A number of dikes[3] of Belt age, some of which undoubtedly were feeders to the sill and flows, cut vertically up through the sedimentary formations. Some of the dikes are less resistant to weathering and erosion than the rocks surrounding them; consequently their more rapid removal results in the formation of narrow vertical chimneys or recesses which appear as snow-filled chutes on the mountainsides in spring and early summer. Such a feature almost invariably indicates the presence of a dike. From Many Glacier Hotel one of these can be seen on the red mountain in front of Mount Wilbur. Another, 1,500 feet high, transects the Pinnacle Wall at the outlet of Iceberg Lake. The dike which forms this impressive chute is less than thirty feet wide. Though not so conspicuous as the sills some of these dikes are of interest because they contain various ore minerals, principally copper, which today form small deposits along their borders. About the beginning of the century these were responsible for a short-lived mining boom, the best known vestige of which is the remains of the mill at Cracker Lake. The old Cracker Mine, with entrance now caved in, was driven along a dike which has a width of over 100 feet. From the boat landing at the head of Josephine Lake the dump of another mine appears as a tiny gray-green mound on a narrow shelf high on the precipitous wall of Grinnell Point. Like the Cracker Mine this one was dug along the edge of a similar but smaller dike. All these deposits are insignificant in size and of no commercial value. Had they been important this great area might never have been set aside as a national park. [Illustration: MOUNT WILBUR AND THE PINNACLE WALL VIEWED FROM MANY GLACIER HOTEL. THE UPPER PART OF APPEKUNNY AND ALL OF THE GRINNELL AND SIYEH FORMATIONS ARE VISIBLE. THE SNOW-FILLED CHUTE LEFT OF THE WORD “GRINNELL” IS FORMED BY THE SAME DIKE WHICH PASSES THROUGH THE PINNACLE WALL. (HILEMAN PHOTO, COURTESY GLACIER PARK CO.)] The Story Continues For the succeeding several hundred million years the geologic history of Glacier National Park is rather obscure, but additional Belt sediments apparently were deposited before uplift of the area caused the sea to withdraw. Following this event many feet of the younger Belt sediments were removed by erosion. The sea probably returned and received more sediments during much of the Paleozoic Era, although no trace of these rocks has been found inside the park boundaries. CRETACEOUS ROCKS.