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Monday, September 19, 2022

The Brunswick Magnetic Anomaly

 


The Brunswick Magnetic Anomaly is a belt of volcanic rocks that formed around 200 million years ago at the time when the Atlantic Ocean took shape. The ribbon of rock is buried about 9 to 12 miles below the surface. It snakes from Alabama across Georgia, and offshore to North Carolina's Outer Banks.

It is believed that the Brunswick Magnetic Anomaly was created when the crusts of Africa and North America were yanked apart. As North America broke from Pangaea, deep troughs formed along the line of separation. These troughs filled with thick layers of coarse red sandstones, conglomerates, shales, and other nonmarine sediments. Similar sediment-filled troughs (called "rift valleys") occurred along North America’s east coast, from Georgia to Nova Scotia, Canada.

Though North America's east coast is relatively quiet now, clues to these ancient tectonic collisions remain buried deep underground. Using special instruments, geophysicists can discover important information about the large-scale motion of Earth’s outermost shell by determining the source of distinct striped magnetic anomalies.

The Brunswick Magnetic Anomaly may mark the original collision zone between the African and North American plates. At least part of this belt of volcanic rock may represent a suture between the plates east of Georgia. 



Friday, September 2, 2022

Counting and Measuring Tree Rings

 


Dendrochronology is the science of dating events such as volcanic eruptions, forest fires, and environmental changes by studying the characteristic patterns of annual growth rings in timber and tree trunks. Tree cell anatomy contributes to a better understanding of past climate events.

Irina Panyushkina pioneered one of the earliest wood anatomy studies in 1998.She spent the late ’90s in Krasnoyarsk at the Russian Academy of Sciences hunched over a microscope, peering down at paper-thin slices of wood from Arctic larch trees.

Panyushkina painstakingly counted and measured thousands of wood cells to create a 350-year climate chronology, dating from 1642 to 1993. It was among the most rigorous tree-ring–based reconstructions of past climate at the time, but it was also prohibitively tedious. To image the cells, each thin section first had to be photographed under a microscope, and then the images were imported into a computer and displayed onscreen. Panyushkina then had to click on every cell to tell the program to measure it.

Panyushkina took 9,460 photographs from 1,896 tree rings, in just 11 tree samples. The work took her four years. “It was so intensive and laborious,” says Panyushkina, who’s now at the Laboratory of Tree-Ring Research at the University of Arizona. “I said I’ll never do it again.

Fortunately, since Panyushkina's research there have been significant advances in dendrochronology and paleoclimate research because of analytical software and computing power. What would have taken weeks in the ’90s now takes days, says Jesper Björklund at the Swiss Federal Research Institute in Birmensdorf. “Using the same amount of time you can obtain roughly 100 times more data, increasing the potential for robustness and scope of each study,” he says. 

The “big jump,” Björklund says, was the development of a software called ROXAS in the early 2000s, which identifies and measures cells from high-resolution scans of tree rings.

Read more here.

Related reading: Tree Story by Valerie Trouet, Johns Hopkins University, 2020