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Ever Get That Sinking Feeling?

Mexico City was built basically on a flat island in the middle of a lake. Frequently, the city floods during the June-to-October rainy season.

But, the real problem is that Mexico City is sinking at a rate of 6-8 inches per year. This shrinkage is due wells drawing out underground water to meet the needs of a growing population of 18.7 million people.

Some effects of the shrinking:

  • Landmarks anchored to the bedrock now seem to "thrust" skyward
  • Fourteen steps have been added to the base of the Independence Monument (built in 1910)
  • A water pipe originally installed at ground level (1934) beside the Revolution Monument now rises 27 feet in the air
  • The original ground floor in the Palace of Fine Arts is now a basement.
  • The Insurgentes Traffic Circle, a main intersection built on underground pylons (1970), is now twelve feet higher than the streets feeding traffic into the Circle
  • Holy Trinity Church (17th-century) lists to one side and is sinking faster than the bordering streets...to attend mass, people have to climb down a seven-foot stairway to the door.
  • Due to the sinking streets, the city's sewage tunnels are so tilted that they actually run backwards.
Your "Rediculous" Task: The Torre Mayor, a 55-floor skyscraper with a height of 225 meters, is the tallest building in Mexico City. Based on the given data, when will this building be submerged or below ground level?

Note: Mexico City is not alone with this "sinking" feeling. Six additional cities face the same problems, either due to a sinking base or rising water levels on shorelines.

Source: Adapted from Reader's Digest Book of Facts, 1987, p. 154.