Fissures opened in the cinder-covered surface uprift from Pu'u 'O'o in July of 1985. Note that there are two parallel fractures about 50 m apart and forming a small graben. The next morning lava erupted out of the nearest fissure. The ground surface here is covered by a ~2 m-thick layer of Pu'u 'O'o scoria, and this helped to accentuate the cracks - similar to the way that a small hole dug into sand at the beach will eventually look quite large as sand slumps into the hole. In the case shown here the actual cracks in the rock under the scoria were only about 10-20 cm wide but so much scoria fell into them that they were wide enough to barely be jumpable.

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