Kau Desert
The Kaʻū Desert is a leeward desert in the district of Kaʻū, the southernmost district on the Big Island of Hawaii, and is made up mostly of dried lava remnants, volcanic ash, sand and gravel. The desert covers an area of the Kīlauea Volcano along the Southwest rift zone. The area lacks any vegetation, mainly due to acid rainfall.
Kaʻū desert is not a true desert in that rainfall exceeds 1,000 millimeters (39 in) per year. However, rain combines with sulfur dioxide, released by volcanic vents, and forms acid rain. The pH of the rain, as low as 3.4 during an eruption, inhibits plant growth. Furthermore, water evaporates quickly on the ground and the tephra soil is extremely permeable.
The Kaʻū Desert is popular for walking and hiking tours during inactive periods. It can be reached by following Highway 11 counterclockwise from Kona to the volcano. The trailhead is on Crater Rim Drive, coordinates 19°24′31″N 155°17′48″W / 19.40861°N 155.29667°WCoordinates: 19°24′31″N 155°17′48″W / 19.40861°N 155.29667°W. By traversing the desert, one can cross the Great Crack and the Southwest Rift Zone, a major fault zone that looks like a giant groove in the earth, before reaching Kīlauea Volcano. From the city of Hilo, take Highway 11 about 30 miles (48 km) west. The area is part of Hawaii Volcanoes National Park, but often is closed during periods of high volcanic activity, due to the potential for poisonous gas blown southwest by the tradewinds from the Halemaʻumaʻu vent.
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