The site in the northwest highlands where the important rocks were found. Image Prof Adrian Hartley
Scottish researchers have uncovered evidence of a previously unknown ice age during a supposed lull in the planet’s evolution.
Rocks unearthed from the north-west highlands of Scotland have caused quite a lot of excitement among scientists from the University of Aberdeen. Analysis of these rocks shows evidence of debris dropped from melting icebergs in lakes.
This is significant because the rocks have been dated to between 1,800m to 800m years ago, during a period dubbed the ‘boring billion’. This was coined by geologists to describe what was thought to be a relatively calm period in Earth’s evolution with little climatic upheaval.
However, this new discovery shows that this time may have included a previously undiscovered ice age.
“Throughout this so-called ‘boring billion’, the global climate was temperate and unchanged. Life was limited to algae in the ocean, the land was completely barren and oxygen was 10pc of what it is now,” said Prof Adrian Hartley, who led the study published in the Scottish Journal of Geology.
“Until now, no evidence for climate change had been discovered, but our study has shown there was ice at Earth’s surface during this period.”
Not such a boring billion after all
The discovery was made by analysing silty kale sediments that were billions of years old, allowing researchers to identify locations where pebbles had fallen from the icebergs and formed impact features on the lake floor. This, in turn, deformed even older layers of sediment.
While similar studies have helped researchers reconstruct the planet’s glacial history, this goes much further back in time when Scotland was at about the same latitude as South Africa is today.
“It’s the first evidence globally for glaciation at this time in Earth’s history – proving it wasn’t such a boring billion after all,” Hartley said.
This is not the first discovery in Scotland to significantly change the geological history books. In 2018, NUI Galway and University of Maine researchers found ancient sea shells in Scotland, which showed how quickly climate can change based on what was seen towards the end of the last ice age during the Younger Dryas era.
