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See also:CIRQUE (See also:Lat. See also:circus, See also:ring) , a See also:French word used in See also:physical See also:geography to denote a semicircular See also:crater-like See also:amphitheatre at the See also:head of a valley, or in the See also:side of a glaciated See also:mountain. The valley cirque is characteristic of calcareous districts. In the Chiltern Hills especially, and generally along the See also:chalk escarpments, a See also:flat-bottomed valley with an intermittent stream winds into the See also:- HILL
- HILL (0. Eng. hyll; cf. Low Ger. hull, Mid. Dutch hul, allied to Lat. celsus, high, collis, hill, &c.)
- HILL, A
- HILL, AARON (1685-175o)
- HILL, AMBROSE POWELL
- HILL, DANIEL HARVEY (1821-1889)
- HILL, DAVID BENNETT (1843–1910)
- HILL, GEORGE BIRKBECK NORMAN (1835-1903)
- HILL, JAMES J
- HILL, JOHN (c. 1716-1775)
- HILL, MATTHEW DAVENPORT (1792-1872)
- HILL, OCTAVIA (1838– )
- HILL, ROWLAND (1744–1833)
- HILL, SIR ROWLAND (1795-1879)
hill and ends suddenly in a cirque. There is an excellent example at Ivinghoe, See also:Buckinghamshire, where it appears as though an enormous flat-bottomed See also:scoop had been driven into the hillside and dragged outwards to the See also:plain. In all cases it is found that the valley See also:floor consists of hard or
See also:CISSEY
impervious See also:rock above which lies a permeable or soluble stratum of considerable thickness. In the See also:case of the chalk hills the upper strata are very porous, and the descending See also:water with atmospheric and humous acids in See also:solution has See also:great solvent See also:power. During the See also:winter this upper layer becomes saturated and some of the water drains away along See also:joints in the escarpment. An underground stream is thus See also:developed carrying away a great See also:deal of material in solution, and in consequence the ground above slowly collapses over the stream, while the cirque at the head, where the stream issues, gradually See also:works backward and may pass completely through the hills, leaving a See also:gap of which another drainage See also:system may take See also:possession. In the See also:limestone See also:country of the Cotteswold Hills, many small intermittent tributary streams are headed by cirques, and some of the longer dry valleys have springs issuing from beneath their See also:lower ends, the dry valleys being collapsed areas above underground streams not yet revealed. In this case the pervious limestone is underlain by beds of impervious See also:clay. There are many of these in the See also:Jura Mountains. The Cirque de St Sulpice is a See also:fine example where the impervious See also:bed is a marly clay. '
The origin of the glacial cirque is entirely different and is said by W. D. See also:- JOHNSON, ANDREW
- JOHNSON, ANDREW (1808–1875)
- JOHNSON, BENJAMIN (c. 1665-1742)
- JOHNSON, EASTMAN (1824–1906)
- JOHNSON, REVERDY (1796–1876)
- JOHNSON, RICHARD (1573–1659 ?)
- JOHNSON, RICHARD MENTOR (1781–1850)
- JOHNSON, SAMUEL (1709-1784)
- JOHNSON, SIR THOMAS (1664-1729)
- JOHNSON, SIR WILLIAM (1715–1774)
- JOHNSON, THOMAS
Johnson (See also:Journal of See also:Geology, xii. No. 7, 1904) to be due to basal sapping and erosion under the See also:bergschrund of the See also:glacier. In this he is supported by G. K. See also:- GILBERT
- GILBERT (KINGSMILL) ISLANDS
- GILBERT (or GYLBERDE), WILLIAM (1544-1603)
- GILBERT, ALFRED (1854– )
- GILBERT, ANN (1821-1904)
- GILBERT, GROVE KARL (1843– )
- GILBERT, J
- GILBERT, JOHN (1810-1889)
- GILBERT, MARIE DOLORES ELIZA ROSANNA [" LOLA MONTEZ "] (1818-1861)
- GILBERT, NICOLAS JOSEPH LAURENT (1751–1780)
- GILBERT, SIR HUMPHREY (c. 1539-1583)
- GILBERT, SIR JOSEPH HENRY (1817-1901)
- GILBERT, SIR WILLIAM SCHWENK (1836– )
Gilbert in the same journal, who produces some remarkable examples from the Sierra See also:Nevada in See also:California, where the mountain fragments have been See also:left behind " like a See also:sheet of dough upon a See also:board after the See also:biscuit See also:tin has done its See also:work "; se that above the head of the glaciers " the rock detail is rugged and splintered but its See also:general effect is that of a great symmetrical arc." Descending one of the bergschrunds of Mt. See also:Lyell to a See also:depth of 150 ft., Johnson found a rock floor cumbered with See also:ice and blocks of rock and the rock See also:face a literally See also:vertical cliff " much riven, its fracture planes outlining See also:sharp angular masses in all stages of displacement and dislodgment." Judging from these facts, he interprets the deep valleys with cirques at their head in formerly glaciated regions where at the head there is a " reversed grade " of slope, as due to ice-erosion at valley-heads where scour is impossible at the sides of the mountain but strongest under the glacier head where the ice is deepest. The opponents of ice-erosion nevertheless recognize the very frequent occurrence of glacial cirques often containing small lakes such as that under Cader Idris in See also:Wales, or at the head of Little See also:Timber See also:Creek, See also:Montana, and numerous examples in Alpine districts.
End of Article: CIRQUE (Lat. circus, ring)
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