You will also examine a’a (or aa) lava at Sullivan Bay. This Hawaiian term describes when lava rapidly flows down a steep slope. It leaves behind rugged surfaces with a spectrum of reds, oranges and browns caused by the oxidation of the material’s iron. In a few places, the molten crust heaved up and snapped into pieces during tremors. This allows you to examine the successive lava flows like rings in a tree. The field’s average depth is about five feet.