Rivers are bearing vast quantities of sediment and depositing these near their mouths, pushing out the coast line and filling in the bottom. The main mouths of the Mississippi are advancing into the Gulf, but at a comparatively slow rate. A break from the main river at Cubit's Gap just above the head of the passes, however, has done an enormous amount of land making, filling in an area of about 50 square miles between 1852 and 1905. [Illustration: FIG. 32. FISHING POINT, MARYLAND, FROM SURVEYS OF 1849 AND 1902, ILLUSTRATING BUILDING OUT OF A POINT ON THE COAST.] [Illustration: FIG. 33. GROWTH OF LAND AT CUBITS GAP, MISSISSIPPI DELTA, FROM 1852 to 1905.] [Illustration: FIG. 34. COLUMBIA RIVER ENTRANCE, SHOWING MOVEMENT OF SAND ISLAND, SURVEYS OF 1851, 1870 AND 1905.] The mouth of the Columbia River in Oregon shows an interesting example of the movement of an island. The chart of 1851 shows the center of Sand Island 3-1/4 miles southeast of Cape Disappointment, the chart of 1870 shows it 2-3/4 miles southeast, and the chart of 1905 shows it 1-1/4 miles easterly. This island has thus moved 2 miles northwesterly directly across the middle of the river entrance, closing up the former north channel. The southern point of the entrance, Clatsop Spit, has built out about the same distance. [Illustration: FIG. 35. CHANGES IN HAULOVER BREAK, NANTUCKET ISLAND, 1890 TO 1903.] [Illustration: FIG. 36. MAPS OF BOGOSLOF ISLAND, 1895 AND 1907, SHOWING CHANGES DUE TO VOLCANIC ACTION.] [Illustration: _Photo by U. S. R. C. Service._ FIG. 37. BOGOSLOF VOLCANO, BERING SEA.] Volcanic action in well authenticated cases has caused islands to rise or disappear. In the present location of Bogoslof Island in Bering Sea the early voyagers described a "sail rock." In this position in 1796 there arose a high island. In 1883 another island appeared near it. In 1906 a high cone arose between the two, and a continuous island was formed over 1-1/2 miles long and 500 feet high. The latest report (September, 1907) was that this central peak had suddenly collapsed and disappeared. Bogoslof is an active volcano, and the main changes have been the result of violent volcanic action. The history of this island for over a century past forms a remarkable record of violent transformations in the sea.