Ash in Africa
Lane and her colleagues examined ash from Toba recovered from mud extracted from two sites at the bottom of Lake Malawi, the second largest lake in the East African Rift Valley.
"We first started looking for the Toba ash a few years back, but it's a bit like looking for a needle in a haystack, so it took a while," Lane told OurAmazingPlanet. "Between myself and my co-author Ben Chorn, we systematically processed every centimeter of sediment between 24 to 46 meters [78 to 150 feet] depth in the central basin core. The layer is so small that if we leave any gaps in our search, we could miss it completely."
Their analysis discovered that a thin layer of ash in this sediment about 90 feet (27 m) below the lake floor was from the last of the Toba eruptions, known as Youngest Toba Tuff.
"The Toba super-eruption dispersed huge volumes of ash across much of the Indian Ocean, Indian Peninsula and South China Sea," Lane said. "We have discovered the layer of volcanic ash was carried about twice the distance as previously thought, over more than 7,000 kilometers [4,350 miles]."
The amount of ash found in the Malawi sediment core (a cylindrical log of sediment drilled from the ground), was more than the scientists expected to find.
"I was surprised to find so much ash in the Lake Malawi record," Lane added. "The ash is very tiny, composed of shards of volcanic glass smaller than the diameter of a human hair. Nevertheless, in a lot of records I have worked on previously, even within just a few hundreds of miles of an eruption center, we sometimes only find less than 100 shards of glass within a gram of sediment. In Malawi, we have thousands of shards of glass per gram, which really shows how voluminous the Youngest Toba Tuff was."
Ash in Africa
Lane and her colleagues examined ash from Toba recovered from mud extracted from two sites at the bottom of Lake Malawi, the second largest lake in the East African Rift Valley.
"We first started looking for the Toba ash a few years back, but it's a bit like looking for a needle in a haystack, so it took a while," Lane told OurAmazingPlanet. "Between myself and my co-author Ben Chorn, we systematically processed every centimeter of sediment between 24 to 46 meters [78 to 150 feet] depth in the central basin core. The layer is so small that if we leave any gaps in our search, we could miss it completely."
Their analysis discovered that a thin layer of ash in this sediment about 90 feet (27 m) below the lake floor was from the last of the Toba eruptions, known as Youngest Toba Tuff.
"The Toba super-eruption dispersed huge volumes of ash across much of the Indian Ocean, Indian Peninsula and South China Sea," Lane said. "We have discovered the layer of volcanic ash was carried about twice the distance as previously thought, over more than 7,000 kilometers [4,350 miles]."
The amount of ash found in the Malawi sediment core (a cylindrical log of sediment drilled from the ground), was more than the scientists expected to find.
"I was surprised to find so much ash in the Lake Malawi record," Lane added. "The ash is very tiny, composed of shards of volcanic glass smaller than the diameter of a human hair. Nevertheless, in a lot of records I have worked on previously, even within just a few hundreds of miles of an eruption center, we sometimes only find less than 100 shards of glass within a gram of sediment. In Malawi, we have thousands of shards of glass per gram, which really shows how voluminous the Youngest Toba Tuff was."
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