Why do roads buckle when temperatures rise?

By Andy Kalmowitz, AccuWeather staff writer

Dramatic photos often emerge amid heat waves, including people frying eggs on sidewalks and signs melting. But some of the most epic photos are of roads buckling due to extreme temperatures.

According to the Nebraska Department of Roads (NDOR), the main factor behind roads cracking is a process known as “thermal expansion.”

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"A pavement blow-up occurs when the roadway surface expands at a crack or joint where moisture has seeped in, NDOR states on their website. "That crack weakens the pavement and the heat causes the pavement to buckle and warp. This usually occurs on very hot afternoons, as the maximum temperature for the day is reached, typically during afternoons with 90-degree or hotter temperatures."

The reason this happens is due to the way roads are built — in layers.

According to Rhino, a company who’s sole purpose is repairing roadways, as temperatures change, road surfaces expand and contract.

“Concrete is designed in slabs and designed to focus this movement at the joint between slabs. Lean mix and continually reinforced concrete also focuses movement in concentrated points," their website states. “Asphalt reacts differently to temperature changes, expanding and contracting evenly over the entire surface area.”

Cars pass by a section of buckled highway in Decatur, Ga., Monday, April 17, 2017. (Photo courtesy of Steve Power via AP)

It is this incompatibility between concrete and asphalt to react similarly that causes asphalt overlays to crack and buckle.

“Couple this with variations in which the different layers of the road surface heat up from the sun, the lower layers expand at a slower rate to the surface ones, and it is no wonder that a road surface cracks as it does,” the website reads.

These buckling roadways can be very dangerous for drivers and can cause cars to go airborne for a few feet, as well as crash.