A former NASA employee has released a fascinating animation which shows how the look of the planet would change if all the oceans—which cover three fifths of the surface—gradually drained away.
Planetary scientist James O'Donoghue—who now works at the Japanese Space Agency (JAXA)—updated a 2008 video which was made by NASA animator Horace Mitchell, Business Insider reported.
In the initial few seconds of the animation, the first land that emerges from under the sea are those regions surrounding the edges of continental landmasses—what are known as "continental shelves."
These shelves make up around 8 percent of the total area covered by the Earth's oceans. They are mostly visible after a drop in sea level of around 460 feet, apart from those in the Arctic and Antarctic regions where the shelves are located at greater depths.
"I slowed down the start [of the video] since, rather surprisingly, there's a lot of undersea landscape instantly revealed in the first tens of meters," O'Donoghue told Business Insider.
"The shallow seas fade quickly between the U.K. and Europe, Russia and Alaska and Asia/Oceania and Australia, so quite instantly we can
appreciate how water only barely separates them," he told Newsweek.
Some of these continental shelves were exposed thousands of years ago, and ancient humans used them to cross into unexplored regions. For example, experts think that populations which would become the first Americans traveled over this the land bridge that once connected eastern Siberia to Alaska around 16,000 years ago.
"When the last ice age occurred, a lot of ocean water was locked up as ice at the poles of the planet. That's why land bridges used to exist," O'Donoghue said. "Each of these links enabled humans to migrate, and when the ice age ended, the water sort of sealed them in."
By the point in the animation where ocean levels have dropped between around 6,500 and 9,850 feet, the mid-ocean ridges begin appear. According to the National Oceanic and Atmospheric Administration (NOAA), this continuous range of underwater volcanoes is effectively the "most extensive chain of mountains on Earth," stretching more than 40,000 miles.
Mid-ocean ridges form along the boundaries of tectonic plates which are moving away from each other. As the plates separate, molten rock rises up from beneath the planet's crust, which then cools, creating the underwater mountains.
Even though this ridge system is vast, scientists still know very little about it and detailed explorations—using submersibles and remotely operated vehicles—have so far been limited to a tiny area.
After sea levels have dropped by nearly 20,000 feet in the animation, the majority of the ocean disappears, apart from the deepest ocean trenches. These include, the Mariana Trench in the western Pacific which extends to an incredible depth of nearly 36,000 feet—a distance roughly equivalent to the cruising altitude of most commercial planes flying above the Earth's surface.
"I like how this animation reveals that the ocean floor is just as variable and interesting in its geology as the continents," O'Donoghue said.
This article was updated to include additional comments from James O'Donoghue.
