Jan
25
2010

Meteor impact may have intiated plate tectonics

Was a bolide the cause for plate tectonics?
Was a bolide the cause for plate tectonics?Courtesy Navicore via Wikipedia Creative Commons
Recently, geologist Vicki Hansen, a professor of earth and planetary sciences at the University of Minnesota-Duluth, proposed a hypothesis that plate tectonics were triggered by ancient bolides crashing into Earth.

Plate tectonics arose from Alfred Wegener’s observations that some continents appear to fit together like puzzle pieces and at one time probably made up a single land-mass he named Pangaea that broke up and drifted apart. It was a theory dismissed by most geologists at the time, and Wegener himself was unsure how the process took place (he proposed magnetism or centrifugal force). It wasn’t until the 1960s, more than 30 years after Wegener’s death, that the theory gained wide acceptance. Today, scientists point to convective heat in the Earth’s mantle as the driving force that causes continental drift and sea-floor spreading. As new material is being added along mid-oceanic ridges, older crust is being pushed into other plates in a process called subduction, where one crust sinks beneath another and is remelted back into the mantle. It’s along these boundary zones where the plates collide that most of the world’s earthquakes and volcanoes occur, and where mountain ranges rise up. But what started the process? Why would Pangaea suddenly break up into pieces and begin drifting apart?

Hansen theorized that early in Earth’s history - perhaps as much as 2.5 billion years ago - impacts from large extra-terrestrial objects could have been the catalyst for two prime elements of plate tectonics: the spreading out of new crust, and particularly subduction. Since numerous impact craters can be found on Mars and on the Moon, it’s a good bet that Earth suffered a similar steady barrage of meteor impacts in its formative years. According to Hansen, the Earth’s crust at the time was more uniform in thickness, except in certain zones where mantle heat rising up from below would have caused it to thin.

A meteor or asteroid (one large enough to create a 600 mile-in-diameter crater) slamming into one of those weakened zones could have caused magma to erupt to the surface as flood basalts that would spread out and eventually push against the sides of the crater where they would begin subducting back down into the mantle. Such impacts could have happened several times around the world, enough to put the process of plate tectonics into motion.

Professor Hansen’s theory was first published in Geology magazine, but the study has reached the popular press. I came across it in the most recent issue of Science Illustrated, an interesting and jammed-packed-with-science publication new to me that I found at Barnes & Noble.

Professor Vicki Hansen webpage
UMD Planetary Processes Lab
More about plate tectonics

Your Comments, Thoughts, Questions, Ideas

Anonymous's picture
Anonymous says:

From The Space Review.com:

Louis P. Quinn · 19 hours ago

In reference to the plasma fireball produced by a large Near-Earth Object. I argue that if an impact is anywhere long the north to south magnetic lines that cross over the continental United States it will interrupt those lines. Because of (E3) coupling it would make the continental United States a much bigger impact target than most people assume.

A big enough impactor can produce a very large ball of plasma. A big ball of plasma will divert a section of the earths magnetic field. It is like plucking a string on a guitar. The United States electrical grid will supply the reverberation. There are generators out there that will take many years to replace. That is if we can get another country to build them. Our industrial capacity might be reduced by more than 50%.

For Geomagnetic Storms we may have enough warning to shut the grid down and isolate the irreplaceable components. In case of a Near-Earth Object we can only do this only if we know when it will impact.

In the Final Report of the National Academies Near-Earth Object Surveys and Hazard Mitigation Strategies strongly argues that we may not get this shutdown warning because of a lack of funding for/from NASA. The money would be for building and operating the telescopes that would search for these infrastructure killing rocks.

posted on Tue, 01/26/2010 - 10:56am
Heidi.l's picture
Heidi.l says:

Who wrote the article in Science Ilustrated. My sixth graders need it for a works cited page. Unfortunately the magazine was returned to the library.

posted on Wed, 02/23/2011 - 3:55pm
mdr's picture
mdr says:

Heidi - Unfortunately, I no longer have the issue. I did find an online site where you can view the content of back issues of Science Illustrated (zoom-ins of pages is limited), but oddly the article doesn't seem to list any author, at least none that I could find. In fact, none of the articles I looked at seem to list an author. Nor does the magazine's masthead list contributing writers. It may be that the magazine's text is supplied by the editors. Anyway, click here for the link directly to the issue that you're interested in (Jan/Feb 2010). Maybe you'll have better luck finding a credit.

posted on Thu, 02/24/2011 - 12:47am
bucky's picture
bucky says:

I first saw the puzzle-type connection between Africa and South America when I was seven (in 1959). My teacher scoffed me.

Now I see the possible connection with meteors striking earth during the period of the separation of Panagaea.

I also questioned the possibilities of tsunamis in areas which were not considered vulnerable. Now, those areas are under scrutiny.

I am not a geology major (Bachelors in Business), but maps of the earth (past and present) catch my attention when questions arise about why earthquakes and other catastrophies occur in certain regions.

My query is aways WHY they happened.

posted on Tue, 01/24/2012 - 9:04pm
mdr's picture
mdr says:

I remember thinking the same thing about the continents fitting together when I was about that age (I don't think we were alone). Unfortunately, Alfred Wegener's radical idea of drifting continents was pooh-poohed and suppressed for decades until around the mid-60s when scientists finally saw it as a critical part of an all encompassing answer to many problems vexing geologists.

posted on Wed, 01/25/2012 - 5:57pm
G.C. Herman's picture

Great ideas, but I think this is just the tip of the iceberg. Evidence is mounting that shows where large hyper-velocity boilde impacts on Earth have fragmented crustal plates and influenced subsequent plate dynamics to this day. Im just saying...see impacttectonics.org

posted on Fri, 07/13/2012 - 7:54pm
Dr. Kenneth Thronton's picture
Dr. Kenneth Thronton says:

Don't assume that magnetics play the same role 2.5 million years ago as they play today.

posted on Mon, 07/15/2013 - 7:20pm

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