorge, Tanzania. The researchers use X-ray diffraction, funded by the National Science Foundation, combined with electron microprobe analysis performed by colleagues at Rutgers University to analyze the materials and determine when the lakes were fresh versus saline. A fresher lake can in some cases indicate instances of humidity.
Deocampo believes that these findings provide a premise for understanding the percentage of modern-day environmental change that is natural versus human-caused.
“Changes in the Earth’s climate are really driven by changes in the Earth’s orbit,” he said.
“Things like the arrival of sunlight and solar radiation are also related to changes in the Earth’s orbit. To go back a couple million years in Earth’s history and find evidence that the environment changes according to changes in Earth’s orbit is really solid evidence that we know what’s happening.”
The researchers identified six episodes in the climate history of East Africa where there were signs of increased humidity. Of the six, five match up exactly with known changes in the Earth’s orbit.
“This research gives us the time scale that natural climate change occurs over,” said Deocampo. “The dramatic environmental changes that occurred in the past happened over a 10,000 year timespan. Today it’s occurring at a faster rate, so it reinforces how dramatic the modern environmental change that humans are causing really is.”
The study, “Whole-rock Geochemistry Tracks Precessional Control of Pleistocene Lake Salinity at Olduvai Gorge: A Record of Authigenic Clays,” will be published in the August issue of Geology.