Would one ocean pour into the other if the locks on the Panama Canal were blown? If not, let's say a mile-deep trench were dug from coast to coast. Would there be flooding then, huh?
No, you mollusk. They don’t have locks on the Panama Canal because one ocean is higher than the other, they have them because the land is higher in the middle — 85 feet higher, to be exact. As I have explained in the past, the level of the sea is more or less uniform throughout the world, making the concept of “sea level” possible.
But that’s not to say you wouldn’t get any flow from one ocean to the other if somebody dug your “mile-deep trench” from coast to coast. Scientists studying the feasibility of a sea-level canal (not a mile deep, but deep enough) have found that the Pacific at Panama is about eight inches higher than the Atlantic on average due to currents and such. In addition, tidal variation on the Pacific side of Panama is much greater than on the Atlantic side — 20 feet vs. 1 foot.
That means the Pacific would flow into the Atlantic through the sea-level canal, producing currents that could reach nearly 6 MPH. While that wouldn’t cause flooding, it would definitely complicate navigation.
But that’s the least of the problems a sea-level canal would present. It would also allow Pacific and Atlantic marine species to mingle, with unpredictable but probably bad consequences for the environment. Worse, constructing it would require either (1) tens of billions of dollars or (2) nuclear explosives. So don’t expect it any time soon.
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