Upper Rhine Plain: Difference between revisions

[[Image:rhinegraben sat.jpg|thumb|275px|left|Satellite image showing the southern section of the Upper Rhine Plain and the rift flanks of Vosges, France, and the Black Forest, Germany.]]
[[Image:rhinegrabencross.jpg|thumb|275px250px|right|Schematic cross-section of the Rhine Rift Valley.]]
The Upper Rhine Plain was formed during the Early [[Cenozoic]] era, during the Late [[Eocene]] epoch. At this time, the [[Alpine Orogeny]], the major mountain building event that was to produce the [[Alps]], was in its early stages. The Alps were formed because the continents of Europe and Africa collided. It is thought that because the collision was '''irregular''', the initial contact between the two continents resulted in the formation of dilational (extensional) structures in the [[foreland basin]] to the north of the Alps.<ref>Sengor, A.M.C. 1976. "Collision of irregular continental margins: Implications for foreland deformation of Alpine-type orogens", ''Geology'', 4, 779-782.</ref> The result was substantial crustal thinning, forming a major extensional ''[[graben]]'' and causing isolated volcanic activity. The '''stretch factor''' is estimated to be ~2.
===Rift flank uplift===
[[Image:Vallee-chajoux.jpg|thumb|275px|right|The Vosges mountain range, France, formed by rift-flank uplift on the margins of the Rhine Graben.]] To both the east and west of the Rhine Plain, two major hill ranges have formed that run the length of the basin. To the west, in France, these hills are known as the [[Vosges mountain range]] and in the east, in Germany, the hills comprise the [[Black Forest]]. These ranges exhume the same types of rocks in their cores, including deep crustal [[gneiss]]. Both ranges correspond to uplifts of more than 2,500 metres, much of which has since been eroded. This uplift has occurred because of the isostatic response associated with the formation of an extensional basin. As a consequence, the highest mountains exist immediately adjacent to the margin of the basin, and become increasingly low outwards. The boundaries between the hill ranges and the Rhine Graben are defined by major, [[normal fault]] zones.
The northern section of the Rhine Graben is equally framed by somewhat lower mountain ranges, the [[Palatinate Forest]] on the western and the [[Odenwald]] on the eastern side.
[[File:Rhine rift.png|thumb|250px|right|Rhine Graben (blue shades) between Basel and Frankfurt with adjoining mountain ranges (green to brown); colour coding according to digital elevation model]]
==Volcanic activity==
The extension induced by the formation of the Alps was sufficient enough to thin the crust and provide suitable dilational conduits for magmatic and volcanic activity to occur. This resulted in the emplacement of [[mafic]] [[Dike (geology)|dykes]], which follow the general structural trend of the extensional faults. In addition, isolated volcanoes such as the Kaiserstuhl were formed.