Lush rolling hills cradle the still waters of Romania’s Saint Anne Lake, which rests in an ancient crater from the eruption of the Ciomadul volcano. The peak last blew its top some 30,000 years ago, and its lengthy quiescence has led many to presume the volcano would not likely erupt again.

But as it turns out, the rocks miles below this serene scene may be stewing with a surprising amount of heat. A study recently published in Earth and Planetary Science Letters suggests that the system likely harbors between five and 14 cubic miles of magma, a maximum volume more than that of 20,000 Great Pyramids of Giza.

To be clear, this does not mean an eruption is necessarily in the