Once land becomes established through dynamic processes like plate tectonics, it begins to weather and add crucial minerals and nutrients to the ocean. A record of these nutrients is preserved in the ancient rock record. Previous research used strontium isotopes in marine carbonates, but these rocks are usually scarce or altered in rocks older than 3 billion years.

Now, researchers are presenting a new approach to trace the first emergence of old rocks using a different mineral: “barite.”

Barite forms from a combination of sulfate coming from ocean water mixing with barium from hydrothermal vents. Barite holds a robust record of ocean chemistry within its structure, useful for reconstructing ancient environments. “The composition of the piece of barite we pick up in the field now that has been on Earth for three and a half billion years, is exactly the same as it was when it when it actually precipitated,” says Desiree Roerdink, a geochemist at University of Bergen, Norway, and team leader of the new research. “So in essence, it is really a great recorder to look at processes on the early Earth.”

Roerdink and her team tested six different deposits on three different continents, ranging from about 3.2 billion to 3.5 billion years old. They calculated the ratio of strontium isotopes in the barite, and from there, inferred the time where the weathered continental rock made its way to the ocean and incorporated itself into the barite. Based on the data captured in the barite, they found that weathering started about 3.7 billion years ago — about 500 million years earlier than previously thought.

“That is a huge time period,” Roerdink says. “It essentially has implications for the way that we think about how life evolved.” She added that scientists usually think about life starting in deep sea, hydrothermal settings, but the biosphere is complex. “We don’t really know if it is possible that life could have developed at the same time on land,” she noted, adding “but then that land has to be there.”

Lastly, the emergence of land says something about plate tectonics and the early emergence of a geodynamic Earth. “To get land, you need processes operating to form that continental crust, and form a crust that is chemically different from the oceanic crust,” Roerdink says.

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The locations of the North and South poles aren’t static, unchanging spots on our planet. The axis Earth spins around — or more specifically the surface that invisible line emerges from — is always moving due to processes scientists don’t completely understand. The way water is distributed on Earth’s surface is one factor that drives the drift.

Melting glaciers redistributed enough water to cause the direction of polar wander to turn and accelerate eastward during the mid-1990s, according to a new study in Geophysical Research Letters, AGU’s journal for high-impact, short-format reports with immediate implications spanning all Earth and space sciences.

“The faster ice melting under global warming was the most likely cause of the directional change of the polar drift in the 1990s,” said Shanshan Deng, a researcher at the Institute of Geographic Sciences and Natural Resources Research at the Chinese Academy of Sciences, the University of the Chinese Academy of Sciences and an author of the new study.

The Earth spins around an axis kind of like a top, explains Vincent Humphrey, a climate scientist at the University of Zurich who was not involved in this research. If the weight of a top is moved around, the spinning top would start to lean and wobble as its rotational axis changes. The same thing happens to the Earth as weight is shifted from one area to the other.

Researchers have been able to determine the causes of polar drifts starting from 2002 based on data from the Gravity Recovery and Climate Experiment (GRACE), a joint mission by NASA and the German Aerospace Center, launched with twin satellites that year and a follow up mission in 2018. The mission gathered information on how mass is distributed around the planet by measuring uneven changes in gravity at different points.

Previous studies released on the GRACE mission data revealed some of the reasons for later changes in direction. For example, research has determined more recent movements of the North Pole away from Canada and toward Russia to be caused by factors like molten iron in the Earth’s outer core. Other shifts were caused in part by what’s called the terrestrial water storage change, the process by which all the water on land — including frozen water in glaciers and groundwater stored under our continents — is being lost through melting and groundwater pumping.

The authors of the new study believed that this water loss on land contributed to the shifts in the polar drift in the past two decades by changing the way mass is distributed around the world. In particular, they wanted to see if it could also explain changes that occurred in the mid-1990s.

In 1995, the direction of polar drift shifted from southward to eastward. The average speed of drift from 1995 to 2020 also increased about 17 times from the average speed recorded from 1981 to 1995.

Now researchers have found a way to wind modern pole tracking analysis backward in time to learn why this drift occurred. The new research calculates the total land water loss in the 1990s before the GRACE mission started.

“The findings offer a clue for studying past climate-driven polar motion,” said Suxia Liu, a hydrologist at the Institute of Geographic Sciences and Natural Resources Research at the Chinese Academy of Sciences, the University of the Chinese Academy of Sciences and the corresponding author of the new study. “The goal of this project, funded by the Ministry of Science and Technology of China is to explore the relationship between the water and polar motion.”

Water loss and polar drift

Using data on glacier loss and estimations of ground water pumping, Liu and her colleagues calculated how the water stored on land changed. They found that the contributions of water loss from the polar regions is the main driver of polar drift, with contributions from water loss in nonpolar regions. Together, all this water loss explained the eastward change in polar drift.

“I think it brings an interesting piece of evidence to this question,” said Humphrey. “It tells you how strong this mass change is — it’s so big that it can change the axis of the Earth.”

Humphrey said the change to the Earth’s axis isn’t large enough that it would affect daily life. It could change the length of day we experience, but only by milliseconds.

The faster ice melting couldn’t entirely explain the shift, Deng said. While they didn’t analyze this specifically, she speculated that the slight gap might be due to activities involving land water storage in non-polar regions, such as unsustainable groundwater pumping for agriculture.

Humphrey said this evidence reveals how much direct human activity can have an impact on changes to the mass of water on land. Their analysis revealed large changes in water mass in areas like California, northern Texas, the region around Beijing and northern India, for example — all areas that have been pumping large amounts of groundwater for agricultural use.

“The ground water contribution is also an important one,” Humphrey said. “Here you have a local water management problem that is picked up by this type of analysis.”

Liu said the research has larger implications for our understanding of land water storage earlier in the 20th century. Researchers have 176 years of data on polar drift. By using some of the methods highlighted by her and her colleagues, it could be possible to use those changes in direction and speed to estimate how much land water was lost in past years.

Debora Rodrigues, Ezekiel Cullen Professor of Engineering at the University of Houston Cullen College of Engineering, in collaboration with Francisco C. Robles Hernandez, professor at the UH College of Technology and Ellen Aquino Perpetuo, professor at the University of Sao Paulo, Brazil offered conclusive research for understanding how bacteria found in copper mines convert toxic copper ions to stable single-atom copper.

In their co-authored paper, “Copper Mining Bacteria: Converting toxic copper ions into a stable single atom copper,” their research demonstrates how copper-resistant bacterium from a copper mine in Brazil convert copper sulfate ions into zero-valent metallic copper.

“The idea of having bacteria in mines is not new, but the unanswered question was: what are they doing in the mines?” Robles said. “By putting the bacteria inside an electronic microscope, we were able to figure out the physics and analyze it. We found out the bacteria were isolating single atom copper. In terms of chemistry, this is extremely difficult to derive. Typically, harsh chemicals are used in order to produce single atoms of any element. This bacterium is creating it naturally that is very impressive.”

As useful as copper is, the process of mining the metal often leads to toxic exposures and challenges on drawing out substantial volume for commercial use. Approximately one billion tons of copper are estimated in global reserves, according to the Copper Development Association Inc., with roughly 12.5 million metric tons per year mined. This aggregates to roughly 65 years of remaining reserves. Part of the supply challenge comes from limited available copper in high concentration in the earth’s crust, but the other challenge is the exposure to sulfur dioxide and nitrogen dioxide in the copper smelting and production process to concentrate the metal into useful quantities.

“The novelty of this discovery is that microbes in the environment can easily transform copper sulfate into zero valent single atom copper. This is a breakthrough because the current synthetic process of single atom zerovalent copper is typically not clean, it is labor intensive and expensive,” Rodrigues said.

“The microbes utilize a unique biological pathway with an array of proteins that can extract copper and convert it into single-atom zero-valent copper. The aim of the microbes is to create a less toxic environment for themselves by converting the ionic copper into single-atom copper, but at the same time they make something that is beneficial for us too.”

With a focus in electronic microscopy, Robles examined samples from Rodrigues’ findings in Brazilian copper mines and he determined the single atom nature of the copper. Rodrigues and Aquino’s groups further identified the bacterial process for converting copper sulfate to elemental copper — a rare find.

Research results demonstrate this new conversion process as an alternative to produce single atoms of metallic coper is safer, and more efficient versus current methods (i.e. chemical vapor deposition, sputtering and femtosecond laser ablation).

“We have only worked with one bacterium, but that may not be the only one out there that performs a similar function,” Rodrigues concluded. “The next step for this particular research is harvesting the copper from these cells and using it for practical applications.”

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Materials provided by University of Houston. Note: Content may be edited for style and length.