Impact of the 2004 Boxing Day tsunami in Thailand. Credit: David Rydevik

I occasionally write about the development of new technologies that remind me that we really are living in “the Future“, but how about one that happened nearly 70 years ago?

In a little-noticed story last week, The Telegraph reported that during World War II, the United States undertook an operation code-named Project Seal to build a weapon of mass destruction that would have created a tsunami to flood the enemy’s coastal cities. The files relating to Project Seal were declassified in 1999, but they have received renewed attention after being rediscovered by New Zealand author and filmmaker Ray Waru.

Could it have worked? The difference between a tsunami and a normal, wind-driven wave is not height. (Many tsunamis are only inches high, and wind-driven waves can be over 100 feet high.) It is the amount of water that is on the move. A wind-driven wave moves only the top layers of the ocean, while a tsunami occurs when the water is displaced from top to bottom. This usually happens when an earthquake moves a large chunk of rock upward, displacing the water above it, as in the 2004 Boxing Day tsunami. However, the 1958 Lituya Bay megatsunami (the tallest in recorded history) was caused by a landslide, and the same thing could happen in the case of an asteroid impact. Because these events move so much more water, it all comes up onto the shore like a tide.

This was the principle behind Project Seal. Just like an earthquake or a landslide, a large enough explosion could also displace enough water to create a tsunami. It would work even better if there were several explosions in a line to build up the wave, like water sloshing in a bathtub. In 1944 and 1945, 3,700 bombs were used to test this principle, but the results were not encouraging. The weapon would have needed 2,000 tons of explosives lined up just five miles from the target city, something that would not be very practical in an active war zone.

In the end, the atomic bomb filled the weapon of mass destruction role far more efficiently than the “tsunami bomb” ever could have, and the project was shelved, but that it ever existed at all proves that people have been thinking seriously about science-fiction-style technologies for a very long time.