Believe it or not, but according to the Guardian, Mexico City has sunken by 10 meters (about 33 feet) over the last century - much worst than Venice which is famously sinking at about 1 centimeter (or a third of an inch) a year.
This has become a very big problem for the massive city with no easy way to fix it. Some consider it largely unstoppable as the aquifers have become depleted and the lakebed on which the city is built becomes increasingly dry. Today it is one of the cities of the world that is sinking before Venice.
The Lake Texcoco
It all started way back when the Aztecs (or Mexica) were looking for a new place to build a city and they found a small island in a lake. It was a great place to defend from attack and they decided to build their city there. But that island was in a lake that had formed in a volcanic crater and, while defensible, it was not great to build on.
While one can point a finger at the ancient Aztecs for choosing a crater lake as the place of choice for their once gleaming city, things got a lot worse after the Spanish took over in 1519.
- 1519: Date The Spanish Took Over Tenochtitlan
After conquering and destroying the once-proud Aztec city of Tenochtitlan, they set about building the modern city of Mexico City on its ruins. Instead of the massive Aztec Templo Mayor (the ruins of which one can see today), the Metropolitan Cathedral arrises today.
They set about filling in the lake and sinking deep wells to bring up water from the underground aquifers. The Guardian quotes Eddie Bromhead, a geotechnical engineer at Kingston University as saying.
"Everywhere they pumped up groundwater from the boreholes, the ground sank. Without the water there, the sediments that the city was built on compressed a lot more"
Draining Of Lake Texcoco
The lake that Tenochtitlan was built in was called Lake Texcoco. But there are predictable problems with building a city on a lake. One of the most pressing issues was that Mexico used to suffer from periodic floods. The city flooded in 1604 and again with a more severe flood in 1607.
- Flooding: Mexico City Was Subject To Flooding
In response, a drain was created to control the level of the lake, but in 1629 another flood kept most of the city underwater for five years.
It was debated if they should move the city, this was their chance. But instead, the Spanish decided to stay and they eventually drained the lake through channels and a tunnel. But even then the city continued to flood as by then most of the city was under the water table. Flooding wasn't completely controlled until the last 50 years.
- Relocating The City: Early On There Was Debate About Relocating The City
Consequences of Draining The Lake
But there have been massive ecological consequences of draining the lake and building the city on the former lake bed. Today parts of the valley have become semi-arid while Mexico City suffers from a lack of water having depleted the aquifer and that is sinking the city. During earthquakes, the city has become prone to liquefaction
- Remnants Of Lake Texcoco: Xochimilco, Chalco, Zumpango, and An Area Surrounded By Salt Marshes 2.5 Miles Each of Mexico City
- Sunken: Around 10 Meters (30 Feet) over the Last Century
And then the city's population took off and boomed, but so too did the demand for water. It is now believed that the aquifer beneath the massive metropolis is in danger of collapse.
Sinking Mexico City Today
The lastest on the line of mistakes has been to build the heavy high-rise buildings when the city suddenly received masses of immigrants swelling the population to about 20 million.
- Population: 20 Million For Greater Mexico City
These heavy buildings are compacting the soil, while the water is being removed underneath them. The end result is a sinking Mexico City. Today Mexico City is sinking, and sinking in a relative freefall into the volcano on which it is built.
This has created a great mess and solving the problem is tricky to say the least.
- Solution: There Is No Easy Solution To The Problem
It was never a great 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 on earth. Moving the city is hardly practical anymore.
In some places, the land has been compressing at around 50 centimeters a year. Even if the sinking can be stopped, it can't be reversed.
The Guardian went on to quote Eddie Bromhead
"As the years pass, they could gradually replace badly founded buildings with better ones. Or, of course, they could just get on with it and live with crooked buildings."