Faculty of Arts & Science; Research; Faculty & Staff

University of Toronto-led research suggests some major changes to geology textbooks

krisha — Fri, 10 Jun 2016 17:31:31 +0000

University of Toronto-led research suggests some major changes to geology textbooks krisha Fri, 06/10/2016 - 13:31

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Moraine Lake at Banff National Park. Photo by Russell Pyslkywec

Peter McMahon

Author legacy

Peter McMahon

Topic

Breaking Research

Faculty of Arts & Science; Research; Faculty & Staff

Subheadline

“A potentially major revision to the fundamental idea of plate tectonics”

Super-computer modelling of the Earth’s crust and upper-mantle suggests that ancient geologic events may have left deep ‘scars’ that can come to life to play a role in earthquakes, mountain formation, and other ongoing processes on our planet.

This changes the widespread view that only interactions at the boundaries between continent-sized tectonic plates could be responsible for such events.

A team of researchers from the University of Toronto and the University of Aberdeen have created models indicating that former plate boundaries may stay hidden deep beneath the Earth’s surface. These multi-million-year-old structures, situated at sites away from existing plate boundaries, may trigger changes in the structure and properties at the surface in the interior regions of continents.

“This is a potentially major revision to the fundamental idea of plate tectonics,” says lead author Philip Heron, a postdoctoral fellow in Russell Pysklywec’s research group in U of T’s department of Earth sciences. Their paper, “Lasting mantle scars lead to perennial plate tectonics,” appears in the June 10, 2016 edition of Nature Communications.

A new map of Earth’s ancient geology

Heron and Pysklywec, together with University of Aberdeen geologist Randell Stephenson have even proposed a ‘perennial plate tectonic map’ of the Earth to help illustrate how ancient processes may have present-day implications.

“It’s based on the familiar global tectonic map that is taught starting in elementary school,” says Pysklywec, who is also chair of U of T’s department of Earth sciences. “What our models redefine and show on the map are dormant, hidden, ancient plate boundaries that could also be enduring or “perennial” sites of past and active plate tectonic activity.”

To demonstrate the dominating effects that anomalies below the Earth’s crust can have on shallow geological features, the researchers used U of T’s SciNet – home to Canada’s most powerful computer and one of the most powerful in the world – to make numerical models of the crust and upper-mantle into which they could introduce these scar-like anomalies.

Fig. 1, below. A proposed perennial plate tectonic map. Present-day plate boundaries (white lines), with hidden ancient plate boundaries that may reactivate to control plate tectonics (yellow lines). Image credit: Russell Pysklywec, Philip Heron, Randell Stephenson.

Simulating yesterday’s continents

The team essentially created an evolving “virtual Earth” to explore how such geodynamic models develop under different conditions.

“For these sorts of simulations, you need to go to a pretty high-resolution to understand what’s going on beneath the surface,” says Heron. “We modeled 1,500 kilometres across and 600 kilometres deep, but some parts of these structures could be just two or three kilometres wide. It is important to accurately resolve the smaller-scale stresses and strains.”

Using these models, the team found that different parts of the mantle below the Earth’s crust may control the folding, breaking, or flowing of the Earth’s crust within plates — in the form of mountain-building and seismic activity – when under compression.

In this way, the mantle structures dominate over shallower structures in the crust that had previously been seen as the main cause of such deformation within plates.

“The mantle is like the thermal engine of the planet and the crust is an eggshell above,” says Pysklywec. “We’re looking at the enigmatic and largely unexplored realm in the Earth where these two regions meet.”

An Earth in hibernation

“Most of the really big plate tectonic activity happens on the plate boundaries, like when India rammed into Asia to create the Himalayas or how the Atlantic opened to split North America from Europe,” says Heron. “But there are lots of things we couldn’t explain, like seismic activity and mountain-building away from plate boundaries in continent interiors.”

The research team believes their simulations show that these mantle anomalies are generated through ancient plate tectonic processes, such as the closing of ancient oceans, and can remain hidden at sites away from normal plate boundaries until reactivation generates tectonic folding, breaking, or flowing in plate interiors.

“Future exploration of what lies in the mantle beneath the crust may lead to further such discoveries on how our planet works, generating a greater understanding of how the past may affect our geologic future,” says Heron.

The research carries on the legacy of J. Tuzo Wilson, also a U of T scientist, and a legendary figure in geosciences who pioneered the idea of plate tectonics in the 1960’s.

“Plate tectonics is really the cornerstone of all geoscience,” says Pysklywec. “Ultimately, this information could even lead to ways to help better predict how and when earthquakes happen. It’s a key building block.”

The transcendent value of disgust: U of T’s Jeannie Miller offers a new perspective on an Arabic scholar

vzaretski — Fri, 29 Apr 2016 15:57:19 +0000

The transcendent value of disgust: U of T’s Jeannie Miller offers a new perspective on an Arabic scholar

vzaretski Fri, 04/29/2016 - 11:57

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Jeannie Miller (third from left) with students Wajih Ahmed, Oona Nadler and Muhammad Ansab (Photo by Diana Tyszko)

Peter Boisseau

Author legacy

Peter Boisseau

Topic

Our Community

Faculty of Arts & Science; Research; Faculty & Staff

Jeannie Miller is making a big impact with a new perspective on some very old prose.

Miller, an assistant professor in the department of near & Middle Eastern civilizations, is working on a manuscript examining The Book of Animals by al-Jahiz, a ninth-century Arabic writer and polymath. Al-Jahiz saw himself as a theologian and natural scientist, but is often miscast because of the risqué nature of some of his prose.

“He sometimes gets placed as an entertaining literary figure, as opposed to a religious thinker, which I think is wrong,” says Miller, whose forthcoming book is entitled Performative Inquiry: How Rhetoric Produced an Abbasid Natural Science.

“These things were not necessarily opposed in the ninth century. By classifying al-Jahiz that way, one misrepresents the history of Islam by removing his entertaining work from that history.”

The Book of Animals was written “in service to God,” says Miller, and partly in response to Aristotle’s biology books. In it, al-Jahiz exhibits an “exciting and very inclusive” approach to humanity. Using pigeons as an analogy, for example, he observes that there seem to be many natural forms of sexuality, including homosexuality in males and females, as well as varying preferences regarding domination.

“Much of the Book of Animals is dedicated to arguing against people who thought that exceptional people and animals were monstrous or scary. Like most intellectuals of his time, he was an elitist and did not treat everyone equally — but he did treat all kinds of people as natural results of God’s creation,” says Miller, a former Fulbright scholar who joined the U of T faculty in 2013 after doing her undergraduate degree at Harvard University and her doctorate at New York University.

“I’ve always been interested in works that blend literature and science. For this project, I wanted to set aside modern divisions between science and literature, and between entertainment and religion, and just ask what al-Jahiz was trying to accomplish, and why he felt it had to be done this way,” Miller says. “He says his goal is to show how wondrous divine creation is, but was it really necessary to spend half a volume citing poetry about excrement and the perversions of the dung beetle?”

Miller’s book will make the case that in fact al-Jahiz did think it was necessary to examine feelings of repulsion and attraction, through poetry and rational argument, in order to fully understand the place of humans in God’s creation. “He wanted to bring together every way of knowing and understanding the world God created, including our innate reactions of disgust or pleasure.”

This was very likely a product of his exposure to the rhetorical debates practised by his theology teachers, adds Miller. “They weren’t just engaging in dialectic — they were also citing poetry, and recounting anecdotes to make points about the natural world.”

Paper had been introduced to the Muslim world around 800 AD and al-Jahiz responded to this new technological opportunity by writing large compilations as a way to preserve, defend, and theorise some of those rhetorical debate practices.

Miller notes al-Jahiz was a foundational writer in the “adab” genre, and that even though this type of writing was often full of “obscene stories and dirty jokes,” it was also often religious in nature. In fact, many adab writers were religious scholars.

“Adab texts are obscene and they are religious, and I don’t think people felt a lot of problems with that at the time,” says Miller, who studied Arabic in Ethiopia and in Syria just before the war.

Modern editions of those texts, published both by European and Arab presses, have at certain times removed passages deemed too sexual or homoerotic, but this didn’t happen to al-Jahiz, she says.

Arabic texts are worthy of being studied with the care, attention and creativity afforded English literary heritage, adds Miller, who also speaks some French, Italian, German and Hebrew.

“Just allowing English speakers access to the richness, complexity and diversity of the Arabic heritage is a small contribution to combatting Islamophobia.”