1976 to the present. The average annual discharge is with a monthly maximum of in June, and a minimum of in February. The highest annual mean was in 1981, and the lowest was in 1978. At Telegraph Creek, the average annual discharge is . The lower Stikine near the international border is generally frozen from October/November to April/May, while at Telegraph Creek, freezing occurs about a week earlier and break-up occurs one to three weeks later. Geology The Stikine basin includes several major terranes or crustal fragments that accreted to the western North American continent starting from about 180 million years ago. The Stikine Plateau roughly corresponds with the northern part of the Stikine Terrane ("Stikinia"), part of the larger Intermontane Belt complex. The Cassiar and Omineca Mountains to the east are formed from granite batholith remnants of an ancient continental volcanic arc (the Omineca Arc) which arose as a result of subduction following Stikinia's collision with the North American continent. The Coast Mountains, to the west, are formed in the same manner by the later collision of the Insular Belt terrane with the Intermontane terrane. Subduction forces created the granite batholith of the Coast Range volcanic arc, which was eventually uplifted to form the contemporary Coast Mountains between the Stikine Plateau and the Pacific coast. Despite the Coast Mountains being higher in elevation than the interior plateaus and ranges, the Stikine flows west cutting through them to reach the Pacific. Several nearby rivers including the Copper, Alsek and Taku Rivers do the same, suggesting that these river systems had been established along the west coast of the North American continent prior to the development of the Coast Range Arc. During the uplift of the Coast Mountains, the rivers maintained their courses as antecedent streams. The ancestral Stikine River may be as much as 50 million years old, with the present uplift of the Coast Mountains starting about 7 million years ago. Beginning about 2.5 million years ago in the Pleistocene, much of the interior Stikine basin was covered by successive Ice Age glaciations. During interglacial periods, the continental ice sheet retreated northward but remnant Coast Mountain glaciers blocked the outlet of the Stikine River, causing glacier melt to back up the river valley and create Glacial Lake Stikine. The lake filled and emptied numerous times, leaving shoreline deposits high on nearby mountainsides. Glaciers and ice sheets still exist in