A new study from the Desert Research Institute (DRI) found that two separate volcanic eruptions that happened in the 6th century may be the triggering events for the fall of the Roman Empire. The environmental chaos that happened during that time including famines and plagues are close to being deemed as the primary cause of the Great Migration Period in the first millennium.
The researchers tried to clarify the inconsistencies surrounding the contributions of volcanic eruptions to climate variability. In this new study, the scientists show that these volcanic eruptions in the high latitude and tropical areas are the main causes of temperature changes in the Northern Hemisphere in the last 2,500 years.
The study published in the journal Nature studied ice sheets from more than 20 ice cores located in the Antarctic and Greenland, including the thousand-year-old tree rings found in the northern hemisphere.
The researchers found that out of the 16 coolest summers recorded between 500 B.C. and 1,000 A.D., 15 were preceded by massive volcanic eruptions. These high-temperature summers continued for about 15 years; hence, problems in crop production and famine persisted. Along with this environmental chaos is the social turmoil and mass migration that happened during this time, probably leading to the Justinian plague.
According to the scientists, the volcanic sulfate and ash released to the upper atmosphere envelopes the surface of the Earth and inhibited cosmic rays and solar radiation from penetrating through the planet. This is the main reason why the volcanic eruptions that happened during those years led to cool summers and climate changes, and were also subsequently linked to the famines and pandemics at that time.
Marc Caffee, a Physics professor from the Purdue University, who was also part of the study, particularly utilized an electrostatic accelerator to measure the amounts of the radioactive isotope beryllium-10 in each individual ice layers. This isotope is formed when the oxygen in the atmosphere and the cosmic rays interact but decays at a specified rate when enclosed in ice. With this, Caffee and the entire team investigated the remaining amounts of beryllium-10 in the ice cores to identify the estimated period with which it has been trapped inside.
"With new high-resolution records emerging from ice cores in Greenland and Antarctica, it will be possible to extend this reconstruction of volcanic forcing probably all the way back into the last Ice Age," says Michael Sigl, the study's lead author.
Photo: Börkur Sigurbjörnsson | Flickr
