Upward of 200 islands belong to Michigan. The largest. are Isle Royale and Grande Isle in Lake Sultrier: Sugar Island, Encampment Island, Drummond Island, Bois Blanc, Mackin:1e, arid Alarquette at the head of Lake lluron: and the Beaver, Fox, and Manit011 groups at the head of Lake Michigan. The chief indentations of the coast of the Lower Peninsula are Grand and Little Traverse bays on the northwest, and Thunder and Saginaw bays on the east side. to the northern peninsula are Koweenaw Bay east of Keweenaw Peninsula. and White Fish Bay on the northern shore at tin west end of Saint Mary's Eiver. On the south are the Big Bay and the Little Bay of Noqiiet at of Green Bay. One of the interesting features of the NIiebigan coast is the 'Pictured leeks' on the northern coast of the northern peninsula. where the Cambrian sandstones are carved by the action of the water into fantastic shapes—a relies, towers, castles, eh% In some place.; Nteallier, earl pass directly under the rocks and behind falling cascades.
Cr ttrATE. Though )lielligan lies in the heart of the north temperate zone. the northern penin sula has a rigorous climate. only in the south ern tier of counties are the plant. and animal species wholly mistral. The average track of the extratropieal cyclonic storms for all the continent crosses the State, flyer -150 such dis turbances passed that way in ten years. The aver age temperatures for .fuly are 05° F. for Bes ,einer and Mackin:1e. and 70° F. for Detroit. The southwestern side of the Upper Peninsula and the southeastern corner of the Lower Peninsula have a loaND1111111 temperature of Inn°. win ter minimum is 20° below zero for Detroit, and 30° below at 1:eweenaw Point. This gives a range of 130° for the Upper Peninsula and of 120° for the Lower. Sault Sainte holds the 'United States record for the frequency of cold waves, with a fall of F. or over in twenty four hours. The average rainfall for the State is 30 inches. The northern peninsula from Keweenaw Point to Sault Sainte Marie holds the record in the United States for the heaviest annual snowfall, 130 inches. This is reduced to only 40 inches at Ann Arbor. Presque Isle County has precipitation, on the average. 170 days in the year, sharing with Buffalo the high est record in the United States east of Cape Flattery. The prevailing winds for January and July alike are southwest for the Lower Peninsula and northwest for the Upper. There are on the average twenty thunderstorms per year, with a maximum frequency in .111ly.
For Fr.on_c and FAI.NA, see these sections under UNITED STATES.
GEoLony. The State of Michigan in its Upper and Lower peninsulas has all the recognized series of rocks from _\relnean to Carboniferous inclusive. The earlier part of this record is
represented in great detail in the rocks of the northern peninsula. In fact, the region around Lake Superior, including northern portions of Minnesota, Wisconsin. and has had an extremely involved geological history, the care ful and detailed study of which, by a host of geologists. has added more largely to our knowl edge of pre-Cambrian geology than any equiva lent area. in the world. This study has disclosed a. whole system (Alg.onkian) of rocks below the Paleozoic, representing perhaps a longer lapse of ages than all the time since the beginning of tire Cambrian. The earliest beds of the Alponkinn are much metamorphosed and cut in every direc tion by dikes and sills of igneous intrusives and extrusives. The Penokee-Gogebie and the Mar quette-Menominee members of this system are the great iron-hearing beds of the northern penin sula. They dip down under the bed of Lake Superior and outcrop again in the Vermilion and Mesabi ranges in Minnesota. .\t the top of the Algonkian are the copper-bearing beds. The copper is found usually in elastie beds, largely in conglomerates. though sometime, in sandstone and adjaeent lava sheets.
Lower Peninsula of Michigan is essentially a bowl-shaped depression in the pre-Cambrian erust, between the old ArcInean island of North Wisconsin and the similar island of the Adiron (lacks. This grand synclinal trough was being tilled with sediments through Cambrian. Ordo vician, Silurian. Devonian, and Carboniferous ages, the successive deposits lying like a pile of saucers. with outcropping edges all dipping to ward the centre. In Suit-Carboniferous time the basin was a narrow-mouthed hay, acting as a salt pan, concentrating sea-water and depositing beds of rock salt. In upper Carboniferous some beds of coal were laid down. The Stale has evidently been continuously above the sea since Cariamiferous time. The present surface of 111e Mate is largely determined by glacial action. beimg very much smoothed over. and eovered with a sheet of till, in some places some hundreds of feet in thiekness. The present rivers arc consequent upon the drift surface, and many smaller lakes have a glacial The soil on the whole is extremely fertile. lasing 11111(1(4 up of the glacial detritus of lime stones, with large contributions from the older rocks of Canada. In the uurthern portions, where the outempping rock was a Paleozoic• sandstone, the soil is light and worthless and lit only for pine and other trees.