Where were you 200 million years ago?

Where were you 200 million years ago?

A paper published recently in the journal PLoS ONE focuses on an online tool showing the location of any place on earth at any point up to two hundred million years ago. This collaboration between geophysicists from Utrecht University and Sebastiaan van Schaik at the Oxford e-Research Centre, allows people to compute their paleolatitude: the latitude of a location up to 200 million years ago, via a readily accessible tool at http://www.paleolatitude.org.

The website calculates the position of location at a point in time as compared to the poles and equator. For example, approximately 140 million years, Western Europe was located roughly at the latitude where North Africa currently is, while the Northern tip of Norway could be found where the Netherlands is today. Two hundred million years ago Australia was on the South Pole. 170 million years ago Oxford e-Research Centre would have been at the same latitude as the north of Algeria is today. This and more information can be found on the Paleolatitude.org website.

For students it is a fun and engaging way to discover geological history, for example, to find out where their home was located two hundred million years. Using fossils, scientists are able to reconstruct past climates. With greater accuracy than ever before they can discern whether climate change was caused by plate movement or global trends at a range of locations.

Two mechanisms

"Relative to the rotation of earth’s axis, there are two mechanisms by which a continent does not remain forever in the same spot," says lead author Dr. Douwe van Hinsbergen, Geoscientist at the University of Utrecht. "One is plate tectonics, the other is True Polar Wander."

Out of balance

True Polar Wander (TPW) is a phenomenon that has long been known to science, but its importance has only recently become more appreciated in climate reconstructions. Because the earth's outer core consists of liquid metal, there is little friction relative to the crust and mantle. The surface can become unbalanced, for example, when the tectonic plates begin to slide over each other. "Just as a spinning top gets out of balance when one side is heavier than the other," says Van Hinsbergen.

Different reconstruction techniques

Van Hinsbergen says: "Plate reconstructions are usually created by scientists trying to find out how the movements in the mantle drives plate tectonics, and how they can cause earthquakes or mountain ranges to form. For those reconstructions True Polar Wander is not important and the effects can be ignored. However, for climate studies it is very important that we take plate reconstructions into account in relation to the effects of True Polar Wander. Here a change of latitude of between 10 to 20 degrees (1100 to 2200 kilometers) effects time scales in the region of tens of millions of years." In order to avoid confusion with other reconstructions, Paleolatitude.org was designed specifically for climate reconstructions.

Big step for climate studies

Van Hinsbergen believes that this is a big step for climate studies: "If you take Greenland’s current latitude with respect to the location of the Earth's mantle and reconstruct it as of tens of millions of years you might conclude that there has been a massive global cooling. However, if you reconstruct Greenland relative to the rotation of the earth’s axis, as you do when you consider the paleoclimate, you see Greenland has moved more than a thousand kilometers to the north, and that a substantial portion of the cooling in Greenland does not come from global cooling, but from plate shift.

The new insights are also important for reconstructing the effect of CO2 on the climate. Co-author Appy Sluijs: "In the past the concentration of CO2 in the atmosphere varied by natural causes. We reconstructed the climate from as many places as possible on earth to see how much effect CO2 had on the climate. Via accurate location provisions on the new website, we can more accurately determine how strongly CO2 effected the global climate.

Stimulating

While Paleolatitude.org is still in development, it is available for use. "I hope it encourages students and teachers to learn more about our geological past" says Van Hinsbergen.