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May 21, 2012 | by  | in Opinion |
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Science: What’s It Up To?

CSI: Geology

Towards the end of WW2, Japanese military scientists made use of a reliable, high speed current of air that they had discovered flowing at high altitude over their country (now called a jet stream).

They used this current to carry large balloons across the Pacific, travelling a distance of more than 8,000km in about
3 days. The balloons were equipped with incendiary and high-explosive bombs, the plan being for them to land in the United States, killing people, destroy buildings and start forest fires.

The hydrogen balloons expand and rise as they are warmed by sunlight; then fall at night as it gets cooler. The engineers devised a system to discard ballast, driven by an altimeter. When the balloon descended below an altitude of 9 km, the altimiter electrically fired a charge to cut loose sandbags. Similarly, when the balloon rose above about 11.6 km, the altimeter activated a valve to vent hydrogen. The hydrogen was also vented if the balloon’s pressure reached a critical level.

This was a pretty badass idea, but fortunately for the Americans the jet stream doesn’t flow in a direct line. Balloons aimed at California spread right from Alaska to Mexico. Of the ~9000 launched, only 300 were discovered in the USA, and only one caused an explosion that killed anyone (6 people on a picnic).

The Americans were mystified though. They didn’t know the jet stream existed, and the notion that they were coming all the way from Japan seemed preposterous. There were two theories about the source of the fire balloons. Either they were being made by Japanese in POW camps in California, or they were being launched from Japanese submarines off the coast.

In order to discover the source, sandbags recovered from the balloons were taken to the Military geology unit of the US Geological Survey. They put the boys to work, examining the chemical composition and the presence of diatoms and other microorganisms present in the sand. From their analysis, they determined that the sand was not from anywhere in America. Neighbouring pacific islands were ruled out until finally, using information from Japanese geological publications published before WW2, it was determined that the sand was from Japan. They were even able to pinpoint the specific beaches the sand was from. Spy planes took photos of these beaches and discovered factories operating nearby, which were bombed by the air force.

This article is less about US foreign policy and more about how cool geology is–they were able to look at a bag of sand and tell which beach (out of any in the world) it was from.

In case you were confused: Geology ≠Geography.

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