There is less vegetation in the valley—which comprises much of the national park—than to the north and east of the mountain because the valley lies in a rain shadow.Prevailing winds drop rain on the eastern and northern sides of the mountains because moisture gets squeezed from the air as it flows up and over the slopes.The valley was sculpted by the forces of erosion rather than by the explosive eruptions that produce volcanic craters or the sinking of land (after eruptions) that creates calderas.
“This floor, broken by lava flows, and cinder cones, was as red and fresh and uneroded as if were but yesterday that the fires went out,” London noted.
“The cinder-cones, the smallest over four-hundred feet in height and the largest over nine-hundred, seemed no more than puny little sand hills, so mighty was the magnitude of the setting.” On February 6, 2015, the Operational Land Imager (OLI) on Landsat 8 acquired this image of eastern Maui.
Haleakalā National Park was created on August 1, 1916, as part of Hawaii National Park.
At that time, the park also included Kilauea and Mauna Loa.
Dating of tree-rings shows that this ratio has fluctuated through time.