The southwestern part of the range is drained by the upper French Broad River which, like the Nolichucky, is west of the Eastern Continental Divide and thus its waters eventually wind up in the Gulf of Mexico. The southern face of the hook drains into Flat Creek and the north fork of the Swannanoa River which also heads to the French Broad River. The North Fork Reservoir, supplied with the ample rain caused by moisture pushing up the southern face, serves as the primary water source for the Asheville region. A few of the streams in the southeastern section of the range are part of the Catawba River watershed, and are thus east of the Eastern Continental Divide. Notable summits While the crest of the Black Mountain range is just long, within these fifteen miles are 18 peaks climbing to at least above sea level. The Black Mountains rise prominently above the surrounding lower terrain. This is particularly noticeable from the range's eastern side, which rises over above the Catawba River Valley and Interstate 40, providing some impressive mountain scenery. Geology The Black Mountains consist primarily of Precambrian gneiss and schists formed over a billion years ago from primordial sea sediments. The mountains themselves were formed roughly 200–400 million years ago during the Alleghenian orogeny, when the collision of two continental plates thrust what is now the Appalachian Mountains upward to form a large plateau. Weathering and minor geologic events in subsequent periods carved out the mountains. During the last ice age, approximately 20,000–16,000 years ago, glaciers did not advance into Southern Appalachia, but the change in temperatures drastically changed the forests in the region. A tree-less tundra likely existed in the Black Mountains and surrounding mountains in elevations above . Spruce-fir forests dominated the lower elevations during this period, while hardwoods "fled" to warmer refuges in the coastal plains. As the ice sheets began retreating 16,000 years ago and temperatures started to rise, the hardwoods returned to the river valleys and lower slopes, and the spruce-fir forest retreated to the higher elevations. Today, the spruce-fir forest atop the Black Mountains is one of ten or so spruce-fir "islands" remaining in the mountains of Southern Appalachia. Plants and wildlife The forests of the Black Mountains are typically divided into three zones based on altitude: the spruce-fir forest, the northern hardwoods, and the Appalachian hardwoods. The southern Appalachian spruce-fir forest, though