The Olympic area is unique, for here the regional snowline descends to about 6,000 feet lower than anywhere within the boundaries of the Continental United States south of Alaska. Extraordinarily heavy annual snowfall and the high percentage of cloudy weather, which retards the melting of snow, combine to depress the snowline to such a low level. Glaciers of Glacier National Park Within the boundaries of Glacier National Park there are 50 to 60 glaciers, of which only two have surface areas of nearly one-half square mile, and not more than seven others exceed one-fourth square mile in area. All these bodies of ice lie at the heads of valleys with high steep headwalls on the east and north sides of high ridges at elevations between 6,000 and 9,000 feet, in all cases well below the snowline. Consequently, these glaciers owe their origin and existence almost entirely to wind-drifted snow. Ice within these glaciers moves slowly. The average rate in the smallest ones may be as low as 6 to 8 feet a year, and in the largest probably 25 to 30 feet a year. There is no period of the year when a glacier is motionless, although movement is somewhat slower in winter than in summer. Despite the slowness of its motion the ice, over a period of years, transports large quantities of rock material ultimately to the glacier’s end where it is piled up in the form of a moraine. [Illustration: FRONT OF SPERRY GLACIER] The largest glacier in the Park is Grinnell. In 1960 it had a surface area of 315 acres. Sperry is the second largest glacier in the Park. Its surface in 1960 was 287 acres. Both Grinnell and Sperry have probable maximum thicknesses of 400 to 500 feet. [Illustration: JACKSON GLACIER IS VISIBLE FROM GOING-TO-THE-SUN ROAD (BEATTY PHOTO)] Other important Park glaciers, although much smaller than the first two mentioned, are Harrison, Chaney, Sexton, Jackson, Blackfoot, Siyeh, and Ahern. Several others approach some of these in size, but because of isolated locations they are seldom seen. As a matter of fact, there are persons who visit Glacier National Park without seeing a single glacier, while others, although they actually see glaciers, leave the park without realizing they have seen them. This is because the highways afford only distant views of the glaciers, which from a distance appear much like mere accumulations of snow. A notable example is Grinnell as seen from the highway along the shore of Sherburne Lake and from the vicinity of the Many Glacier Entrance Station. The glacier, despite its length of almost a mile, appears merely as a conspicuous white patch high up on the Garden Wall at the head of the valley.