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The Po Valley, Po Plain, Plain of the Po, or Padan Plain ((イタリア語:Pianura Padana) (:pjaˈnuːra paˈdaːna) or ''Val Padana'') is a major geographical feature of Italy. It extends approximately in an east-west direction, with an area of including its Venetic extension not actually related to the Po River basin; it runs from the Western Alps to the Adriatic Sea. The flatlands of Veneto and Friuli are often considered apart since they do not drain into the Po, but they effectively combine into an unbroken plain. The plain is the surface of an in-filled system of ancient canyons (the "Apennine Foredeep") extending from the Apennines in the south to the Alps in the north, including the northern Adriatic. In addition to the Po and its affluents the contemporary surface may be considered to include the Savio, Lamone and Reno to the south, and the Adige, Brenta, Piave and Tagliamento of the Venetian Plain to the north, among the many streams that empty into the north Adriatic from the west and north. Geo-political definitions of the valley depend on the defining authority. The Po Basin Water Board (''(イタリア語:Autorità di bacino del fiume Po)''), authorized in 1989 by Law no. 183/89 to oversee "protection of lands, water rehabilitation, the use and management of hydro resources for the rational economic and social development, and protection of related environment" within the Po basin, has authority in several administrative regions of north Italy, including the plain north of the Adriatic and the territory south of the lower Po, as shown in the regional depiction included with this article. The law defines the Po basin as "the territory from which rainwater or snow and glacier melt flows on the surface, gathers in streams of water either directly or via tributaries...".〔(【引用サイトリンク】publisher=CABRI-Volga )〕 The United Nations Environment Program includes the Alps and Apennines as far as the sources of the tributaries of the Po but excludes Veneto and that portion of Emilia-Romagna south of the lower Po; that is, it includes the region drained by the Po but only the Po and its tributaries.〔(【引用サイトリンク】publisher=United Nations Environment Programme, Division of Early Warning and Assessment (DEWA), Global Resource Information Database (GRID) - Europe )〕 The altitude of the valley through which the Po flows exclusive of its tributaries varies from approximately below sea level in the Polesine subregion (the delta around Ferrara)〔(【引用サイトリンク】publisher=Consorzio di Bonifica II Circondario - Polesine di San Giorgio )〕 to about at the river's origin in the southern Piedmontese province of Cuneo, also known as the ''Provincia granda''. The valley is crossed by a number of affluents running down from the Alps in the north and from the Apennines in the south. The Po's major affluents include the Tanaro, Scrivia, Trebbia, Panaro and Secchia in the south, Dora Riparia, Dora Baltea, Sesia, Ticino (draining Lake Maggiore), Lambro, Adda (draining Lake Como), Oglio (draining Lake Iseo) and Mincio (draining Lake Garda and called Sarca in its upper reaches) in the north. ==Geology== The Po Valley and the Adriatic overlay a foreland basin and a system of deeply buried ancient canyons surviving from the tectonic collision of an offshore land mass, Tyrrhenis, with the mainland, an incident within the collision of the African and Eurasian plates. Since the Messinian (7-5 mya) the system has been filling with sediment mainly from the older Apennines but also from the Alps. The shoreline of the Adriatic depends on a balance between the sedimentation rate and isostatic factors. Until about 1950 the Po delta was prograding into the Adriatic. After that time due to human alteration of geologic factors, such as the sedimentation rate, the delta has been degrading and the coastline subsiding, resulting in ongoing contemporaneous crises in the city of Venice, where much irreplaceable art and architecture is likely to be lost due to soaring sea level in the next centuries. Where the land surface now dips below sea level the river must run at a relative elevation between dikes. The Malossa gas condensate field was discovered in 1973 and produces at depths of 6 km from the Upper Triassic Dolomia Principale dolomite and the Lower Jurassic Zandobbio dolomite, capped by the Lower Cretaceous Marne di Bruntino marl.〔Errico, G., Groppi, G., Savelli, S., and Vaghi, G.C., 1980, Malossa Field: A deep Discovery in the Po Valley, Italy, in Giant Oil and Gas Fields of the decade: 1968-1978, AAPG Memoir 30, Halbouty, M.T., editor, Tulsa: American Association of Petroleum Geologists, ISBN 0891813063, pp. 525-538〕 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「Po Valley」の詳細全文を読む スポンサード リンク
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