Turkey’s Volcanic Landscape: A Journey Through Time

Despite being far from tectonic plate borders, scientists have long wondered how volcanoes in central Anatolia formed. Now, they have discovered evidence of a hot plume of magma flowing from East Africa.

Turkey is situated in one of the world’s seismically active zones, encircled by three larger plates and sitting atop the Anatolian tectonic plate. The magnitude 7. 8 and 7. In February 2023, the Anatolian plate collided with the Arabian plate to the south, resulting in five massive earthquakes that devastated Syria and Turkey. Scientists have long been perplexed by one feature of this part of the world, though: why do the volcanoes in Turkey’s interior lie so far away from tectonic boundaries, which are typically hotspots for volcanic activity?

Scientists believe they have found a solution in an investigation that was documented in the journal Geochemistry, Geophysics, Geosystems. By analyzing underground seismic waves and surface rock markers, they discovered evidence of a horizontally flowing molten rock channel beneath the Anatolian plate. This magma in the Earth’s upper mantle sticks close to the surface and feeds volcanism because it is hotter and moving more quickly than the surrounding material.

This magma flow originates from the East African Rift, a system of crustal fissures located over 1,250 miles away, which the team also located. The research indicates that the horizontal magma channel, which feeds volcanoes along its route and hardly cools as it descends underground, is propelled by a plume of molten rock rising within the rift, where the African plate is splitting apart.

A geophysicist at the GFZ German Research Center for Geosciences in Potsdam, Fergus McNab, says that although he was not involved in the study, observations around the Icelandic plume, for example, support the idea that plume material can move quickly and over great distances along the base of the tectonic plate. But these are longer distances, and it is unusual that volcanism is still happening at these kinds of distances. ”.

Horizontal plume travel has been modeled elsewhere, including beneath Hawaii and parts of the Pacific Ocean. Together, these findings suggest that mantle material can travel far farther without losing much heat than previously thought, which may help to explain some volcanic activity that happens in unexpected places.

Turkey has long been plagued by volcanoes; the most recent eruption occurred on July 2, 1840, when heat from the magma caused water inside Mount Ararat to erupt. The blast triggered a landslide that swept over nearby villages, killing around 1,900 people.

The eruption has long puzzled scientists, since Mount Ararat is several hundred miles from a tectonic boundary. Most of Earth’s volcanoes are clustered around hotspots, which are large, fractured rock slabs at the edge of the tectonic plates that float slowly atop the planet’s mantle like gigantic egg shells. When these plates collide, one normally sinks below the other, releasing molten rock that drives volcanoes above.

But there are several volcanic fields that lie in the middle of tectonic plates. These so-called intraplate volcanoes are occasionally fed by hot rock plumes that rise vertically from the mantle. On the other hand, some take place in locations where no such plume is visible, like beneath Mount Ararat in Anatolia.

Some scientists have theorized that the activity is caused by local tectonic processes, such as the lower plate collapsing into the mantle, based on previous research on the volcanism surrounding the Anatolia plate. But these explanations alone don’t quite match up with the high temperatures seen spread throughout the region. So Junlin Hua, a geologist at the University of Texas at Austin, and colleagues dug a little deeper.

Utilizing both seismic and geochemical hints, the researchers examined the temperature and mantle profile beneath eastern Anatolia. Seismic imaging in the asthenosphere, a region of the planet’s interior, revealed a channel that is 60–90 feet deep. This channel slows down waves, suggesting higher temperatures and partially molten mantle.

The team then analyzed data from 117 basalt samples found in Turkey’s Karacadağ volcanic field. Erupted magma crystallizes in a specific way that can reveal details of its formation. They estimated the temperature in the channel to be about 2,600 degrees Fahrenheit, which is 95 degrees hotter than the surrounding mantle, based on these data.

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Subsequently, the scientists investigated chemical isotopes in basalt samples that were gathered from various locations along the 1,250-mile channel that links Turkey and East Africa. Using information from 1,004 rock samples, they found overlapping traces of strontium, neodymium, and lead isotopes, suggesting a shared origin.

“The magmas are telling us theyre consistent,” says Karen Fischer, a seismologist at Brown University and co-author on the study. “Theyre also telling us that theyre consistent with the same source in the mantle.”

These rocks’ subsequent modeling showed that the magma in the channel moves fast enough to maintain a temperature higher than that of the asthenosphere around it. The models indicate that in order to maintain this heat, the magma is moving at a rate of about 24 centimeters per year, and it will take nearly 11 million years for it to reach Anatolia. This may seem slow, but for magma working its way through the dense mantle, it’s quite fast.

“These flows can be among the fastest mantle movements on Earth,” says Maxim Ballmer, a geodynamicist at University College London who wasn’t involved in the study.

The authors propose that this speed is driven by the pressure from the upwelling plume of the East African Rift and the reduced viscosity of the hotter magma. “Whats really important is that it’s still hot, so it can generate these volcanoes,” Hua says.

How exactly the channel started remains an open question that could be explored in future work. “It is not thoroughly investigated, but one possibility. is that plate spreading in the Red Sea encouraged northward flow,” McNab states.

A clue was found in the isotopes: a shift in composition that occurred roughly 10 million years ago, in tandem with the Anatolian and Arabian plates colliding. According to Hua, this suggests that the channel—which may have already extended as far as Jordan—may have found a new opening during the tectonic collision.

Otherworldly plumes

The new research is forcing scientists to reevaluate how far material from a rising plume can travel before causing a volcanic eruption. “Material from mantle plumes can reach and alter parts of the Earth far more quickly than one may think,” says Fischer. “It appears that there are corridors thousands of kilometers away where plumes can genuinely impact the upper mantle. ” ”.

It was previously thought that plumes would radiate as a disk when they reached the surface, but this research has shown that they can now disperse quickly and widely across thin channels. “If you picture a plume shooting out tendrils in a variety of directions, this phenomenon can start to make sense,” says Fischer.

This could account for part of the mysterious volcanic activity observed in the past, such as in the Central Atlantic magmatic province, an area of widespread volcanism that happened concurrently with Pangea’s breakup approximately 200 million years ago. The runaway volcanic activity is thought to have caused a mass extinction at the end of the Triassic.

The work could also inform future volcanism research on other planets, like Venus, which has no plate tectonics but does appear to have plume-like activity. And studying the churnings of our planet’s interior and the movements of its tectonic plates can help us understand the environments that form on the surface.

Ballmer notes that the understanding of how earthquake and volcanic eruption processes also contribute to stabilizing ocean volume and climate over millions or billions of years is relatively new. This understanding is crucial for the maintenance of surface conditions over long enough timescales to support the evolution of higher life forms. ”.

The Active Volcano in Turkey; Mount Ararat

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