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Figure 1. The collision of tectonic plates...Click to Enlarge ImageAt a rate of a few centimeters per year, the movement of continents is imperceptible to transient beings like ourselves. But over geologic time, the land masses that define the world of our senses have cruised around the globe, smashing together and ripping apart. Pangea, the supercontinent that broke up more than 100 million years ago, was only the most recent union of Earth's landmasses. Supercontinents and superoceans have been forming and disappearing for 3 billion years. But why do supercontinents split at one site and not another? The answer to this question is several hundred million years older than Pangea, dating back to the breakup of the previous supercontinent. The mountainous sutures of old continental collisions, it seems, carry the seeds of the next continental dispersion.

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