Giant Blobs of Rock, Deep Inside the Earth, Hold Important Clues About Our Planet

Two massive blob-like structures lie deep within Earth, roughly on opposite sides of the planet. The two structures, each the size of a continent and 100 times taller than Mount Everest, sit on the core, 1,800 miles deep, and about halfway to the center of Earth.

Arizona State University scientists Edward Garnero, Allen McNamara and Sang-Heon (Dan) Shim, of the School of Earth and Space Exploration, suggest these blobs are made of something different from the rest of Earth's mantle. The scientists' work appears in the June issue of Nature Geoscience.

"While the origin and composition of the blobs are yet unknown," said Garnero, "we suspect they hold important clues as to how Earth was formed and how it works today."

The blobs, he says, may also help explain the plumbing that leads to some massive volcanic eruptions, as well as the mechanism of plate tectonics from the convection, or stirring, of the mantle. This is the geo-force that drives earthquakes.

Deep stirring

Earth is layered like an onion, with a thin outer crust, a thick viscous mantle, a fluid outer core and a solid inner core. The two blobs sit in the mantle on top of Earth's core, under the Pacific Ocean on one side and beneath Africa and the Atlantic Ocean on the other.

Waves from earthquakes passing through Earth's deep interior have revealed that these blobs are regions where seismic waves travel slowly. The mantle materials that surround these regions are thought to be composed of cooler rocks, associated with the downward movement of tectonic plates.

The blobs, also called thermochemical piles, have long been depicted as warmer-than-average mantle materials, pushed upward by a slow churning of hot mantle rock. The new paper argues they are also chemically different from the surrounding mantle rock, and may partly contain material pushed down by plate tectonics. They might even be material left over from Earth's formation, 4.5 billion years ago.

Much is yet to be learned about these blobs. But the emerging view from seismic and geodynamic information is that they appear denser than the surrounding mantle materials, are dynamically stable and long-lived, and have been shaped by the mantle's large-scale flow. The scientists expect that further work on the two deep-seated anomalies will help clarify the picture and tell of their origin.

"If a neuroscientist found an unknown structure in the human brain, the whole community of brain scientists, from psychologists to surgeons, would actively pursue understanding its role in the function of the whole system," Garnero said.

"As the thermochemical piles come into sharper focus, we hope other Earth scientists will explore how these features fit into the big puzzle of planet Earth."

---

Story Source:

The above post is reprinted from materials provided by Arizona State University (ASU). Note: Materials may be edited for content and length.

Penguin colonies at risk from erupting volcano

A volcano erupting on a small island in the Sub Antarctic is depositing ash over one of the world's largest penguin colonies.

Zavodovski Island is a small island in the South Sandwich archipelago and its volcano Mt Curry has been erupting since March 2016. The island is home to over one million chinstrap penguins -- the largest colony for this species in the world.

The island is part of the British Overseas Territory of South Georgia & the South Sandwich Islands and uninhabited. British Antarctic Survey (BAS) recently remapped this chain of volcanic islands and was alerted to a large (7.2) magnitude earthquake last month in the vicinity.

Researchers confirmed from satellite imagery that not one, but two volcanoes are erupting in the South Sandwich Islands. Mt Curry on Zavodovski Island to the north of the archipelago and Mt Sourabaya on Bristol Island to the south.

Following the earthquake, fishing vessels in the area licenced by the Government of South Georgia & the South Sandwich Islands, captured photos of the Zavodovski Island eruption. They show the main volcanic vent is on the western side of the island, but the prevailing wind is blowing the smoke and ash to the east, and depositing much of it on the lower slopes of the volcano. These are home to the chinstraps, closely packed in great numbers. In addition there are around 180,000 macaroni penguins.

Satellite images have confirmed that between one third and one half of the island has so far been covered in ash. At the time photos were taken, the adult chinstraps were moulting, shedding their old feathers for new ones and therefore unable to leave the island.

Geographer Dr Peter Fretwell from BAS who was involved in the remapping of the archipelago says:

"We don't know what impact the ash will have on the penguins. If it has been heavy and widespread it may have a serious effect on the population. It's impossible to say but two scientific expeditions are scheduled to visit the region from later this year and will try to assess the impact of the eruption."

Penguin ecologist Mike Dunn from BAS says, "As the images were captured during the moult period for the chinstraps, the consequences could be very significant. When the penguins return to breed later in the year, it will be interesting to see what impact this event has on their numbers."

---

Story Source:

The above post is reprinted from materials provided by British Antarctic Survey. Note: Materials may be edited for content and length.

North American forests unlikely to save us from climate change

Forests take up 25 -- 30 percent of human-caused emissions of carbon dioxide -- a strong greenhouse gas -- and are therefore considered to play a crucial role in mitigating the speed and magnitude of climate change. However, a new study that combines future climate model projections, historic tree-ring records across the entire continent of North America, and how the growth rates of trees may respond to a higher concentration of carbon dioxide in the atmosphere has shown that the mitigation effect of forests will likely be much smaller in the future than previously suggested.

Published in the journal Ecology Letters, the study is the first to reveal the possible impact of a changing climate on the growth rate of trees across all of North America, in other words, how their growth changes over time and in response to shifting environmental conditions. The result are detailed forecast maps for the entire North American continent that reveal how forest growth will be impacted by climate change.

The research team, led by scientists at the University of Arizona in Tucson, combined climate projections for North America developed by the International Panel for Climate Change (IPCC) with historic tree-ring records based on samples covering the period 1900 to 1950 at 1,457 sampling sites across the continent.

"We then looked at how the growth of those trees changed historically under various past climates and used that to predict how they will grow in the future across the continent all the way from Mexico to Alaska," said the study's first author, Noah Charney, a postdoctoral research associate in UA's Department of Ecology and Evolutionary Biology.

"The research is unprecedented and novel in the use of big biological data," said co-author Brian Enquist, a professor in the UA's Department of Ecology and Evolutionary Biology and a fellow of the Aspen Center for Environmental Studies in Aspen, Colorado. "We utilized a network of more than two million tree-ring observations spanning North America. Tree-rings provide a record into how trees that grow in different climates respond to changes in temperature and rainfall."

The study calls into question previous conclusions about how forests will respond to warmer average temperatures, increased greenhouse gas emissions, and shifting rainfall patterns.

The team was startled to find no evidence for a greenhouse-gas absorbing process called the boreal greening effect in their simulations. Boreal greening refers to the assumption that trees in high latitudes, where colder temperatures limit growth, should benefit from warmer temperatures and higher concentrations of carbon dioxide in the atmosphere and, as a result, "green" under the effects of climate change. In turn, these thriving boreal forests should be able to scrub more carbon dioxide from the atmosphere, so goes the idea, dampening climate change.

"Until now, there wasn't a good way to take into account how trees respond to climate change under novel climate conditions," added senior author Margaret Evans, an assistant research professor in the UA's Laboratory of Tree-Ring Research (LTRR) and the UA's Department of Ecology and Evolutionary Biology. "Our study provides that perspective. We see that as trees are pushed under the effect of climate change, their response changes."

"Many previous climate modeling studies counted on the boreal forests to save us from the climatic disaster by offsetting our emissions, but we don't' see any greening in our results," said Valerie Trouet, an associate professor in the LTRR. "Instead, we see browning. The positive influence warmer temperatures are believed to have on boreal forests -- we don't see that at all."

The most dramatic changes in projected forest growth rates were found in the interior West of the North American continent, with up to 75 percent slower growth projected for trees in the southwestern U.S., along the Rockies, through interior Canada and Alaska. Increases in growth were seen only along certain coastal areas, mostly in the Pacific Northwest, Northeastern Quebec and the Maritime Provinces and the Florida panhandle.

Some of the predictions arising from the simulations are already happening, the team found.

"In Alaska, for example, where trees have been projected to respond positively to warming temperatures under the boreal greening effect, we see that trees are now responding negatively instead," Evans said. "Trees in very high latitudes are limited by cold temperatures, so yes, in warmer years they grow more, but there is a tipping point, and once they go past that, a warmer climate becomes a bad thing instead of a good thing."

The research indicates that the warming climate already is rapidly pushing many forests towards that tipping point, which may be reached as early as 2050: In addition to being rapidly exposed to temperatures they have not experienced in their lifetimes and are not evolutionarily prepared for, being hampered in their growth makes trees even more vulnerable to added stresses.

"There is a critical and potentially detrimental feedback loop going on here," Charney said. "When the growth rate of trees slows down in response to environmental stressors such as cold or drought, they can get by for a few years, but over time, they deplete their resources and are much more susceptible to additional stressors, such as damage by fire or a big drought or insect outbreaks. Year after year of slow growth therefore means forests become less and less resilient."

As a result, a forest can go from being a climate asset to a carbon producer very quickly.

"It's like a thermostat gone bad," Evans said. "Forests act as a carbon sink by taking carbon dioxide out of atmosphere, but the more the climate is warming, the slower the trees are growing, the less carbon they suck up, the faster the climate is changing."

"The results also highlight the potential importance of locally adapted forest management strategies to help mitigate the decreases in forest growth predicted by our analyses," Charney said.

The implications could potentially apply worldwide. While their models did not include data from outside the North American continent, it "seems very likely that the conclusions drawn in this study apply in the Eurasian forest as well," Evans said. "The boreal forests in Eurasia are more extensive and even more important than the ones in continental North America."

---

Story Source:

The above post is reprinted from materials provided by University of Arizona. Note: Materials may be edited for content and length.

Ancient rocks reveal how Earth recovered from mass extinction

Scientists have shed light on why life on Earth took millions of years to recover from the greatest mass extinction of all time.

The study provides fresh insight into how Earth's oceans became starved of oxygen in the wake of the event 252 million years ago, delaying the recovery of life by five million years.

Findings from the study are helping scientists to better understand how environmental change can have disastrous consequences for life on Earth.

The Permian-Triassic Boundary extinction wiped out more than 90 per cent of marine life and around two thirds of animals living on land. During the recovery period, Earth's oceans became starved of oxygen -- conditions known as anoxia.

Previous research suggested the mass extinction and delayed recovery were linked to the presence of anoxic waters that also contained high levels of harmful compounds known as sulphides.

However, researchers say anoxic conditions at the time were more complex, and that this toxic, sulphide-rich state was not present throughout all the world's oceans.

The team, led by researchers at the University of Edinburgh, used precise chemical techniques to analyse rocks unearthed in Oman that were formed in an ancient ocean around the time of the extinction.

Data from six sampling sites, spanning shallow regions to the deeper ocean, reveal that while the water was lacking in oxygen, toxic sulphide was not present. Instead, the waters were rich in iron.

The finding suggests that iron-rich, low oxygen waters were a major cause of the delayed recovery of marine life following the mass extinction.

The study also shows how oxygen levels varied at different depths in the ocean. While low oxygen levels were present at some depths and restricted the recovery of marine life, shallower waters contained oxygen for short periods, briefly supporting diverse forms of life.

The precise cause of the long recovery period remains unclear, but increased run-off from erosion of rocks on land -- caused by high global temperatures -- likely triggered anoxic conditions in the oceans, researchers say.

The study, published in the journal Nature Communications, was funded by the Natural Environment Research Council and the International Centre for Carbonate Reservoirs. The work is a contribution to the UNESCO International Geoscience Programme. It was carried out in collaboration with the Universities of Leeds, Gratz, Bremen and Vienna University.

Dr Matthew Clarkson, of the University of Edinburgh's School of GeoSciences, who led the study, said: "We knew that lack of oxygen in the oceans played a key role in the extinction and recovery processes, but we are still discovering how exactly it was involved. Our findings about the chemistry of the ocean at the time provide us with a clearer picture of how this complex process delayed the recovery of life for so long."

Professor Simon Poulton, of the University of Leeds, who co-authored the study, said: "The neat point about this study is that it shows just how critical an absence of oxygen, rather than the presence of toxic sulphide, was to the survival of animal life. We found that marine organisms were able to rapidly recolonise areas where oxygen became available."

---

Story Source:

The above post is reprinted from materials provided by University of Edinburgh. Note: Materials may be edited for content and length.

Super-eruptions may give a year's warning before they blow

Super-eruptions -- volcanic events large enough to devastate the entire planet -- give only about a year's warning before they blow.

That is the conclusion of a new microscopic analysis of quartz crystals in pumice taken from the Bishop Tuff in eastern California, which is the site of the super-eruption that formed the Long Valley Caldera 760,000 years ago.

The study is described in the paper "The year leading to a supereruption" by Guilherme Gualda, associate professor of earth and environment sciences at Vanderbilt University, and Stephen Sutton at the University of Chicago published July 20 in the journal PLOS One.

"The evolution of a giant, super-eruption-feeding magma body is characterized by events taking place at a variety of time scales," said Gualda. Tens of thousands of years are needed to prime the crust to generate sufficient eruptible magma. Once established, these melt-rich, giant magma bodies are unstable features that last for only centuries to few millennia. "Now we have shown that the onset of the process of decompression, which releases the gas bubbles that power the eruption, starts less than a year before eruption."

Gualda and Sutton analyzed dozens of small quartz crystals from the Bishop Tuff. Previous investigations of quartz crystals from several super-eruptions, including Long Valley, have noted that they have distinctive surface rims. These studies concluded that the rims formed in less than a century before eruption.

The new study uses a more accurate method for measuring rim growth times pinned on variations in the concentration of titanium in the crystal. Titanium is one of the few impurities that is incorporated into quartz in appreciable amounts and it diffuses fast enough to permit probing of time scales as short as minutes. However, it is extremely difficult to measure the small levels of titanium involved at sufficient spatial resolution. So the researchers established that the concentration of titanium in quartz directly correlates with the amount of light produced when a material is bombarded by electrons, an effect called cathodoluminescence. This allowed them to use cathodoluminescence images to make high-resolution measurements of variations in titanium concentration and, based on this, to determine rim growth times and growth rates.

"Maximum rim growth times span from approximately 1 minute to 35 years, with a median of approximately 4 days. More than 70 percent of rim growth times are less than 1 year, showing that quartz rims have mostly grown in the days to months prior to eruption... . Growth took place under conditions of high supersaturation suggesting that rim growth marks the onset of decompression and the transition from pre-eruptive to syn-eruptive conditions," the paper summarized.

According to Gualda, the decompression period would likely be accompanied by the expansion of the magma body which should have detectable effects on the Earth's surface. While more work is needed to understand what exactly the signs at the surface would be, the study suggests that signs of an impending super-eruption would start to be felt within a year of eruption, and they would intensify as the eruption neared.

Very large eruptions -- including super-eruptions -- have taken place in a number of places worldwide in the recent geological past. The Taupo Volcanic Zone in New Zealand was the site of the most recent super-eruption -- the Oruanui eruption at 26,500 years -- and it includes deposits from more than a dozen very large eruptions that took place in the last couple of million years. Campi Flegrei in Italy produced a very large eruption 40,000 years ago. Indonesia was the site of the Toba super-eruption in Sumatra 75,000 years ago and the Tambora eruption in 1815. In the United States, Yellowstone has experienced three super-eruptions over the last two million years. In light of this evidence, it seems inevitable that another super-eruption will strike the Earth in the future.

"As far as we can determine, none of these places currently house the type of melt-rich, giant magma body needed to produce a super-eruption," said Gualda. "However, they are places where super-eruptions have happened in the past so are more likely to happen in the future."

Gualda and Sutton's study provides new insights into the timescales over which the initiation of such a potentially civilization-ending event would take place.

---

Story Source:

The above post is reprinted from materials provided by Vanderbilt University. The original item was written by David F Salisbury. Note: Materials may be edited for content and length.

2016 climate trends continue to break records

Two key climate change indicators -- global surface temperatures and Arctic sea ice extent -- have broken numerous records through the first half of 2016, according to NASA analyses of ground-based observations and satellite data.

Each of the first six months of 2016 set a record as the warmest respective month globally in the modern temperature record, which dates to 1880, according to scientists at NASA's Goddard Institute for Space Studies (GISS) in New York. The six-month period from January to June was also the planet's warmest half-year on record, with an average temperature 1.3 degrees Celsius (2.4 degrees Fahrenheit) warmer than the late nineteenth century.

Five of the first six months of 2016 also set records for the smallest respective monthly Arctic sea ice extent since consistent satellite records began in 1979, according to analyses developed by scientists at NASA's Goddard Space Flight Center, in Greenbelt, Maryland. The one exception, March, recorded the second smallest extent for that month.

While these two key climate indicators have broken records in 2016, NASA scientists said it is more significant that global temperature and Arctic sea ice are continuing their decades-long trends of change. Both trends are ultimately driven by rising concentrations of heat-trapping carbon dioxide and other greenhouse gases in the atmosphere.

The extent of Arctic sea ice at the peak of the summer melt season now typically covers 40 percent less area than it did in the late 1970s and early 1980s. Arctic sea ice extent in September, the seasonal low point in the annual cycle, has been declining at a rate of 13.4 percent per decade.

"While the El Niño event in the tropical Pacific this winter gave a boost to global temperatures from October onwards, it is the underlying trend which is producing these record numbers," GISS Director Gavin Schmidt said.

Previous El Niño events have driven temperatures to what were then record levels, such as in 1998. But in 2016, even as the effects of the recent El Niño taper off, global temperatures have risen well beyond those of 18 years ago because of the overall warming that has taken place in that time.

The global trend in rising temperatures is outpaced by the regional warming in the Arctic, said Walt Meier, a sea ice scientist at NASA Goddard.

"It has been a record year so far for global temperatures, but the record high temperatures in the Arctic over the past six months have been even more extreme," Meier said. "This warmth as well as unusual weather patterns have led to the record low sea ice extents so far this year."

NASA tracks temperature and sea ice as part of its effort to understand the Earth as a system and to understand how Earth is changing. In addition to maintaining 19 Earth-observing space missions, NASA also sends researchers around the globe to investigate different facets of the planet at closer range. Right now, NASA researchers are working across the Arctic to better understand both the processes driving increased sea ice melt and the impacts of rising temperatures on Arctic ecosystems.

NASA's long-running Operation IceBridge campaign last week began a series of airborne measurements of melt ponds on the surface of the Arctic sea ice cap. Melt ponds are shallow pools of water that form as ice melts. Their darker surface can absorb more sunlight and accelerate the melting process. IceBridge is flying out of Barrow, Alaska, during sea ice melt season to capture melt pond observations at a scale never before achieved. Recent studies have found that the formation of melt ponds early in the summer is a good predictor of the yearly minimum sea ice extent in September.

"No one has ever, from a remote sensing standpoint, mapped the large-scale depth of melt ponds on sea ice," said Nathan Kurtz, IceBridge's project scientist and a sea ice researcher at NASA Goddard. "The information we'll collect is going to show how much water is retained in melt ponds and what kind of topography is needed on the sea ice to constrain them, which will help improve melt pond models."

Operation IceBridge is a NASA airborne mission that has been flying multiple campaigns at both poles each year since 2009, with a goal of maintaining critical continuity of observations of sea ice and the ice sheets of Greenland and Antarctica.

At the same time, NASA researchers began in earnest this year a nearly decade-long, multi-faceted field study of Arctic ecosystems in Alaska and Canada. The Arctic-Boreal Vulnerability Experiment (ABoVE) will study how forests, permafrost and other ecosystems are responding to rising temperatures in the Arctic, where climate change is unfolding faster than anywhere else on the planet.

ABoVE consists of dozens individual experiments that over years will study the region's changing forests, the cycle of carbon movement between the atmosphere and land, thawing permafrost, the relationship between fire and climate change, and more.

---

Story Source:

The above post is reprinted from materials provided by NASA/Goddard Space Flight Center. Note: Materials may be edited for content and length.

Birds on top of the world, with nowhere to go

Climate change could make much of the Arctic unsuitable for millions of migratory birds that travel north to breed each year, according to a new international study published today in Global Change Biology.

The University of Queensland School of Biological Sciences' researcher Hannah Wauchope said that suitable breeding conditions for Arctic shorebirds could collapse by 2070.

"This means that countries throughout the world will have fewer migratory birds reaching their shores," Ms Wauchope said.

Arctic breeding shorebirds undertake some of the longest known migratory journeys in the animal kingdom, with many travelling more than 20,000 kilometres per year to escape the northern winter.

The bar-tailed godwit flies from Alaska to New Zealand in a single flight of 12,000 kilometres without landing.

The study predicts that, in a warming world, migratory birds will become increasingly restricted to small islands in the Arctic Ocean as they retreat north.

This could cause declines in hard-hit regions and some birds could even completely change migratory pathways to migrate closer to suitable habitat.

"Climate change is also opening up the Arctic to threats such as mining and tourism, and we must make sure we protect key places for all Arctic species, including these amazing migratory birds," Ms Wauchope said.

UQ's Associate Professor Richard Fuller from the ARC Centre of Excellence for Environmental Decisions (CEED) said most migratory populations followed well-defined migratory routes.

"This makes shorebirds an excellent group to investigate how climate change might impact breeding grounds and conservation actions that could address these impacts," Associate Professor Fuller said.

The research modelled the suitable climate breeding conditions of 24 Arctic shorebirds and projected them to 2070.

The researchers also examined the impact on Arctic birds of the world's last major warming event about 6000 to 8000 years ago.

"Climatically suitable breeding conditions could shift and contract over the next 70 years, with up to 83 per cent of Arctic bird species losing most of their currently suitable area," Ms Wauchope said.

"This far exceeds the effects of the last major warming event on Earth, but genetic evidence suggests that even then the birds struggled to deal with the warming."

She said that suitable climatic conditions are predicted to decline fastest in the areas with most species (western Alaska and eastern Russia), where Arctic birds are already becoming vulnerable to the "shrubification" of the tundra, and predators such as red foxes moving north.

---

Story Source:

The above post is reprinted from materials provided by University of Queensland. Note: Materials may be edited for content and length.