NASA announced on Thursday that its MESSENGER spacecraft has found new evidence that flood volcanism has been widespread on Mercury.

New data from the spacecraft reveals that 6 percent of Mercury’s total surface is covered by volcanic plains.

“Analysis of the size of buried ‘ghost’ craters in these deposits shows that the lavas are locally as thick as 2 kilometers” (or 1.2 miles), James Head of Brown University, the lead author of one of the reports published in Science, said in a press release. “If you imagine standing at the base of the Washington Monument, the top of the lavas would be something like 12 Washington Monuments above you.”

Head said the deposits appear typical of flood lavas, containing huge volumes of solidified molten rock similar to those found in the Columbia River Basalt Group.