View into the crater of Pu`u `O`o cone looking southwest. The active vent within Pu`u `O`o (inner crater from which gas is escaping) is about 60 m in diameter. For the past week lava has intermittently spilled from the vent to partly cover the crater floor with new lava and drained back to a depth of about 10 to 15 m. This inner crater vent originated as a spatter cone in May 1997. Since then, the cone subsided to form an inner crater within Pu`u `O`o and then slowly enlarged to its current size.