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Volcanic eruptions may explain Denmark’s giant mystery crystals

Volcanic eruptions may explain Denmark's giant mystery crystals
Photo of the Danish Island Fur and it’s sediment layers. Credit: Nicolas Thibault

Some of the world’s largest specimens of rare calcium carbonate crystals, known as glendonites, are found in Denmark.

The crystals were formed between 56 and 54 million years ago, during a period that is known to have had some of the highest temperatures in Earth’s geologic history. Their presence has long stirred wonder among researchers the world over.

“Why we find glendonites from a hot period, when temperatures averaged above 35 degrees, has long been a mystery. It shouldn’t be possible,” explains Nicolas Thibault, an associate professor at the University of Copenhagen’s Department of Geosciences and Natural Resource Management.

This is because glendonites are composed of ikaite, a mineral that is only stable, and can therefore only crystallize, at temperatures of less than four degrees Celsius.

Volcanoes responsible for cold intervals

In their new study, Nicolas Thibault, along with department colleagues Madeleine Vickers, Christian Bjerrum and Christoph Korte, performed chemical analyses of the Danish glendonites.

Their work reveals that the early Eocene Epoch, between 56 and 48 million years ago, was not at all as uniformly warm as once thought.

“Our study proves that there must have been periods of cold during the Eocene Epoch. Otherwise, these crystals couldn’t exist—they would have simply melted. We also propose a suggestion for how this cooling might have happened, and in doing so, potentially solve the mystery of how glendonites in Denmark and the rest of the world came to be,” says Nicolas Thibault. He adds:

“There were probably a large number of volcanic eruptions in Greenland, Iceland and Ireland during this period. These released sulphuric acid droplets into the stratosphere, which could have remained there for years, shading the planet from the sun and reflecting sunlight away. This helps to explain how regionally cold areas were possible, which is what affected the climate in early Eocene Denmark.”

Layers of volcanic ash in rock

The presence of volcanic activity is revealed by, among other things, sedimentary layers visible on Fur, where layers of volcanic ash are clearly visible as bands in the coastal bluffs.

“Our study helps solve a mystery about glendonites, as well as demonstrating that cooler episodes are possible during otherwise warmer climates. The same can be said for today, as we wise up to the possibility of abrupt climate change,” concludes Nicolas Thibault.

Throwing a warm sheet over our understanding of ice and climate

More information:
Madeleine L. Vickers et al, Cold spells in the Nordic Seas during the early Eocene Greenhouse, Nature Communications (2020). DOI: 10.1038/s41467-020-18558-7
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Volcanic eruptions may explain Denmark’s giant mystery crystals (2020, October 14)
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Second giant ‘murder hornet’ escapes after it was captured by scientists in Washington State

Another “murder” hornet that could have led scientists to its nest has evaded experts once more, following a lost signal.

a hand holding a fork and knife: A live Asian giant hornet is affixed with a tracking device using dental floss on October 7 before being released in a photo provided by the Washington State Department of Agriculture.

© Karla Salp/Washington State Department of Agriculture via AP
A live Asian giant hornet is affixed with a tracking device using dental floss on October 7 before being released in a photo provided by the Washington State Department of Agriculture.

Last week, scientists with the Washington State Department of Agriculture (WSDA)captured a live Asian giant hornet — known as “murder” hornets for their ability to decimate honeybee populations — and used dental floss to attach a tracking device to its body, which “worked quite well,” said Sven Spichiger, WSDA’s managing entomologist, during a news conference on Monday.

When scientists released the hornet into the wild onto an apple tree, they were initially successful in tracking the insect, but after some time they were unable to locate a signal when it flew into a heavily vegetated area and then quickly darted away — thus evading the scientists.

Not all hope is lost, though, said Spichiger.

“We did get an initial direction of the flight,” he said. “We were able to meet with several of the property owners and get a few more eyewitness accounts of seeing hornets earlier the week before or earlier in the summer, and so we are starting to narrow down exactly where the hornets’ nest is.”

This isn’t the first time the state has tracked a live giant hornet. The team did so earlier this year, but the tracker fell off the hornet due to gluing issues.

So far, Spichiger said there are at least two Asian giant hornet nests in Whatcom County in Washington, with a possibility of a third.

Once a nest is located, the plan is to vacuum out the hornets and use carbon dioxide gas to knock out any remaining hornets in the nest, he said.

Asian giant hornets are the world’s largest hornet, as they can become up to 2 inches long, according to the WSDA. What makes them so dangerous is that they can destroy a honeybee hive in a matter of hours, killing the bees by decapitating them.

If the hornet becomes established in the state, it will negatively impact the environment, economy and public health, the WSDA said.

Since the preliminary reports in 2019, there have been 18 confirmed Asian giant hornets found in Washington, but there have been even more additional sightings.

a close up of a plant: The captured Asian giant hornet on the apple tree.

© Karla Salp/Washington State Department of Agriculture via AP
The captured Asian giant hornet on the apple tree.

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Giant electrochemical actuation in a nanoporous silicon-polypyrrole hybrid material

Giant electrochemical actuation in a nanoporous silicon-polypyrrole hybrid material
Synthesis of a nanoporous PPy-silicon material. (A) High-angle annular dark-field scanning TEM top view on a nanoporous silicon membrane filled by electropolymerization with pyrrole. The green and red color codes indicate the N and Si concentration resulting from EDX detection measurements, respectively. (B) Voltage-time recording during galvanostatic electropolymerization of pyrrole in nanoporous silicon, with mean pore diameter d and thickness t. Characteristic regimes are indicated and discussed in the main text. Credit: Science Advances, doi: 10.1126/sciadv.aba1483

The absence of piezoelectricity in silicon can lead to direct electromechanical applications of the mainstream semiconductor material. The integrated electrical control of silicon mechanics can open new perspectives for on-chip actuators. In a new report, Manuel Brinker and a research team in physics, materials, microscopy and hybrid nanostructures in Germany, combined wafer-scale nanoporosity in single-crystalline silicon to synthesize a composite demonstrating macroscopic electrostrain in aqueous electrolytes. The voltage-strain coupling was three-orders of magnitude larger than the best performing ceramics. Brinker et al. traced the electro-actuation to the concerted action of a 100 billion nanopores-per-square-centimeter cross-section and obtained exceptionally small operation voltages (0.4 to 0.9 volts) alongside sustainable and biocompatible base materials for biohybrid materials with promising bioactuator applications. The work is now published on Science Advances.

Developing polymers with embedded electrochemical actuation

Electrochemical changes that occur during the oxidation of the conductive polymer polypyrrole (PPy) can increase or decrease the number of delocalized changes in the polymer backbone. When immersed in an electrolyte, the material is accompanied with reversible counter-ion uptake or expulsion with macroscopic contraction as well as swelling under electrical potential control to make PPy one of the most common materials to develop artificial muscle materials. In this work, Brinker et al. combined the actuator polymer with a three-dimensional (3-D) scaffold structure of nanoporous silicon to design a material for embedded electrochemical actuation. The new construct contained a few light and abundant elemental constituents including hydrogen (H), carbon (C), nitrogen (N), oxygen (O), silicon (Si) and chlorine (Cl).

During the experiment, the team prepared the porous silicon (pSi) membrane using an electrochemical etching process of doped silicon in hydrofluoric acid. The resulting pores were straight and perpendicular on the silicon surface. Using scanning electron microscopy profiles, Brinker et al. observed a homogenous sample thickness. They then filled the porous silicon (pSi) membrane with polypyrrole (PPy) through electropolymerization of pyrrole monomers. Polymer nucleation and partial oxidation of pSi increased the open circuit potential leading to a constant deposition of PPy inside the pores. The highly asymmetrical pores formed a chain-like polymer growth inhibiting the branching of the polymer and leading to lower electrical resistance. The team observed the resulting composite using transmission electron micrographs (TEM) with energy-dispersive X-ray (EDX) spectroscopy signals to indicate homogeneous PPy filling of the random pSi honeycomb structure.

Giant electrochemical actuation in a nanoporous silicon-polypyrrole hybrid material
Structural characterization by sorption isotherm, illustration of the polymerization cell and illustration of the electroactuation setup. (A) Nitrogen sorption isotherm at T = 77 K recorded for nanoporous silicon. Plotted is the volume filling fraction f against the relative vapour