The biological blowhole is what we typically see in whales, dolphins, and porpoises. The blowhole is the hole at the top of the cetacean's head. (example at left is a bottleneck Dolphin) This is the hole through which the animal breathes air. When a cetacean reaches the water surface to breathe, they will forcefully expel air through the blowhole, as with the whale in the photo to the right. However, not only is air expelled, but mucus and nitrogen from the animal's metabolism, which has been stored in the whale while diving is expelled from the hole. The exhalation is released into the comparably lower-pressure, colder atmosphere, and any water vapor condenses. This spray, known as the blow, is often visible from far away as a white splash, which can also be partially caused by water resting on top of the blowhole.

There are different kinds of geological blowholes.  One is created from sea caves that have grown landwards and upwards into vertical shafts that are exposed towards the surface. As water is forced into the lower portions of the caves, the caverns fill and eventually the water is forced out the top opening of the blowhole, as seen in the photo to the left. Another geological blowhole is the rare feature in which air is either blown out or sucked into a small hole at the surface due to pressure differences between a closed underground cavern system and the surface. The blowholes of Wupatki National Monument, like the one with the girl in the photo to the right, are examples of such a phenomenon. It is estimated that the closed underground passages have a volume of at least seven billion cubic feet, which creates wind speeds of almost 30 mph. In the case of this video, I would say that it fits quite well in the category of a man made geological phenomenon.  Thus the term, "A Manhole Blowhole. 

As for the video below, it was filmed on I-35 at 35th Street in Minneapolis by the Minnesota Department of Transportation. The video is actually two videos spliced together, because it happened twice. The first part was filmed on July 3, 1999 and the second part was filmed 5 years later on July 11, 2004. Another interestingly part of this manhole blowhole incident is that they both happened at about 5:30 in the morning.

The first one with the car being damaged is all over the web and the claim is that it took place in Calgary Canada. However, when I found the second one I realized that it was the exact same place as the first. You can read the article about the second video on the StarTribune.com web site archives. As of right now, this is the only video that has both incidents included in it. Give it a day or two an I am sure it will be copied.

One more thing before you watch the video. The article I linked to addresses the fact that the city and the state were in the process of working on the problem in 2004. Something I keep asking myself every time I watch the video is why were all the people flying down the highway as if they were oblivious to the danger? Well without further a due, I present to you a Manhole Blowhole.