A potentially greater hazard at Mauna Loa is a sudden, massive collapse of the volcano's flanks, like the one that struck the volcano's west flank between 100,000 and 200,000 years ago and formed the present-day Kealakekua Bay. Deep fault lines are a common feature on Hawaiian volcanoes, allowing large portions of their flanks to gradually slide downwards and forming structures like the Hilina Slump and the ancient Ninole Hills; large earthquakes could trigger rapid flank collapses along these lines, creating massive landslides and possibly triggering equally large tsunamis. Undersea surveys have revealed numerous landslides along the Hawaiian chain and evidence of two such giant tsunami events: 200,000 years ago, Molokaʻi experienced a tsunami, and 100,000 years ago a megatsunami high struck Lānaʻi. A more recent example of the risks associated with slumps occurred in 1975, when the Hilina Slump suddenly lurched forward several meters, triggering a 7.2 earthquake and a tsunami that killed two campers at Halape.