A study from Carnegie Mellon University tracks the travels of tarantulas since the Cretaceous period.
- Scary-looking tarantulas actually prefer to keep to themselves and stay in their burrows.
- Their sedentary nature makes a puzzle of their presence in so many places around the world.
- Researchers discover that this is because they've been around a very long time and rode drifting continental land masses to their contemporary positions.
Whenever a movie script calls for the protagonist to be menaced by a spider, central casting typically places a call to a tarantula wrangler. Tarantulas, or theraphosids, are hairy and big — they're the largest spiders in the world — and for many people, the ultimate spider nightmare.
Reality is much tamer. Tarantulas are not actually aggressive. They're homebodies, preferring to spend their time in their burrows with their families. Females and their young hardly ever leave home, and males only go out to mate. Stay away from them, and they'll stay away from you.
This makes tarantulas' presence on six out of seven continents something of a mystery. How did such non-adventurous creatures end up in so many places? A new study published in the journal PeerJ from a team of international researchers provides the answer: They walked there as they rafted across the earth atop drifting continental masses.
Ancestry.com for tarantulas
Credit: Foley, et al./ PeerJ
The lead author of the study is Carnegie Mellon University's Saoirse Foley, whose team included researchers from Universität Trier in Germany and Yale-NUS College in Singapore. Together, they conducted a wide-ranging analysis of 48 spider transcriptomes, a compilation of RNA transcripts inside of cells. The researchers used the transcriptomes to construct a "family tree."
The tarantula family tree was then time-calibrated using fossil data. (Tarantula fossils are rare, so the team used software to assist in the calculation using the ages of fossils from other types of spiders.)
Combined, the data allowed the researchers to construct a tarantula family tree dating back about 120 million years to the Cretaceous period. Around this time, giant crocodiles were walking — yes walking on legs — in South Korea.
Landmasses on the move
A map of Godwana 240 million years ago.Fama Clamosa/Wikimedia Commons
Tarantulas are Americans from a time when the Americas were part of the supercontinent Gondwana and still attached to Australia, Africa, Antarctica, and India.
The researchers tracked tarantulas' migration atop pieces of Gondwana as the landmasses slowly assumed their current positions.
A few detours along the way
The study identifies tarantulas' ancestral ranges.Credit: Foley, et al. /PeerJ/ Map credit: https://mapchart.net, 2021. Licensed under CC BY 4.0 SA.
The research revealed that tarantula migration wasn't just a matter of riding the continents.
Researchers discovered that the spiders may have done some dispersing through the areas in which they found themselves. Their arrival into Asia was, for example, two-pronged. Once the tarantulas were in India, they split into two groups — one group stayed on the ground while the other took to the trees — before that landmass collided with Asia and the spiders moved northward. The two groups arrived in Asia 20 million years apart from each other.
This is a bit of a surprise says Foley, noting that the two Indian variants demonstrate tarantula adaptability at work:
"Previously, we did not consider tarantulas to be good dispersers. While continental drift certainly played its part in their history, the two Asian colonization events encourage us to reconsider this narrative. The microhabitat differences between those two lineages also suggest that tarantulas are experts at exploiting ecological niches, while simultaneously displaying signs of niche conservation."
A recent study of Iceland's Krafla volcanic caldera suggests hidden magma pools may be lurking under many of the world's volcanic systems.
- The study analyzed magma collected from a 2009 incident in which geothermal drillers encountered magma that geophysical surveys failed to detect.
- Currently, magma imaging technology can't accurately detect magma pools under a certain size.
- Hidden magma pools pose safety concerns because magma from other sources might combine with the hidden magma, which could trigger unexpectedly explosive eruptions.
In 2009, scientists with the Deep Drilling Project were drilling a mile-deep borehole into Iceland's Krafla volcanic caldera when magma suddenly began creeping into the hole. The team had known, based on geophysical surveys, that a large magma body lay about two miles below the surface. But the surveys had failed to warn of molten rock at these shallower depths.
It was a concerning oversight. After all, Krafla is one of the world's most closely monitored volcanic systems, so if volcanologists can't detect shallow magma there, what does that suggest about risk assessments at other volcanoes?
A new study published in Geology explores the potential threats of such hidden magma pools, or "covert silicic magma." The researchers used the 2009 Krafla incident to assess how hidden magma pools form and whether they might pose previously unknown eruptions risks.
The devil's in the magma
To better understand the origins of hidden magma pools, the researchers took magma samples from the 2009 Krafla incident and compared them to seven other recorded eruptions within the Krafla caldera involving rhyolite, a silica-rich type of volcanic rock that's especially explosive.
At first, the team thought the hidden magma pool formed during relatively passive eruptions during the 1980s. But the analysis revealed the samples to be "essentially indistinguishable" from rocks ejected by Krafla's most recent explosive eruption: a mixed hydrothermal-magmatic event that occurred in 1724.
Credit: Rooyakkers et al
Still, the researchers couldn't determine exactly how the magma pool formed or has behaved since then, nor could they determine the size of the pool. That's mostly because modern magma-detecting instruments, such as seismic tomography, can't accurately identify magma pools smaller than about 1 cubic kilometer.
How could these relatively small magma pools pose major threats? One reason centers on composition. For example, the drillers involved in the Krafla incident struck rhyolitic magma, which is more explosive than basalt, the type of magma that dominates the Krafla caldera.
As basalt ascends toward the surface, it could potentially combine with and "mobilize" the rhyolitic magma, causing a violent eruption that offers "little warning," the researchers wrote.
"So the concern in this case would be that you have a shallow rhyolitic magma that you don't know about, so it hasn't been considered in hazards planning," study author Shane Rooyakkers said in a press release published by The Geological Society of America. "If it's hit by new magma moving up, you might have a much more explosive eruption than you were anticipating."
To better understand and forecast such eruptions, the researchers called for improving magma-detection strategies, such as using extremely dense geophone arrays, which use soundwaves to monitor the earth for seismic events.
If magma-detection technology improves, scientists might someday be able to install sensors around previously hidden magma pools, which could provide warnings of upcoming eruptions. But for now, volcanologists still have much to learn about hidden magma pools, and their prevalence around the globe.
Satellite imagery can help better predict volcanic eruptions by monitoring changes in surface temperature near volcanoes.
- A recent study used data collected by NASA satellites to conduct a statistical analysis of surface temperatures near volcanoes that erupted from 2002 to 2019.
- The results showed that surface temperatures near volcanoes gradually increased in the months and years prior to eruptions.
- The method was able to detect potential eruptions that were not anticipated by other volcano monitoring methods, such as eruptions in Japan in 2014 and Chile in 2015.
How can modern technology help warn us of impending volcanic eruptions?
One promising answer may lie in satellite imagery. In a recent study published in Nature Geoscience, researchers used infrared data collected by NASA satellites to study the conditions near volcanoes in the months and years before they erupted.
The results revealed a pattern: Prior to eruptions, an unusually large amount of heat had been escaping through soil near volcanoes. This diffusion of subterranean heat — which is a byproduct of "large-scale thermal unrest" — could potentially represent a warning sign of future eruptions.
Conceptual model of large-scale thermal unrestCredit: Girona et al.
For the study, the researchers conducted a statistical analysis of changes in surface temperature near volcanoes, using data collected over 16.5 years by NASA's Terra and Aqua satellites. The results showed that eruptions tended to occur around the time when surface temperatures near the volcanoes peaked.
Eruptions were preceded by "subtle but significant long-term (years), large-scale (tens of square kilometres) increases in their radiant heat flux (up to ~1 °C in median radiant temperature)," the researchers wrote. After eruptions, surface temperatures reliably decreased, though the cool-down period took longer for bigger eruptions.
"Volcanoes can experience thermal unrest for several years before eruption," the researchers wrote. "This thermal unrest is dominated by a large-scale phenomenon operating over extensive areas of volcanic edifices, can be an early indicator of volcanic reactivation, can increase prior to different types of eruption and can be tracked through a statistical analysis of little-processed (that is, radiance or radiant temperature) satellite-based remote sensing data with high temporal resolution."
Temporal variations of target volcanoesCredit: Girona et al.
Although using satellites to monitor thermal unrest wouldn't enable scientists to make hyper-specific eruption predictions (like predicting the exact day), it could significantly improve prediction efforts. Seismologists and volcanologists currently use a range of techniques to forecast eruptions, including monitoring for gas emissions, ground deformation, and changes to nearby water channels, to name a few.
Still, none of these techniques have proven completely reliable, both because of the science and the practical barriers (e.g. funding) standing in the way of large-scale monitoring. In 2014, for example, Japan's Mount Ontake suddenly erupted, killing 63 people. It was the nation's deadliest eruption in nearly a century.
In the study, the researchers found that surface temperatures near Mount Ontake had been increasing in the two years prior to the eruption. To date, no other monitoring method has detected "well-defined" warning signs for the 2014 disaster, the researchers noted.
The researchers hope satellite-based infrared monitoring techniques, combined with existing methods, can improve prediction efforts for volcanic eruptions. Volcanic eruptions have killed about 2,000 people since 2000.
"Our findings can open new horizons to better constrain magma–hydrothermal interaction processes, especially when integrated with other datasets, allowing us to explore the thermal budget of volcanoes and anticipate eruptions that are very difficult to forecast through other geophysical/geochemical methods."
A new study provides a possible scientific explanation for the existence of stories about ancient saints performing miracles with water.
Ancient and near ancient records are often less than trustworthy. Even if you ignore the parts with reports of sea monsters or ants that mine gold, certain events often seem exaggerated. If we trust what the Greeks wrote, we'd have to assume Persia invaded with an impossibly high percentage of their entire population. The Romans, fond of showing how horrible the people they subdued were, spoke of the Celts using the Wicker Man for human sacrifice, though we can find no hard evidence of Wicker Men having existed.
You can probably understand why most historians take certain claims with a grain of salt, especially when those claims talk about dramatic events.
One seemingly mundane area this includes is the weather. What one person might record as an unprecedented weather event another person might think of as normal. Determining which account is correct a thousand years after the fact can be difficult, assuming that neither of them was exaggerating in the first place.
Luckily, as science marches on, it can provide new ways to investigate the past. An international team of researchers has managed to use isotopes from stalagmites in Northern Italy to better understand what the weather was like in the sixth century and to provide evidence for some fantastic historical records.
Ancient truths hidden in a cave
In a recent study published in Climatic Change, researchers investigated stalagmites in a cave in Tuscany. Stalagmites, which are the pointy rock formations on the ground in caves, provide a record of the environmental conditions they formed in. By examining different parts of the stalagmites, the team could determine what the climate was like, for instance if it was wetter or drier than normal, at different points in history. Uranium-thorium dating was used to provide precise dates for these points.
Oxygen isotope ratios were then measured to distinguish between wetter and drier periods. Combining this with the uranium-thorium data, the researchers could compile a timeline of climate activity over several hundred years. The oxygen isotope ratios in the sixth century indicated unusually wet weather.
The authors speculate that the moisture could have come from the North Atlantic Oscillation's negative phase, which tends to push moist air into Italy.
The water miracles of the Italian saints
Stalagmite Sample RL12, which was the focus of this study. Points on the sample that were used for dating and isotope collection are labeled. Zanchetta et al
While these findings provide strong evidence for lots of rain in Sixth Century Italy, this isn't the first report to suggest that the weather might have been extreme at the time.
Records of the saints from that time feature numerous examples of holy men somehow controlling troublesome water. One, the tale of St. Frigidian, features the saint successfully commanding the Serchio river to flow into a raked track he created, saving Lucca from flooding. A fifth of the miracles described in the Dialogues on the Miracles of the Italian Fathers, a record of saints, are "water miracles" of this kind.
While it is true that some of the most noteworthy miracles in the Bible involve water , such as the parting of the Red Sea by Moses, the miracles described in Dialogues are often unique feats with no obvious literary precursor, suggesting that they aren't repeats of existing stories in a new setting.
Additionally, French religious documents from the same period have no similar emphasis on water miracles. This suggests, though does not prove, that the Italians had separate motivations for listing so many of them.
Does this mean we can start trusting any old document?
Co-author Robert Wiśiewski of the University of Warsaw explained how documents like the Dialogues can be used to help improve our understanding of history:
"Literary sources, in particular stories about saints, should not be taken as a direct record of past events, They do, however, reflect the worldview of church writers and the basis for their interpretation of extraordinary weather phenomena."
A new study makes a compelling case for the origin of unexplained masses of underground rock causing changes to the Earth's magnetic field.
They're called "large low-shear-velocity provinces" (LLSVPs), and they're large anomalous globs of, well, some kind of rock deep inside the Earth. There's one under Africa and the other is beneath the Pacific Ocean. Together, they're apparently producing the South Atlantic Anomaly, a massive region of lower magnetic intensity sufficient to weaken the planet's corresponding magnetic field. This provides less protection from cosmic rays for our orbiting spacecraft, and some wonder whether its presence signals a flipping of the planets magnetic poles. It's believed the anomaly is nothing new, reappearing now and again for at least 11 million years and likely much longer.
A theory from researchers at Arizona State University (ASU) presented this month at the Lunar and Planetary Science Conference may explain what the LLSVPs actually are: They're what's left of the protoplanet Theia that crashed into the young Earth about 4.5 billion years ago, shearing off the debris that eventually became our Moon.
Credit: 3000ad/Adobe Stock
According to a widely held hypothesis, Theia was an at-least Mars-sized object that obliquely collided with Earth. It's a good thing it just glanced off us, too, since a direct hit would have obliterated our planet entirely. As it was, it's theorized, two big chunks were ejected from the collision, forming two moons that eventually coalesced into the one we see today.
The authors of the new research, led by ASU's Qian Yuan, explain in a summary of their findings: "Such a model is well-aligned with some key physical aspects of Earth-Moon system, including anomalous high angular momentum of Earth-Moon system, small iron core of the Moon and its high mass ratio compared to the Earth."
But if Theia was real, where did it go? The authors write, "The Giant Impact hypothesis is one of the most examined models for the formation of the Moon, but direct evidence indicating the existence of the impactor Theia remains elusive." It's reasonable that some material from both bodies was destroy. How much of Theia was captured has remained an open question.
Scientists have conclusively determined that the LLSVPs exist, though their origin and composition is unresolved. The ASU researchers say that while they could be thermal in origin, seismological examination reveals that they have distinct margins separating them from surrounding rock and are much denser chemically, suggesting that they're not of a piece with the rest of the mantle.
The researchers' modeling of Theia's likely composition supports the idea that its mantle was several percent denser than Earth's, and iron-rich, which would mean that after the bodies collided, the Theia mantle material could "sink to Earth's lowermost mantle and accumulate into thermochemical piles that may cause seismically observed LLSVPs."
The theory proposed in the new research, which is being evaluated for publication in the journal Geophysical Research Letters, has been proposed before. However, the ASU researchers have presented what may be the best supporting evidence for it yet. Yuan says his research supports the LLSVP-Theia connection in four ways:
- The LLSVPs' mass may be equivalent to the size of Theia's mantle, answering the question of where it went after impact.
- At a minimum of 250 million years old, the LLSVPs predate the Moon.
- The hypothesized makeup of Theia's mantle matches what is believed to be the composition of the LLSVPs.
- Simulations show how Theia's mantle could end up where the LLSVPs currently are.