What caused the 7.8-magnitude earthquake in Turkey?

Turkey and Syria were hit by a massive 7.8-magnitude earthquake on Monday that caused widespread damage and left over 5,000 people dead. But what exactly caused the tremor and why was it so destructive?

Turkey is an "earthquake hot spot" because three different tectonic plates converge in the area: the Arabian, Anatolian, and African plates, writes The Washington Post. At the same time, the Arabian plate has been moving northward toward the Eurasian plate, causing Turkey to almost be pushed aside, NPR explains.

"Arabia has slowly been moving north and has been colliding with Turkey, and Turkey is moving out of the way to the west," Michael Steckler of Columbia University's Lamont-Doherty Earth Observatory told NPR. The plate has been moving approximately 11 millimeters per year, and has for thousands of years caused earthquakes in the area.

But scientists say that Monday's quake was one of the most powerful in almost a century and that it was also long overdue. "It was unusually quiet in the last century," commented Patricia Martínez-Garzón, a seismologist at GFZ Potsdam. The tremor was ultimately caused by the Arabian and Anatolian plates "sliding horizontally past each other" along the East Anatolia fault zone.

The quake was so deadly due to a number of factors, the Post explains. First, the earthquake was extremely large and spanned a wide geographic area. It also occurred close to the surface and impacted a number of major cities in the area, including Istanbul, where the population is high. 

"In the southeastern part of Turkey, they hadn't felt a strong earthquake in most people's lifetimes," said Stephen Hicks, a seismologist at University College London.