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Amy G. Ryan, James K. Russell, Michael J. Heap, Mark E. Zimmerman, and Fabian B. Wadsworth

Whether volcanoes will erupt explosively depends on the behavior of gases trapped in the subsurface. If gas pressures are high within a volcano, the surrounding magma and rocks can break, causing explosive eruptions. Alternatively, if gases vent to the surface through interconnected void spaces, explosive behavior does not occur. Void spaces in volcanoes are ephemeral – numerous processes can close them. Here we show that solid state sintering – a historically neglected process – operates pervasively and efficiently within volcanic conduits. We use high-temperature-pressure experiments and models to characterize and understand the timescales of this process under typical volcanic conditions. Our resarch shows the timescales (days to weeks) to be commensurate with the periodicity of explosive eruptions during lava dome producing eruptions.

Elise M. Olson, Susan E. Allen, Vy Do, Michael Dunphy, and Debby Ianson

The University of British Columbia sits on a promontory overlooking the Salish Sea. As you look out over the water, you see its quickly changing variations in color and roughness. That is just the surface! We have run a model (SalishSeaCast: salishsea.eos.ubc.ca) every day since 2014 to capture the motion of the water, the mixing, and the changes in temperature and salinity. Now we have added a biological component so we can see changes in the phytoplankton growth as the phytoplankton blooms in the spring, then dies back due to nutrient limitation and grazing by zooplankton. Events, like wind storms, that resupply nutrients to the sunlit surface waters, can trigger new phytoplankton growth during summer months. In the manuscript, we present the model and its evaluation showing how accurately it represents this seasonal cycle and variability in time and space. We show that strong tidal flow through the narrow Discovery Passage, near Campbell River, leads to turbulent mixing, bringing deep nutrients to the surface. Tidal currents carry these nutrient-rich surface waters into the northern Strait of Georgia, relieving nutrient limitation and allowing phytoplankton to grow, contributing to the region's fish and shellfish productivity.

Strong tidal flow through the narrow Discovery Passage, near Campbell River, leads to turbulent mixing, bringing deep nutrients to the surface. Tidal currents carry these nutrient-rich surface waters into the northern Strait of Georgia, relieving nutrient limitation and allowing phytoplankton to grow, contributing to the region's fish and shellfish productivity.

Manar is a research scientist in the Department of Earth, Ocean & Atmospheric Sciences at the University of British Columbia. She is interested in understanding the evolution of different parts of the solar system and its constituents. Her research career started with studying the interactions between Mercury’s magnetic field and the solar wind, and continued through her involvement as a scientific collaborator and Deputy Instrument Scientist on the OSIRIS-REx mission, the first NASA mission to attempt to bring a pristine sample back to Earth from an asteroid. Manar will begin her Ph.D. at the University of Berkley in January 2020 where she will expand her knowledge of planetary evolution through the study of the motion of material throughout Earth. Her main focus will be the interactions between the core and mantle throughout Earth’s history.

Pacific Museum of Earth · Quarantine Conversation with Manar Al Asad - Planetary Scientist

Maya Kopylova, E Tso, F Ma, and D G Pearson

Sifting through diamond exploration samples from Baffin Island, Canadian scientists have identified a new remnant of the North Atlantic craton—an ancient part of Earth's continental crust.

A chance discovery by geologists poring over diamond exploration samples has led to a major scientific payoff.

Kimberlite rock samples are a mainstay of diamond exploration. Formed millions of years ago at depths of 150 to 400 kilometres, kimberlites are brought to the surface by geological and chemical forces. Sometimes, the igneous rocks carry diamonds embedded within them.

"With these samples we’re able to reconstruct the shapes of ancient continents based on deeper, mantle rocks.”

“For researchers, kimberlites are subterranean rockets that pick up passengers on their way to the surface,” explains University of British Columbia geologist Maya Kopylova. “The passengers are solid chunks of wall rocks that carry a wealth of details on conditions far beneath the surface of our planet over time.”

But when Kopylova and colleagues began analyzing samples from a De Beers Chidliak Kimberlite Province property in southern Baffin Island, it became clear the wall rocks were very special. They bore a mineral signature that matched other portions of the North Atlantic craton—an ancient part of Earth's continental crust that stretches from Scotland to Labrador.

“The mineral composition of other portions of the North Atlantic craton is so unique there was no mistaking it,” says Kopylova, lead author of a new paper in the Journal of Petrology that outlines the findings. “It was easy to tie the pieces together. Adjacent ancient cratons in Northern Canada—in Northern Quebec, Northern Ontario and in Nunavut—have completely different mineralogies.”

Cratons are billion-year old, stable fragments of continental crust—continental nuclei that anchor and gather other continental blocks around them. Some of these nuclei are still present at the center of existing continental plates like the North American plate, but other ancient continents have split into smaller fragments and been re-arranged by a long history of plate movements.

“Finding these 'lost' pieces is like finding a missing piece of a puzzle,” says Kopylova. “The scientific puzzle of the ancient Earth can’t be complete without all of the pieces.”

The continental plate of the North Atlantic craton rifted into fragments 150 million years ago, and currently stretches from northern Scotland, through the southern part of Greenland and continues southwest into Labrador.

The newly identified fragment covers the diamond bearing Chidliak kimberlite province in southern Baffin Island. It adds roughly 10 percent to the known expanse of the North Atlantic craton.

This is the first time geologists have been able to piece parts of the puzzle together at such depth—so called mantle correlation. Previous reconstructions of the size and location of Earth’s plates have been based on relatively shallow rock samples in the crust, formed at depths of one to 10 kilometres.

"With these samples we’re able to reconstruct the shapes of ancient continents based on deeper, mantle rocks,” says Kopylova. “We can now understand and map not only the uppermost skinny layer of Earth that makes up one percent of the planet’s volume, but our knowledge is literally and symbolically deeper. We can put together 200-kilometre deep fragments and contrast them based on the details of the deep mineralogy.”

The samples from the Chidliak Kimberlite Province in southern Baffin Island were initially provided by Peregrine Diamonds, a junior exploration company. Peregrine was acquired by the international diamond exploration company and retailer De Beers in 2018. The drill cores sample themselves are very valuable, and expensive to retrieve.

“Our partner companies demonstrate a lot of goodwill by providing research samples to UBC, which enables fundamental research and the training of many grad students,” says Kopylova. “In turn, UBC research provides the company with information about the deep diamondiferous mantle that is central to mapping the part of the craton with the higher changes to support a successful diamond mine.”

Kohen Bauer, Matthijs Smit, Roger Francois, Sean Crowe, and co-authors

Evolution of Earth’s surface chemistry and biology are chronicled by minerals contained in rocks. For example, magnetite, an abundant iron mineral in Precambrian sedimentary iron formations (IFs), records the chemistry and biology of the ancient oceans and atmosphere. Mechanisms of magnetite deposition in IFs are uncertain, and thus so too are records of chemistry and biology in IFs. We find that magnetite forms unusual, raspberry-like, framboidal grains through microbial iron reduction in the waters of ancient ocean analogues, lakes Matano and Towuti (Indonesia). This magnetite is a major source of Fe to the underlying sediment, and the same mechanisms likely contributed to IF deposition. The conspicuous magnetite framboids may provide a biosignature on early Earth, Mars, and other planetary bodies.

Catherine Johnson, Anna Mittelholz and the NASA InSIGHT Science team

Fluctuations in field provide clues about upper atmosphere

New data gleaned from the magnetic sensor aboard NASA’s InSight spacecraft is offering an unprecedented close-up of magnetic fields on Mars.

In a study published today in Nature Geoscience, scientists reveal that the magnetic field at the InSight landing site is ten times stronger than anticipated, and fluctuates over time-scales of seconds to days.

“One of the big unknowns from previous satellite missions was what the magnetization looked like over small areas,” said lead author Catherine Johnson, a professor at the University of British Columbia and senior scientist at the Planetary Science Institute. “By placing the first magnetic sensor at the surface, we have gained valuable new clues about the interior structure and upper atmosphere of Mars that will help us understand how it – and other planets like it – formed.”

Zooming in on magnetic fields

Before the InSight mission, the best estimates of Martian magnetic fields came from satellites orbiting high above the planet, and were averaged over large distances of more than 150 kilometres.

“The ground-level data give us a much more sensitive picture of magnetization over smaller areas, and where it’s coming from,” said Johnson. “In addition to showing that the magnetic field at the landing site was ten times stronger than the satellites anticipated, the data implied it was coming from nearby sources.”

Scientists have known that Mars had an ancient global magnetic field billions of years ago that magnetized rocks on the planet, before mysteriously switching off. Because most rocks at the surface are too young to have been magnetized by this ancient field, the team thinks it must be coming from deeper underground.

“We think it’s coming from much older rocks that are buried anywhere from a couple hundred feet to ten kilometres below ground,” said Johnson. “We wouldn’t have been able to deduce this without the magnetic data and the geology and seismic information InSight has provided.”

The team hopes that by combining these InSight results with satellite magnetic data and future studies of Martian rocks, they can identify exactly which rocks carry the magnetization and how old they are. 

Day-night fluctuations and things that pulse in the dark

The magnetic sensor has also provided new clues about phenomena that occur high in the upper atmosphere and the space environment around Mars.

Just like Earth, Mars is exposed to solar wind, which is a stream of charged particles from the Sun that carries an interplanetary magnetic field (IMF) with it, and can cause disturbances like solar storms. But because Mars lacks a global magnetic field, it is less protected from solar weather.

“Because all of our previous observations of Mars have been from the top of its atmosphere or even higher altitudes, we didn’t know whether disturbances in solar wind would propagate to the surface,” said Johnson. “That’s an important thing to understand for future astronaut missions to Mars.”

The sensor captured fluctuations in the magnetic field between day and night and short, mysterious pulsations around midnight, confirming that events in and above the upper atmosphere can be detected at the surface.

The team believe that the day-night fluctuations arise from a combination of how the solar wind and IMF drape around the planet, and solar radiation charging the upper atmosphere and producing electrical currents, which in turn generate magnetic fields.

“What we’re getting is an indirect picture of the atmospheric properties of Mars – how charged it becomes and what currents are in the upper atmosphere,” said co-author Anna Mittelholz, a postdoctoral fellow at the University of British Columbia.

And the mysterious pulsations that mostly appear at midnight and last only a few minutes?

“We think these pulses are also related to the solar wind interaction with Mars, but we don’t yet know exactly what causes them,” said Johnson. “Whenever you get to make measurements for the first time, you find surprises and this is one of our ‘magnetic’ surprises.”

In the future, the InSight team wants to observe the surface magnetic field at the same time as the MAVEN orbiter passes over InSight, allowing them to compare data. 

“The main function of the magnetic sensor was to weed out magnetic “noise,” both from the environment and the lander itself, for our seismic experiments, so this is all bonus information that directly supports the overarching goals of the mission,” said InSight principal investigator Bruce Banerdt of NASA’s Jet Propulsion Laboratory in Pasadena, California. “The time-varying fields, for example, will be very useful for future studies of the deep conductivity structure of Mars, which is related to its internal temperature.”

The study is one of six new papers published today that chronicle the first year of NASA’s InSight Mission.

Credit: J.T. Keane; Nature Geoscience

Video: Overview of InSight mission goals