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Santa Cruz River (Argentina)

Santa Cruz River is a river from the Argentine province of Santa Cruz.

The Santa Cruz begins at the shore of the Viedma and Argentino Lakes, of glacial origin and located in the Los Glaciares National Park, and runs 385 km eastwards before reaching the Atlantic Coast, 350 miles north of the southern tip of South America, creating a delta.

The river has an important flow of 790 m3 on average, and is used not only for irrigation but also for hydroelectricity production.


On April 13, 1834, the Beagle anchored in the mouth of the river to begin an expedition up the river as part of its survey voyage. Three boats set out on April 18, carrying twenty-five men, including Captain Robert Fitz Roy and naturalist Charles Darwin. All involved took turn in teams dragging the boats up river for 16 days. Darwin took careful note of everything, including the terrain around the river the flora and fauna of the region, and the geology exposed as the river cut through the plains.

April 22nd. -- The country remained the same, and was extremely uninteresting. The complete similarity of the productions throughout Patagonia is one of its most striking characters. The level plains of arid shingle support the same stunted and dwarf plants; and in the valleys the same thorn-bearing bushes grow. Everywhere we see the same birds and insects. Even the very banks of the river and of the clear streamlets which entered it, were scarcely enlivened by a brighter tint of green. The curse of sterility is on the land, and the water flowing over a bed of pebbles partakes of the same curse. Hence the number of waterfowl is very scanty; for there is nothing to support life in the stream of this barren river. [*]

Captain Robert Fitz Roy had previously given Darwin a book by Charles Lyell on Principles of Geology which used the paradym that the key to the past is the present and that led to the interpretation of present geology in the light of slow and gradual processes. Being convinced such a valley could only be cut by seas over long ages and such a valley should cut through the continent connecting Atlantic and Pacific, Darwin prevailed upon the HMS Beagle to have an expedition down the Santa Cruz river for 100 miles.


In his Journal of researches, p. 218, Darwin criticised former geologists who, in trying to explain the erosion of the lava and other rocks of the valley,

"....would have brought into play, the violent action of some overwhelming debacle; but in [the case of the Santa Cruz] such a supposition would have been quite inadmissible; because the same step-like terraces, that front the Patagonian coast, sweep up on each side of the valley. No possible action of any flood could have thus modelled the land in these two situations; and by the formation of such terraces the valley itself has been hollowed out....we must confess it makes the head almost giddy to reflect on the number of years, century after century, which the tides unaided by a heavy surf, must have required to have corroded so vast an area and thickness of solid rock."

He was wrong. The expedition ended due to fast water and turned around, had they gone a bit further they would have discovered the true cause of the river valley to be a glacial lake at the foot of the mountain. This he would never discover [*] and clung to the conclusions demanded by his presupposisions.

May 4th. -- Captain Fitz Roy determined to take the boat no higher. The river had a winding course, and was ver rapid; and the appearance of the country offered no temptation to proceed any further. Everywhere we met with th same productions, and the same dreary landscape. We wer now one hundred and forty miles distant from the Atlantic and about sixty from the nearest arm of the Pacific. Th valley in this upper part expanded into a wide basin, bounde on the north and south by the basaltic platforms, and fronte by the long range of the snow-clad Cordillera. But w viewed these grand mountains with regret, for we wer obliged to imagine their nature and productions, instead o standing, as we had hoped, on their summits. Besides th useless loss of time which an attempt to ascend the river an higher would have cost us, we had already been for som days on half allowance of bread. This, although reall enough for reasonable men, was, after a hard day's march rather scanty food: a light stomach and an easy digestio are good things to talk about, but very unpleasant in practice

5th. -- Before sunrise we commenced our descent. W shot down the stream with great rapidity, generally at th rate of ten knots an hour. In this one day we effected wha had cost us five-and-a-half hard days' labour in ascending On the 8th, we reached the Beagle after our twenty-one days expedition. Every one, excepting myself, had cause to b dissatisfied; but to me the ascent afforded a most interestin section of the great tertiary formation of Patagonia

Darwin is said to have come within 30 minutes of the mountains in the following reference. [*] The river valley cut through 300 feet of basalt was cut by a catastrophic glacial lake overflow and not by slow and gradual processes. One wonders how Darwin's thinking may have been different had his ship reached the glacial lake and the geology paradyms of Lyell seen as not always reliable, a paradym Darwin would extrapolate from the realms of geology to biology. The Santa Cruz river valley is one of many valleys once thought to have been cut slowly over millions of years but today recognized to have been made quickly by catastrophic glacial flooding. Catastrophic deglaciation flooding has also been suggested related to glacial Lake Missoula in the Northeastern United States and although initially ridiculed is now accepted as the prevailing view.

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