The highest and most spectacular volcano of the Tonga Islands, symmetrical Kao volcano rises steeply to 1030 m about 6 km north of Tofua Island. Kao is elongated in a NNE-SSW direction and, with the exception of a small flat area on the SSW coast, rises at angles exceeding 35 degrees to the summit, which has a series of small coalescing craters. The lower flanks of the basaltic-andesite volcano are densely jungled, but the upper slopes are almost vegetation free. No historical eruptions are known from Kao, and fresh-appearing lava flows are not seen, although the absence of sufficient time for erosion to produce deep gullies or high sea cliffs suggests a very recent origin.