alt Hacker NewsI found "inflate like a balloon" a bit confusing/misleading. it's more like the fracture in the rocks expands(slightly) due to the pumping of water- and when the pump is turned off, the fracture goes back to a normal position pushing the hot water up. I am not an expert but I am really bamboozled by the reliability of this bc I imagine the rock/fracture will have to give away after some time(permanent rupture) or they will have to keep expanding the fracture.
It's a crack, not a void or a cave. The crack doesn't actually have significant volume (it probably does but all things considered it's tiny). It's like the space between two stacked bricks. Or maybe it's some permeable material like brick then sand then brick. You pump that full of water and you're basically lifting the bricks with hydraulic pressure. Gravity is what squeezes it back out.