|
The Glacier Blanc is a glacier in the French département of Hautes-Alpes. Its name (which means "white glacier") derives from the fact that – unlike the nearby Glacier Noir ("black glacier") – its surface appears pristinely white due to an absence of morainic debris. A glacier that is largely free of such moraines is generally described in French as a ''glacier blanc''.〔See 〕 == Geography == The Glacier Blanc begins on the northern slopes of the most southwesterly of the four-thousanders in the Alps, the high Barre des Écrins. It is separated from the Glacier Noir to the south by the crest of ''Crête de l'Encoula'' (or ''Crête de l'Encula''), that runs from the Barre des Écrins to the ''Pointe du Serre Subeyran''. The upper part of the glacier is sometimes named ''Glacier de l'Enc(o)ula'' after this arête; on several older maps this name is used for the whole glacier.〔(Website of Kommune Pelvoux in Vallouise )〕 With its 5.9 km-long tongue (in 2002), the Glacier Blanc is the longest glacier in the Massif des Écrins and the largest in the southern French Alps. Its area of 5.34 km² (2002) is not, however, as great as that of the Glacier de la Girose and the Glacier du Mont-de-Lans, which form a common system.〔 The Glacier Blanc is a typical valley glacier, which initially runs in a curve towards the northeast below the Barre, before its tongue turns southeast, becoming an icefall. Its average incline is about 30%,〔 but it is flatter in its central section than on the north slope of the Barre des Écrins or in the icefall of its lower section. The glacier is bounded on its orographically left-hand side by, ''inter alia'', the summits of the Roche Faurio (), Pic de Neige Cordier () and the Montagne des Agneaux (). The ''Crête de l'Encoula'' forms the southern boundary, running from the Barre des Écrins over ''Barre Noir'' (), Pointe Mettrier () and Pointe de la Grande Sagne () to the Pointe du Serre Subeyran (). Between the peaks that surround the glacial basin are smaller side glaciers that feed the main stream. In its centre section the main stream (excluding side glaciers) of the Glacier Blanc is about 800 to 1000 metres wide. The greatest depth of ice occurs at the Refuge des Écrins where it is up to 250 metres deep; some 30 metres less than it was in 1985.〔 The glacier flows at a speed of around 40 metres per year in its central section (in the mid-1980s it moved at 50 m/yr) and at about 30 metres per year near its snout.〔〔〔The speeds quoted at :fr:Glacier Blanc and (Informationen zum Glacier Blanc von l'école de Magnières, l'Académie de Nancy-Metz ) of up to 350 metres per year are clearly too high.〕 Its reaction time, i.e. the time that elapses before the foot of the glacier advances or retreats due to major changes in conditions in the accumulation zone, is about 6 years in the case of the Glacier Blanc.〔 From its head at over high to its foot, currently (2010) at about (2002: 〔) the Glacier Blanc descends through a height of around 1,600 metres. The firn line on the Glacier Blanc, which separates the accumulation zone from the ablation zone, lies on the northern slopes at a height of about , and on the southern flanks at about .〔(Tim Stott, Professor of Physical Geography & Outdoor Education, Liverpool John Moores University )〕 The glacier's mass balance, an indicator of its health, has not been fully investigated.〔 The Glacier Blanc drains via the ''Torrent du Glacier Blanc'', the ''Gyr'', the Gyronde, the Durance and finally the Rhône into the Mediterranean Sea. 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「Glacier Blanc」の詳細全文を読む スポンサード リンク
|