Media Releases

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

June 14, 2016

Toron­to, ON – Super-com­put­er mod­el­ling of 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.

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.”

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Philip Heron
Depart­ment of Earth Sci­ences
Uni­ver­si­ty of Toron­to
Tel: 0044–7857688947

Rus­sell Pyskly­wec
Depart­ment of Earth Sci­ences
Uni­ver­si­ty of Toron­to
Tel: 416–978-3021 (W)
Tel: 416–537-2683 (M)

Sean Bet­tam
Com­mu­ni­ca­tions, Fac­ul­ty of Arts & Sci­ence
Uni­ver­si­ty of Toron­to
Tel: 416–946-7950