These 7 animals have made some of the greatest journeys on Earth

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Earth is enormous.

With 197 million square miles of surface area, our planet is a massive obstacle course of geographic barriers that force most species to stay put.

Yet these barriers have meant nothing to some animals. They've traversed Earth with aplomb - dangerous oceans, stormy weather, and moving continents be damned.

Here are seven of the most fearless globe-trotting creatures that have flung themselves across our world, some through unstoppable determination, others by pure chance.