CNN reports that a study based on the city of Chicago showcased that the land shifting underneath urban settlements can have negative effects on buildings and infrastructure, such as pipelines or the metro system, where is exists.

The phenomenon is also known as "subsurface heat islands" and it is caused by many things, such as the road and buildings heating up during hot days, such as we encounter this summer, but also due to stress and heat coming from the metro system. In Europe, this summer is set to be one of the hottest in many years and this is bound to affect not only the infrastructure, but also city dwellers.

Lead study author Alessandro Rotta Loria, from Northwestern University in Evanston, Illinois, said that "the denser the city, the more intense is underground climate change."

The soil and all types of construction materials deform when exposed to intense heat, which causes ground instability, experts say.

"Deformations caused by underground climate change are relatively small in magnitude, but they continuously develop. Over time, they can become very significant for the operational performance of civil infrastructure like building foundations, water retaining walls, tunnels and so on", Rotta Loria explained.

Underground climate change has been studied by experts for the past 25 years-or-so and during that time, they discovered that such events contribute to water contamination and can create problems for metro systems and its passengers, as infrastructure wears at an accelerated pace.

For the study, 150 temperature sensors were installed across Chicago, above and under the ground, in various places. Some were implemented in Grant Park, as well, so that researchers could determine how heat affects an unbuilt area with lots of green spaces.

Three years after the study began, Rotta Loria and his team were able to determine that the temperature below the city ground was as much as 10 degrees Celsius warmer that what was found below the Grant Park. Over the course of 100 years, from 1950 to 2050, excessive heat could work on the underground at a rate that we can't perceive with our naked eye, but it definitely affects the infrastructure in a negative way, researchers say.

"It’s important to stress that underground climate change does not threaten the safety of people and does not threaten to collapse structures and buildings. It does pose a potential challenge for the functionality and the durability of structures, because excessive ground deformations can lead to distortion, tilting and potentially cracking", the lead study author said.

New buildings are not likely to contribute much more to the issue, Rotta Loria says, as they are built on modern standards and with efficiency in mind. As for old ones, we can also increase their energy efficiency through renovation, which would help maintain a more comfortable temperature on the inside, while the outside won't be as toasty, either.

The entire study, published in Communications Engineering, can be read here.