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The Archipelago of Lake Saint-Pierre〔Official name since 1985 - (Commission de toponymie du Québec (Geographical Names Board of Québec) )〕 counts 103 islands in the western part of Lake Saint-Pierre, in Quebec, in Canada. There are two groups: Islands of Berthier to the north and the islands of Sorel to the south. The shores of this archipelago has twenty-two coastal villages. Around 2600 people were living on those islands in 2011.〔Lorraine Guay, Quebec islands, collection: the Regions of Quebec, Brief History, Laval University Press, 2011〕 Islands Dupas and Saint-Ignace-de-Loyola are partially urbanized. The majority of the other islands are used for agriculture and grazing farm animals. A network of small roads, often unpaved crosses the riparian environment of the islands. The islands of Saint-Ignace-de-Loyola, Dupas and Castors (Beavers) are connected to the north side of St. Lawrence River by a small network of bridges. The connection between the two sides of St. Lawrence River) is provided by a ferry service between Sorel and Saint-Ignace Island (the largest island of the archipelago). Most of the other islands are accessible only by boat. The south side of the river, the "Île des Embarras" (Embarrassment Island) is the smallest of the inhabited islands. == Geology == The Archipelago of Lake Saint-Pierre is a delta from the last glaciation and modified by the alluvium of St. Lawrence River.〔It is a channel flowing into a plain of sand and clay.〕 Following the withdrawal of the ice cap, the Sorel Islands region was invaded by the Champlain Sea which is then withdrawn gradually, about 12000 years ago. Clayey marine sediments were deposited at the bottom of the water.〔This Mateau clay reached in 2011 several water depths; so it is about 167 meters deep to Berthierville〕 The visible part of the islands of the Archipelago is formed of recent alluvium. These deposits with a maximum height of 7 to 8 meters above the river level consist mainly of silt deposited by the Champlain Sea at the back that forced marine waters this time to integrate the current riverbed. Today, the same phenomenon is repeated annually during spring flooding〔These spring floods have led islanders to build buildings and houses on stilts. Even today, gathering maple sap during sugaring is done by boat to the islands.〕 while the waters of the river cover a portion of the Sorel Islands and will leave a layer alluvium. Although they can cause problems and damage to the island for a few weeks to travel, the spring floods are beneficial to agriculture.〔The alluvial deposits left after the removal of spring flooding is an important contribution of beneficial organic matter to grain production Islands.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Archipelago of Saint-Pierre Lake」の詳細全文を読む スポンサード リンク
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