Crater Lake National Park, Oregon

9. Wizard Island

Wizard Island consists of a black, broken, and irregular mass of rock. This is an andesite lava which has flowed out of the volcanic cone which is Wizard Island. It apparently did not come from the summit of the cone, but came out of its side at or near the level of the lake. It is possible that the Lake was present at the time and the lava may have flowed into the water, but the absence of vertical pillow structure would seem to indicate that the Lake had not yet formed. At any rate it cooled rapidly. It is evident that the cooling was much more rapid on the surface, since it seems that the jumbled mass over which the island explorer must climb is the broken surface of a flow which continued to move after its surface had frozen enough to be fractured by sub-surface movement. The flow was quite irregular as to directional movement because the shore of the island is irregular, forming numerous bays and inlets. The lava is often of a vesicular or porous nature. It is also quite hilly and rugged.