Powerful volcanic eruption wiped out the Minoan civilization

Hyperaxion Apr 3, 2020

The date of the eruption of the Thera volcano on the Greek island of Santorini, one of the most powerful ever recorded on Earth, has been debated for decades. A new study sheds light on this event that annihilated the ancient Minoan civilization.

Charlotte Pearson, assistant professor of Dendrochronology and Anthropology at the University of Arizona, and her colleagues used a new hybrid approach to assign dates to a sequence of tree rings, spanning the period during which Thera erupted, allowing them to present new evidence that could support an eruption date around 1560 BC.

Powerful volcanic eruption wiped out the Minoan civilization
A new study sheds light on the event that annihilated the ancient Minoan civilization. (Credit: enriquelopezgarrePixabay).

Trees can reveal the past

The trees grow according to the conditions of the local environment. Every year, trees produce a new concentric growth layer, called a ring, which can record information about solar activity, rain, temperature, forest fires or soil conditions.

When a sequence of tree rings of various ages overlap and add up, they can span hundreds or thousands of years, providing information about past weather conditions and the context of competing civilizations.

Tree rings can reveal details about past conditions.
Tree rings can reveal details about past conditions. (Credit: wal_172619Pixabay).

“The longest chronology in the world goes back 12 thousand years. But, in the Mediterranean, the problem is that we haven’t had a complete and continuous record since the time of Thera”, laments Pearson, in a statement. “We have recorded the last 2,000 years very well, but then there’s a gap. We have tree rings from earlier periods, but we don’t know exactly which dates the rings correspond to. This is what’s called a floating chronology.”

Filling this gap can help determine the date of Thera’s eruption and design a climate scenario for the various civilizations that arose and fell during the Bronze and Iron ages.

Since the creation of the UArizona Laboratory of Tree-Ring Research in 1937, a variety of tree ring samples from around the world have accumulated under non-ideal conditions. But since 2013, the team led by Peter Brewer has relocated, organized and preserved samples for future investigations.

The collection includes wood from the Tomb of Midas, in Gordion (Turkey) a giant grave of a man who may have been Midas’ father or grandfather. From woods like these, Peter Kuniholm built a Mediterranean chronology of tree rings of almost half a century.

 Tsunami waves caused by Thera's eruption would have hit directly the Nile delta region
Tsunami waves caused by Thera’s eruption would have hit directly the Nile delta region, having travelled c. 730 km. (Credit Wikimedia Commons).

Despite the length of that chronology, the eruption remained undated and the team decided to try something new. When cosmic rays from space enter the Earth’s atmosphere, neutrons collide with nitrogen atoms to create a radioactive version of carbon, called carbon-14, which spreads across the planet. Tree rings store carbon-14 and have patterns that show how it has changed over time.

Pearson and the team used the carbon-14 patterns of tree rings to anchor the fluctuating chronology to patterns similar to other tree ring sequences dated in the calendar. To validate the findings, the team analyzed the rings of pine (Pinus longaeva) from western North America, which lived at the same time as the trees in Gordion.

 Ruins on Crete, Knossos. Center of Minoan civilization.
Ruins on Crete, Knossos. Center of Minoan civilization. (Credit: Wikimedia Commons).

“When there are major volcanic eruptions, the pine usually heals from freezing during the growing season, creating a ring of frost,” explained Matthew Salzer, a scientist at the Laboratory of Tree-Ring Research.

The method worked. “It showed that wide rings in the Mediterranean chronology occurred in the same years as the frost on the pine. We took this as confirmation that the dating was probably correct”.

The team also used a new technology in the laboratory called “X-ray fluorescence machine” to look for chemical changes in the wood. Something changed the chemistry of the environment in which the tree grew. The acid deposition of a volcano is one possibility, fire is another, but as the date coincides with other ring markers from a major eruption, Pearson said it is worth exploring further.

Although it is a slight fluctuation, it is significant and occurs only at one point in the years around 1560 B.C.

The new study was published in March in the scientific journal Proceedings of the National Academy of Sciences.

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