The Temperature Changed
They had underestimated the rate at which the temperature would rise, so they were caught off guard. By the time they got close to the target, the temperature in the hole had reached 180 degrees Celsius (356 degrees Fahrenheit). These are temperatures that are 80 degrees Celsius (176 degrees Fahrenheit) hotter than they had anticipated!
There Was More
It wasn’t the only thing that happened. The researchers also discovered that the granite at such depths was significantly thinner than they had previously believed. Consequently, when exposed to higher temperatures, it reacted in unexpected ways.