
Iceberg calving from a Greenland glacier can carry rocks to distant coasts
Professor Ross Mitchell
The rocks transported by icebergs from Greenland to Iceland add to evidence that the European climate became much colder for a century or two in 540 AD.
This cold season in the Northern Hemisphere has been shown previously by research on tree rings and sediment cores, but is linked to many historical events around the world, from the collapse of the northern WEI dynasty in China to the decline of the city of Teotihuacan, Central America. The Justinian plague that affected the Eastern Roman Empire after the collapse of the Western Roman Empire in 476 may also have been caused in part by cold weather.
Christopher Spencer Queen’s University in Kingston, Canada and his colleagues decided to explore Iceland’s west coast beaches, as they showed it was a light colour, rather than the basalt black of almost every other beach in Iceland.
Its bright colour turned out to be due to the presence of many shells, but while walking through the area, Spencer spotted a cobblestone-sized granite stone. It was immediately clear to him that these rocks were not from Iceland. “It’s a bit embarrassing how easy it is to make a discovery,” he says.
Sure enough, analysis of the rocks confirmed that they came from various parts of Greenland. Greenland is the closest point, about 300 km from Iceland. So, Spencer must have been carried by icebergs spotted and washed away on the beach from Greenland’s glacier.
The beach formations where Greenland rocks reside were previously dated from AD 500 to AD 700, says Spencer. Greenland icebergs can still reach this area, but Greenland Rock has not been found in other layers of the beach.
An ancient rock collection analyzed in the study was traced to Greenland
Dr. Christopher Spencer
Therefore, this finding indicates that numerous Greenlandic Icebergs were washed away at this beach during the period when this layer was formed. This suggests that because of the cold conditions, Greenland’s glaciers grew larger during this period, hiding more icebergs, says Spencer.
This is neatly linked to evidence of cold seasons, sometimes known as the late antique red ice age. The cause of this event is unknown. Some people think it was caused by volcanoes, while others think it was caused by a surprising piece of Earth from a comet. Spencer believes that the solar heat is simply dependent on changes in the orbit that reaches Earth.
The extent to which climate contributed to events such as the collapse of Rome remains debated, but there is growing evidence that climate change has shaped the fate of many civilizations.
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Source: www.newscientist.com