- Scientists have discovered proof of a beforehand unknown volcanic eruption within the southern Aegean Sea from 520,000 years in the past.
- Researchers drilled into the seabed, extracting cores with thick pumice layers that point out a volcanic origin. Scientists have named this layer the Archaeos Tuff.
- The largely underwater explosion was huge, about ten occasions bigger than the Hunga Tonga-Hunga Ha’apai volcanic eruption of January 22, 2022.
By Molly Colleen McCanta, University of Tennessee
Beforehand unknown volcanic eruption revealed
“Core on deck!”
For 2 months, every time I heard that cry, I might run as much as the deck of the JOIDES Resolution to observe the crew pull up a 30-foot (10-meter) cylindrical tube stuffed with layered, multicolored rock and sediment drilled from the seafloor beneath our ship.
Within the winter of 2022, I spent two months cruising the south Aegean Sea on board the Worldwide Ocean Discovery Program’s JOIDES Decision as a part of IODP Expedition 398. My geologist colleagues and I used this former oil exploration ship to drill deep into the seafloor and reveal the volcanic historical past of the realm off the coast of Santorini, Greece.
I’m a scientist who research the chemistry of volcanic rocks. I take advantage of my experience to correlate volcanic sediments to the eruption that prompted them and to know the circumstances that magma skilled each at depth beneath a volcano and through an eruption.
Our expedition’s drilling of the seafloor revealed a large however previously unknown volcanic eruption that passed off greater than 500,000 years in the past. This discovery expands our understanding of the volcanic exercise within the chain of volcanoes comprising the South Aegean Volcanic Arc. And it will enable for a extra correct hazard evaluation of this area.
Constructing a extra full volcanic historical past
Archaeologists have lengthy been fascinated with the late Bronze Age eruption of Santorini round 1600 BCE. This eruption is related to the decline of the Minoan civilization on the close by island of Crete. Geologists even have important curiosity within the area, as a result of volatility of the volcanic and seismic exercise on this space. Particularly as a result of the realm is house to about 15,000 residents and attracts round 2 million tourists per yr.
Though there’s important on-land documentation of the Santorini volcano, scientists know this file is incomplete. On land, erosion, vegetation and extra eruptive occasions typically cowl or obscure older volcanic deposits, leading to a fragmentary historical past. The deep-sea drilling enabled by the IODP’s JOIDES Decision provides researchers entry to a geologic file not often preserved on land.
How the ocean preserves a volcanic eruption layer
Following a volcanic eruption, pyroclastic supplies – items of rock and ash fashioned in the course of the eruption – settle by means of the water column to gather on the seafloor. There, clays and organic materials, such because the shells of tiny marine organisms, rain down repeatedly. As they do, they cap the volcanic rock deposits. This course of preserves a file of a person eruption as a single layer. Layers construct with time, with every successive volcanic occasion making a near-continuous chronologic file of the volcanic historical past of the area.
Expedition 398’s mission was to entry this deep-sea file as a way to doc the intensive historical past of eruptions in every space of concentrated volcanic exercise.
IODP Expedition 398
IODP Expedition 398 collected drill cores to higher perceive the volcanic historical past and recurrence interval of the Santorini, Christiana and Kolumbo volcanoes on this area. The JOIDES Decision crew drilled 12 websites to a most depth of two,950 toes (900 meters) beneath the seafloor. We recovered greater than 11,000 toes (3,356 meters) of total core over 780 cores.
As technicians minimize the core into 4 1/2-foot (1 1/2-meter) sections, scientists would collect to see the fabric. After bringing the cores to floor stress, the workforce would cut up them lengthwise, {photograph} them, analyze them for bodily properties akin to magnetic susceptibility and describe the fabric. Core describers measure and file the geologic composition of every rocky unit contained inside.
Because the geochemistry lab lead, I took small samples of a number of layers of volcanic rock and ash to dissolve into resolution and analyze for his or her hint aspect composition. Throughout an eruption, magma crystallizes and mixes with parts within the water and rock it comes into contact with. The ensuing chemical adjustments within the magma are distinctive to the circumstances of that exact eruption. So as soon as I work out the chemical composition of the deposit samples, I can fingerprint their volcanic origin.
Our discovery: The Archaeos Tuff
Through the expedition, our group of researchers found a thick, white pumice layer at a number of websites in a number of totally different basins. Shipboard biostratigraphy dated every incidence of the layer to the identical age: between 510,000 and 530,000 years in the past. Geochemical correlations prompt the composition was the identical throughout drill holes as effectively.
Discovering the identical layer throughout these basins permits our analysis workforce to mannequin how large the accountable eruption might need been. We used seismic knowledge collected in the course of the expedition to find out the majority quantity of the volcanic sediment is about 21 cubic miles (90 cubic kilometers). As well as, it had thicknesses as much as 490 toes (150 meters) in some locations. Plus, we decided this layer of volcanic rock was unfold over 1,100 sq. miles (3,000 sq. kilometers) of this area within the southern Aegean Sea.
Uncovering a big volcanic eruption
Primarily based on the Archaeos Tuff’s traits, we will perceive the character of the volcanic eruption that fashioned it. Its thickness and distribution over a large space counsel the Archaeos Tuff is the results of a single, high-intensity eruption. The quite a few vesicles, or tiny holes, within the rock point out a launch of a considerable amount of gasoline concurrently the liquid magma. These little gasoline bubbles paint an image of a strong eruption through which a substantial amount of risky gasoline was launched fairly shortly.
But regardless of its evident measurement and ferocity, this eruption didn’t correlate with any beforehand identified on-land deposits or massive eruptions. The relative lack of on-land materials suggests a primarily submarine eruption. As soon as we knew what we have been in search of, our workforce was in a position to match our newly found deep-sea layer of volcanic sediment to a couple small, beforehand uncorrelated on-land deposits on Santorini, Christiana and Anafi islands. The presence of those deposits signifies some breach of the ocean floor in the course of the eruption, which once more matches with our image of an lively eruption.
Placing the volcanic eruption measurement into context
Additional examine of the Archaeos Tuff’s composition and age confirmed the distinctive nature of the rock deposit left by this eruption. Primarily based on the information we collected, our workforce believes the Archaeos Tuff is the results of an eruption six occasions larger than the Bronze Age Minoan eruption, abandoning rock deposits 30 occasions thicker. The presence of such a big volcanic deposit tells us that the South Aegean Volcanic Arc is extra able to producing massive submarine volcanic eruptions than scientists beforehand acknowledged.
One other expedition member, Steffen Kutterolf of the GEOMAR Helmholtz Centre for Ocean Analysis in Kiel, told Phys.org:
The newly found tuff deposit has a quantity of greater than 90 cubic kilometers and is as much as 150 meters thick. This makes it ten occasions bigger than the Hunga Tonga-Hunga Ha’apai volcanic eruption of January 22, 2022.
Assessing volcanic hazards of the south Aegean Sea
Figuring out the Archaeos Tuff expands what we learn about volcanic processes within the south Aegean Sea. It suggests a larger propensity for hazardous submarine volcanism than beforehand realized. And officers have to reevaluate volcanic hazards to the encompassing inhabitants.
However researchers agree they don’t count on one other volcanic eruption of this magnitude within the close to future.
Molly Colleen McCanta, Affiliate Professor of Petrology and Planetary Geoscience, University of Tennessee
This text is republished from The Conversation below a Artistic Commons license. Learn the original article.
Backside line: Researchers have discovered proof within the layers of the seafloor of the Aegean Sea for a beforehand unknown huge volcanic eruption some 520,000 years in the past.
