World's tectonic plate movement mapped

Aug 25, 2014 by Geoff Vivian
The boundaries of the tectonic plates in the Earths crust, responsible for earthquakes and volcanoes. Credit: iStock

A group of geophysicists is testing the hypothesis that the rate of "supercontinent assembly"—or tectonic plate movement—changes over time.

Study co-author Professor Sergei Pisarevskiy says is the study of the horizontal movement of over the Earth's surface.

"This is not uniform movement," he says.

"Sometimes there are periods where there was very quick movement all together globally, and sometimes very slow movements.

"We try to analyse that and to populate the mean angular velocity of the average plate movements on the surface of the earth."

He has come to the tentative conclusion that the average rate of tectonic plate movement does change.

"Right now for example it's slower than it was half a billion years ago—but approximately the same as it was one and a half billion years ago," he says.

"But there are many problems to be resolved before the final answer.

"It's sort of half guessing I would say at this stage."

He says beside the uneven level of the same analysis in different countries, he and lead author Kent Condie are addressing various other problems.

One is the inconsistent rate at which plates appear to move, both individually and relative to each other.

"For example Africa moved very slowly for the last few hundred million years, on the other hand India as you probably know moved very fast," he says.

"When you calculate the average movement … of the continents of the earth you cannot just average the movement, the speed of a continent like Africa and some very small block like Madagascar for example.

"They must be weighted, so we normalise the speeds by the area of that particular continental block."

"When talking about the , we also found some quieter periods, not exactly the periodicity but some maximums and minimums."

Another problem is the way in which evidence tends to deteriorate over time with more recent "overprints" creating statistical "noise".

"The older the rocks, the less information you will have," he says.

"This noise increases—going back in time it's more difficult to extract this information."

They are also contending with the phenomena of "passive margins" between plates.

One of these is thought to exist beneath the ocean south of Australia—it shows little or no for at least a billion years.

"There are no major tectonisms here or seismicity, it's just accumulations of sediments mostly," he says.

Explore further: Studies show movements of continents speeding up after slow 'middle age'

More information: Kent Condie, Sergei A. Pisarevsky, Jun Korenaga, Steve Gardoll, "Is the rate of supercontinent assembly changing with time?", Precambrian Research, Available online 4 August 2014, ISSN 0301-9268, dx.doi.org/10.1016/j.precamres.2014.07.015

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User comments : 6

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verkle
1.9 / 5 (7) Aug 25, 2014
A rather mushy article. Very few facts and data, and a lot of surmising and guessing.
Not much science here.

Solon
1 / 5 (5) Aug 25, 2014
How deep are these plates that move around?
Why does only Earth have tectonic plates, other planets have mountains and rifts but do not have tectonics, or did that happen on other planets billions of years ago?
Vietvet
5 / 5 (6) Aug 25, 2014
How deep are these plates that move around?
Why does only Earth have tectonic plates, other planets have mountains and rifts but do not have tectonics, or did that happen on other planets billions of years ago?


Know how to use Google?
alfie_null
5 / 5 (1) Aug 26, 2014
A rather mushy article. Very few facts and data, and a lot of surmising and guessing.
Not much science here.

The abstract, which contains more numbers, should have been appended.

Recalling your fundamentalist leanings, I'm guessing there are other unstated reasons you don't like the article.
tonymsm
1 / 5 (4) Aug 26, 2014
"...on the other hand India as you probably know moved very fast..."
Geologists say this because they will not accept the facts on the ground:
1. The Indian and Eurasian plates have the same magnetic signature, but that of the Tibet Plateau plateau differs. If the plates were originally separate, you would expect them to be different, with the plateau the same as Asia - but it isn't.
2. You can't make the hollow ellipse of the plateau by plate tectonic processes
3. If India was moving toward Asia, the Himalayas should curve that way too - but they don't.
The size of the plateau and the coincident dent in the Moho - filled with material of different magnetic signature, fit creation by rolling impact of a body the size of Venus, which also pushed up the surrounding mountain ranges and split the Indian Plate off from Eurasia, accounting for them having the same signature. The present subduction and uplift is just them trying to get back together.
OZGuy
5 / 5 (2) Aug 27, 2014
@tonyism
If a body the size of Venus rolled across any part of the Earth you'd get a bit more damage than a tectonic plate being broken. I suspect the Earth wouldn't survive as an intact planet.

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