GEOLOGY AND SOILS. Maine has had a very complex geological history. pre-Cambrian time the State was crossed by two great moun tain ranges. One extended along the northwest ern boundary through the White Mountains to Long Island Sound east of the Connecticut River; the other extended northeast, along the coast. These mountains were much folded, largely gneis sic and schistose, and they were worn down to base level in later Paleozoic time. Through the centre of the State, between these two ranges, a long gulf extended from Gaspe Peninsula to the southwest. By the end of Devonian time this trough was filled with sediments from the aging mountains, only to he uplifted. crumpled, and somewhat metamorphosed, again worn to base level and depressed, allowing carboniferous de posits to he laid down unconformably upon all the older beds. It was uplifted and again worn to base level in Cretaceous time, since which the region has been broadly lifted into a plateau of low elevation and again dissected. The Pleistocene ice sheet covered the State entirely, discharging its marginal ice into the sea. The effect' of glaciation was to denude the higher lands, accen tuate the river valleys, create many lake basins, and leave the surface strewn with a coating of till. Since Pleistocene time there has been a
considerable subsidence, resulting in the sub mergence of the coastal lowlands, and converting the higher hills and ridges into a fringe of isl ands, and the drowned valleys into fiords. The latest crustal movement has been a very slight uplift along the coast, uncovering small plains of marine clays which interlock with the rocky headlands. This same slight uplift has revived the rivers, furnishing very valuable water power at the bay heads.
The soils of Maine, with the exception of the Pleistocene marine clays along the coast, are almost wholly glacial. Along some of the rivers and lakes and in many old lake bottoms, long since filled up or drained out, there are alluvial plains of great fertility. The higher outcrops of the crystalline old land are largely denuded of all soil, while the whole surface of the State is more or leas strewn with glacial debris. The drift is in places arable, though in wide areas it is unsuited for agriculture. The character of the soil and the large supply and even distrihu tion of rainfall have been determining factors in making the State a rich forest region.