[blackdog]

Metropolitan cities have quite a few minor blasts quite frequently. All the high voltage lines and such run under the streets and sidewalks. Natural gas, methane, and such will pop off when electrical connections deteriorate and overheat with an arc blast.

Hint......Don't let fido walk NY City sidewalks. Quite a few doggies get killed from stepping on metal manhole covers each year.

[gleeaikin]

A while back Washington, DC had exploding manhole covers. I think some went as high as 150 feet. No one injured as I recall, but many frightened.