Cross-section of littoral lava fountain, Kīlauea, Hawai‘i

Cross-section of a littoral lava fountain caused by partial collapse of a lava delta. A partial collapse of a delta's leading edge may significantly fracture the solidified rock around an active lava tube, which allows seawater to seep into the tube system. When seawater and lava mix within the confines of a lava tube, pressure may build to cause sustained explosions that blast a hole through the roof of the tube and send lava fragments several tens of meters (yards) into the air.