Guest Post: Unusual volcanism in the central Andes

Today we have another guest post on Eruptions, this time by Morgan Salisbury, a Ph.D. candidate at Oregon State University. He will be taking you to look at some of the volcanism in the Central Andes of South America. Enjoy!


Unusual volcanism in the central Andes – Morgan J. Salisbury

The central Andes of South America is an exciting place to study volcanology. The continental crust in the here is thicker than almost anywhere else on earth and certainly the thickest with abundant volcanism. The vast Altiplano-Puna plateau that comprises the central Andes is second in height and width only to the Tibetan Plateau, the latter of which formed by the collision of two continental plates. In contrast, the Altiplano-Puna plateau was constructed at the boundary of the oceanic Nazca plate and the continental South American Plate, an arrangement that generally does not produce thickened crust and large plateaus. Because of crystallization and assimilation with the thick, low-density crust of the Altiplano-Puna, mantle-derived magmas are inevitably significantly altered the time they erupt on the surface of the plateau. The contamination makes it very difficult to determine why the mantle melted in the first place, particularly in the eastern regions of the plateau, well behind the more obviously subduction-related volcanoes of the arc front. Unaltered lavas that all volcanologists to determine the mechanisms of mantle melting are virtually non-existent in the Altiplano-Puna. But this is why I think studying these volcanoes is so interesting, we are trying to figure out the root cause of their existence, which remains a matter of debate. It’s a relief to know that such simple questions remain unanswered in this day and age.

Location map of Altiplano-Puna plateau of the central Andes. Volcán Tunupa is a composite cone located east of the arc front near the center of the Altiplano basin in Bolivia. Click here to see larger version.

Subduction zone volcanism has persisted along the western edge of South America for at least 200 million years but only since about 25 million years ago did volcanoes start appearing in abundance east of the arc front in what is now the interior of Bolivia. The shift from focused to widespread volcanism is undoubtedly related to growth of the Altiplano-Puna plateau, but the exact process remains unknown. One of the more interesting hypotheses is that the behind arc (east of the arc front) volcanism is due to lithospheric detachment, often referred to as delamination, or foundering. In this scenario, crust and the underlying lithospheric mantle that has been pushed deep into the earth by the mountain building process becomes denser than the asthenospheric mantle, detaches, and then sinks. Magma can then be generated by decompression melting as the asthenosphere ascends to fill in the space of the detached lithosphere. Although there is supporting evidence for lithospheric detachment form geophysical data, the process remains unproven. Alternatively, arc volcanism may either be particularly diffuse in this region, or complex asthenospheric convection may be responsible for the widespread volcanism in the continental interior.

Volcán Tunupa from the north. The town of Salinas de García Mendoza is in the foreground. Click here to see a larger version.

I think that volcanology has a lot to the debate, with the first step being to obtain radiometric ages and chemical composition for lavas from the behind arc volcanoes. Knowing the timing, location, and geochemistry of volcanism will help reveal the process that resulted in the likely related processes of mantle melting and plateau formation. As part of my PhD at Oregon State University I looked into the chronology and chemistry of lavas that constructed the behind arc Tunupa volcano, which is located on the Bolivian Altiplano between the giant salt flats known as the Salar de Uyuni and the Salar de Coipasa. With help from my collaborators, I found that the volcano was constructed about 1.5 million years ago, younger than previous age determinations had suggested. The lavas also have unusual chemistry that differs from the volcanoes of the arc front. Although it is difficult to tell exactly what caused the mantle to melt beneath Volcán Tunupa, the results from the study do seem to point to complicated processes that could fall in line with the lithospheric detachment hypothesis. There are other possibilities of course, but it is a very exciting time to work in this region. There are many volcanoes left to explore and many problems that remain to be solved.

View from Tunupa looking south towards the Salar de Uyuni and snow-capped volcanoes in the background. Click here to see a larger version.

Top left: Another view of Tunupa in Bolivia

Big Think Edge
  • The meaning of the word 'confidence' seems obvious. But it's not the same as self-esteem.
  • Confidence isn't just a feeling on your inside. It comes from taking action in the world.
  • Join Big Think Edge today and learn how to achieve more confidence when and where it really matters.

To boost your self-esteem, write about chapters of your life

If you're lacking confidence and feel like you could benefit from an ego boost, try writing your life story.

Personal Growth

In truth, so much of what happens to us in life is random – we are pawns at the mercy of Lady Luck. To take ownership of our experiences and exert a feeling of control over our future, we tell stories about ourselves that weave meaning and continuity into our personal identity.

Keep reading Show less

Yale scientists restore brain function to 32 clinically dead pigs

Researchers hope the technology will further our understanding of the brain, but lawmakers may not be ready for the ethical challenges.

Still from John Stephenson's 1999 rendition of Animal Farm.
Surprising Science
  • Researchers at the Yale School of Medicine successfully restored some functions to pig brains that had been dead for hours.
  • They hope the technology will advance our understanding of the brain, potentially developing new treatments for debilitating diseases and disorders.
  • The research raises many ethical questions and puts to the test our current understanding of death.

The image of an undead brain coming back to live again is the stuff of science fiction. Not just any science fiction, specifically B-grade sci fi. What instantly springs to mind is the black-and-white horrors of films like Fiend Without a Face. Bad acting. Plastic monstrosities. Visible strings. And a spinal cord that, for some reason, is also a tentacle?

But like any good science fiction, it's only a matter of time before some manner of it seeps into our reality. This week's Nature published the findings of researchers who managed to restore function to pigs' brains that were clinically dead. At least, what we once thought of as dead.

What's dead may never die, it seems

The researchers did not hail from House Greyjoy — "What is dead may never die" — but came largely from the Yale School of Medicine. They connected 32 pig brains to a system called BrainEx. BrainEx is an artificial perfusion system — that is, a system that takes over the functions normally regulated by the organ. The pigs had been killed four hours earlier at a U.S. Department of Agriculture slaughterhouse; their brains completely removed from the skulls.

BrainEx pumped an experiment solution into the brain that essentially mimic blood flow. It brought oxygen and nutrients to the tissues, giving brain cells the resources to begin many normal functions. The cells began consuming and metabolizing sugars. The brains' immune systems kicked in. Neuron samples could carry an electrical signal. Some brain cells even responded to drugs.

The researchers have managed to keep some brains alive for up to 36 hours, and currently do not know if BrainEx can have sustained the brains longer. "It is conceivable we are just preventing the inevitable, and the brain won't be able to recover," said Nenad Sestan, Yale neuroscientist and the lead researcher.

As a control, other brains received either a fake solution or no solution at all. None revived brain activity and deteriorated as normal.

The researchers hope the technology can enhance our ability to study the brain and its cellular functions. One of the main avenues of such studies would be brain disorders and diseases. This could point the way to developing new of treatments for the likes of brain injuries, Alzheimer's, Huntington's, and neurodegenerative conditions.

"This is an extraordinary and very promising breakthrough for neuroscience. It immediately offers a much better model for studying the human brain, which is extraordinarily important, given the vast amount of human suffering from diseases of the mind [and] brain," Nita Farahany, the bioethicists at the Duke University School of Law who wrote the study's commentary, told National Geographic.

An ethical gray matter

Before anyone gets an Island of Dr. Moreau vibe, it's worth noting that the brains did not approach neural activity anywhere near consciousness.

The BrainEx solution contained chemicals that prevented neurons from firing. To be extra cautious, the researchers also monitored the brains for any such activity and were prepared to administer an anesthetic should they have seen signs of consciousness.

Even so, the research signals a massive debate to come regarding medical ethics and our definition of death.

Most countries define death, clinically speaking, as the irreversible loss of brain or circulatory function. This definition was already at odds with some folk- and value-centric understandings, but where do we go if it becomes possible to reverse clinical death with artificial perfusion?

"This is wild," Jonathan Moreno, a bioethicist at the University of Pennsylvania, told the New York Times. "If ever there was an issue that merited big public deliberation on the ethics of science and medicine, this is one."

One possible consequence involves organ donations. Some European countries require emergency responders to use a process that preserves organs when they cannot resuscitate a person. They continue to pump blood throughout the body, but use a "thoracic aortic occlusion balloon" to prevent that blood from reaching the brain.

The system is already controversial because it raises concerns about what caused the patient's death. But what happens when brain death becomes readily reversible? Stuart Younger, a bioethicist at Case Western Reserve University, told Nature that if BrainEx were to become widely available, it could shrink the pool of eligible donors.

"There's a potential conflict here between the interests of potential donors — who might not even be donors — and people who are waiting for organs," he said.

It will be a while before such experiments go anywhere near human subjects. A more immediate ethical question relates to how such experiments harm animal subjects.

Ethical review boards evaluate research protocols and can reject any that causes undue pain, suffering, or distress. Since dead animals feel no pain, suffer no trauma, they are typically approved as subjects. But how do such boards make a judgement regarding the suffering of a "cellularly active" brain? The distress of a partially alive brain?

The dilemma is unprecedented.

Setting new boundaries

Another science fiction story that comes to mind when discussing this story is, of course, Frankenstein. As Farahany told National Geographic: "It is definitely has [sic] a good science-fiction element to it, and it is restoring cellular function where we previously thought impossible. But to have Frankenstein, you need some degree of consciousness, some 'there' there. [The researchers] did not recover any form of consciousness in this study, and it is still unclear if we ever could. But we are one step closer to that possibility."

She's right. The researchers undertook their research for the betterment of humanity, and we may one day reap some unimaginable medical benefits from it. The ethical questions, however, remain as unsettling as the stories they remind us of.

Ashes of cat named Pikachu to be launched into space

A space memorial company plans to launch the ashes of "Pikachu," a well-loved Tabby, into space.

GoFundMe/Steve Munt
Culture & Religion
  • Steve Munt, Pikachu's owner, created a GoFundMe page to raise money for the mission.
  • If all goes according to plan, Pikachu will be the second cat to enter space, the first being a French feline named Felicette.
  • It might seem frivolous, but the cat-lovers commenting on Munt's GoFundMe page would likely disagree.
Keep reading Show less