Mexico City is built on the basin of an ancient drained lake, and today it sinks deeper and deeper into the lake bed.
Believe it or not, but according to the Guardian, Mexico City has sunk 10 meters (about 33 feet) over the past century – far worse than Venice which sinks about 1 centimeter (or a third of an inch) a year.
It has become a very big problem for the massive city with no easy way to solve it. Some consider it largely unstoppable as the aquifers have been depleted and the lake bed on which the city is built is becoming increasingly dry. Today it is one of the cities in the world that is sinking ahead of Venice.
It all started long ago when the Aztecs (or Mexicas) were looking for a new place to build a city and they found a small island in a lake. It was an ideal place to defend against attacks and they decided to build their city there. But this island was in a lake that had formed in a volcanic crater and, although defensible, it was not ideal for building.
While the ancient Aztecs can be blamed for choosing a crater lake as a favorite location for their once glittering city, things got much worse after the Spanish takeover in 1519.
- 1519: Date the Spaniards took control of Tenochtitlan
After conquering and destroying the once proud Aztec city of Tenochtitlan, they set about building modern Mexico City on its ruins. Instead of the imposing Aztec Templo Mayor (the ruins of which can be seen today), the Metropolitan Cathedral rises today.
They undertook to fill the lake and dig deep wells to raise water from underground aquifers. The Guardian quotes Eddie Bromhead, a geotechnical engineer at Kingston University.
“Wherever they pumped groundwater from boreholes, the ground collapsed. Without the water there, the sediment the city was built on got compressed much more“
Drying up of Lake Texcoco
The lake in which Tenochtitlan was built was called Lake Texcoco. But there are predictable problems with building a city on a lake. One of the most pressing problems was that Mexico suffered from periodic flooding. The town was flooded in 1604 and again with a more serious flood in 1607.
- Flood: Mexico City was flooded
In response, a drain was created to control the level of the lake, but in 1629 another flood kept most of the town underwater for five years.
It was debated if they should move the town, it was their chance. But instead the Spaniards decided to stay and they eventually drained the lake through canals and a tunnel. But even then the city continued to flood, as most of the city was then under the water table. Floods have only been completely brought under control in the past 50 years.
- Moving from the city: At first there was a debate about the relocation of the city
Consequences of lake drainage
But the drying up of the lake and the construction of the city on the former bed of the lake had massive ecological consequences. Today parts of the valley have become semi-arid while Mexico City suffers from a lack of water that has depleted the aquifer and is sinking the city. During earthquakes, the city became prone to liquefaction
- Remains of Lake Texcoco: Xochimilco, Chalco, Zumpango and an area surrounded by salt marshes 2.5 miles each from Mexico City
- Hollow: About 10 meters (30 feet) in the last century
And then the city’s population took off and exploded, but so did the demand for water. The aquifer beneath the massive metropolis is now believed to be in danger of collapse.
Mexico City shipwreck today
The latest mistake was to build the heavy high-rise buildings when the city suddenly welcomed masses of immigrants, bringing the population to around 20 million.
- Population: 20 million for Greater Mexico
These heavy buildings compact the soil, while water drains underneath. The end result is a shipwreck in Mexico City. Today Mexico is sinking, and sinking in relative free fall into the volcano on which it is built.
This has created a big mess and solving the problem is tricky to say the least.
- Solution: There is no easy solution to the problem
It was never a good place to build a city and yet the site is home to the largest city in North America with some 20 million people, making it one of the largest cities in the world. Moving the city is no longer practical.
In some places, the earth is compressing about 50 centimeters per year. Although sinking can be stopped, it cannot be reversed.
The Guardian went on to quote Eddie Bromhead
“Over the years, they could gradually replace poorly founded buildings with better ones. Or, of course, they could just go on and live with twisted buildings.”
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