Several important areas of vineyards are grouped about the central lakes in western New York. While there are at least three distinct localities in this district, namely, the areas about the three lakes, Keuka, Canandaigua, and Seneca, yet the soils, climate, varieties and methods of caring for vineyards and product are so nearly alike that all may be treated as one district. The vineyards are in five counties, Ontario, Yates, Schuyler, Steuben and Seneca. The Keuka area, in Yates and Steuben Counties, is by far the largest; and the region is often called the Keuka grape district. Vineyards surround Keuka Lake and all but the northern end of Canandaigua Lake, but only on the banks of the southern half of Seneca Lake are grapes grown. The somewhat extensive vineyards about Naples, south of Canandaigua Lake; Bath, south of Keuka Lake; and of Romulus between Seneca and Cayuga Lakes, belong in the Central Lakes district. The geology of the Central or Finger Lakes has been studied by many workers and the geological history of these remarkable bodies of water is now well known.[105] It is very generally agreed that these lakes fill, in part, preglacial valleys and that the valleys were transformed into lakes by glacial action. The basins of the lakes may have been and probably were deepened by the erosive action of glaciers but it is fairly certain that there were pre-existing valleys which were dammed by glacial deposit. The topography is more or less rough and broken. The steep hillsides of the lakes were formed not only by erosion but by the tilting of the land. Beside these hillsides of the lakes to give character to the topography of the region, there are ranges of hills and the remains of some moraines, so that in general the land is very uneven. This is especially true of the parts of it devoted to grape-growing though in some grape sections there are many stretches of smooth and regular vineyards.