From the Hadean, Archean, and Precambrian to the Phanerozoic, which includes the Paleozoic, Mesozoic, and Cenozoic, these are the most significant historical and geological events in the history of Earth. Research carried out by Andrej Spiridonov, a geologist at Vilnius University, has based its study on the postulates of the International Commission on Stratigraphy. By studying conodonts, ammonoids, graptolites, and calcareous nanoplankton, he has discovered that our planet’s timeline is more complex than previously known. Read on to find out more.
Transitions between geological chapters
Due to a recent study, events geologists use to distinguish transitions between geological chapters in Earth’s story follow a unknonw hierarchical pattern, one that might shed light on both past and future tumult.
“Geological time scales may look like tidy timelines in textbooks, but their boundaries tell a much more chaotic story,” says study co-author Andrej Spiridonov, a geologist and paleontologist at Vilnius University in Lithuania.
In addition, Spirdonov explains that their findings show that what seemed like uneven noise is actually a key to understanding how our planet changes, and how far that change can go.
The history of our planet: full of upheavals
The history of our planet is replete of upheavals, some dramatic enough to trigger the entire new blocks of geological time. This includes modifications between comparatively short divisions like ages and epochs, as well as much longer units of time like eras and eons.
The asteroid that decimated the dinosaurs 66 million years ago, as an example, caused enough overall disruption to conclude the Mesozoic Era and end up the Cenozoic. The Cenozoic, which continues currently, is further subdivided into three periods and at least seven epochs. The processes driving these transitions are difficult, yielding variable intervals of relative stability punctuated by apparently unkonwn calamities of several types and magnitudes. Yet there are signals this may be less capricious than it seems.
On what the recent study focuses on
The recent investigation focuses on the current Phanerozoic Eon, which dates back around 540 million years and takes into account the Cenozoic, Mesozoic, and Paleozoic eras. It’s one of Earth’s four eons so far, preceded by the Proterozoic, Archean, and Hadean.
Spiridonov and his colleagues used time divisions established by the International Commission on Stratigraphy, but also studied boundaries based on stratigraphic ranges of marine animals and on ancient taxa such as conodonts, ammonoids, graptolites, and calcareous nanoplankton. The boundaries between time units steday formed intriguing clusters, they found, separated by lengthy spans of relative calm.
What uneven distribution suggests
“The intervals between key events in Earth’s history, from mass extinctions to evolutionary explosions, are not scattered completely evenly,” Spiridonov says. “They follow a multifractal logic that reveals how variability cascades through time.”
Based on their findings, they conclude this span is at least 500 million years. “If we want to understand the full range of Earth’s behaviours, whether periods of calm or sudden global upheaval, we need geological records that cover at least half a billion years. And ideally, a billion,” Spiridonov says. Studying shorter time scales may fail to convey the extremes our planet is capable of producing, the researchers warn.
