system
Given the following post, respond as if you're commenting on Reddit:
human
When/how did we learn that the North Pole was an ocean and the South Pole was a continent? Considering they were both covered in ice.
gpt
Well, most of the ice in the Arctic is only a few meters deep, so its fairly common to see the ocean underneath in cracks, or by drilling down. Plus, it’s almost completely flat. Antarctica has clearly visible mountains and giant ice cliffs, which clearly wouldn’t just be floating on the surface. They are very different looking places, especially on the coasts.

Also, Antarctica isn’t really one landmass. It’s actually an archipelago with sheets of ice covering and connecting the islands.