Photos of Charles Darwin National Park

Cwm Idwal (2) by Darkroom Daze

<b>View south into Cwm Idwal showing the wall of the Cwm, with Twll Du (Devil's Kitchen) - the dark wide vertical gash below the lowest point on the skyline.</b> General views of the wall of the Cwm (= corrie or cirque) are difficult to photograph because the cliffs face North and are therefore mostly in shadow - I actually took this shot in bright sunny weather, but I had to do quite a bit of digital editing to bring out the geological details of the cliffs, hence the somewhat unreal colours. There is also not much in the picture to indicate the scale, but the cliffs proper are about 300-450 ft (100-150m) high. See notes on picture for details of the view, including some of the geology. ---------- <b>IN DARWIN'S FOOTSTEPS</b> DARWIN'S 'WELSH EXPEDITION' TO THE 'NORTH-WEST MOUNTAINS': AUGUST 5-18, 1831: LLANGOLLEN TO BARMOUTH (ABERMAW) <i>Darwin did this field trip just a few months before he sailed on HMS <u>Beagle</u>. The field trip was instigated by his then geology professor at Cambridge, Adam Sedgwick, whom Darwin accompanied as a student assistant for some of Sedgwick's longer trip. Darwin also did some the expedition separately from Sedgwick. Much of the geology of North Wales is challenging and there were few previous studies. Although it was a relatively short trip, Darwin later acknowledged that it significantly helped him to develop his geological knowledge and field skills, as well as his enthusiasm for geology generally. It therefore laid important foundations for his <u>Beagle</u> voyage. (It is not always realized that in the years before he published his best known work (<u>Origin of Species</u>, 1859), Darwin regarded himself primarily as a geologist, and was recognized as such by his contemporaries during those years.) Darwin did not record the exact dates and route of much of this trip, but Michael Roberts (source below) has drawn on various sources to make a plausible reconstruction, which I have used to caption these 'footsteps' photos. </i> Historically, Cwm Idwal is one of the most important places Darwin visited in Britain. He first visited it on his own on August 14th 1831 while Sedgwick was returning from his side-trip to Ireland. Darwin was on his way from Penrhyn slate quarries near the coast, to Capel Curig, folllowing what is now the route of the main trunk road through northern Snowdonia, the A5. He later revisited Cwm Idwal with Sedgwick in 1842, after Darwin had returned from his <i>Beagle</i> voyage (1831-1836). In his later visit, he was concerned with the glacial features, but in his notes on his earlier visit, he had concentrated on the bed-rocks, as follows. [p.13] <b><i>&quot;Cwlm Idwal consists in a circle of steep rocks surrounding the Llyn</i></b> [= lake (Llyn Idwal) out of view here]<b><i>. they generally consist of an altered slate, which is very tough, of a light green colour, sometime passing into a very compact conglomerate, occasionally having an amydaloid appearance: the parts which are weathered, become converted into a very rotten slate. The general cleavage is E by N &amp; S by W dipping to the W 2 N.70 Many of the planes of cleavage are covered with quartz containing fibres of Titanium. This rock in many parts has a tendency to split into prismatic forms, &amp; chinks under the hammer. in general appearance it resembles a basalt. But what is very important it contains organic remains, both in the hard light green &amp; the conglomerate. I found Madrepores </i></b>[p.14] <b><i>to the South of the lake. there is a very large mass of Basalt protruded out of the Slate. In shape it must be an inverted cone. as a section has the appearance of lapping over the slate. The Junction on each side is most clear. The basalt is a compact rather brittle, black rock, splitting with conchoidal fracture. The whole mass is more or less divided into 4, 5, or 6 sided pillars, &amp; each pillar appears to be jointed, about a foot apart. A natural surface where the pillars end appears like tesselated pavement. The basalt appears to have carried with a large bed of the altered slate. At the entrance to Llyn Idwal is a quarry for Hone slates.&quot;</i></b> Darwin sketched the cliffs, showing the cliffs consisting of a basalt lava flow at the top, in the form of a shallow inverted cone, with a feeder vent at Twll Du, in the &quot;slates&quot; below (see notes on picture). His idea of the vent here was perhaps influenced by his earlier geological experience of Arthur's Seat in Edinburgh, though vents do occur elsewhere in this same area of Snowdonia. In fact, there is no vent here, and the cone-like structure is not a cone, nor a primary structure, but a down-fold (syncline) affecting all of the rocks here. The &quot;inverted cone&quot; was presumably some kind of volcanic crater in Darwin's mind. SOURCES - Darwin, C.R., 1831. <a href="http://darwin-online.org.uk/content/record?itemID=CUL-DAR5.B5-B16" rel="nofollow">darwin-online.org.uk/content/record?itemID=CUL-DAR5.B5-B16</a> - Barrett, Paul H. 1974. The Sedgwick-Darwin geologic tour of North Wales. <i>Proceedings of the American Philosophical Society</i> 118, No. 2. (19 April), pp. 146-164.<a href="http://darwin-online.org.uk/content/frameset?viewtype=text&amp;itemID=F1964&amp;pageseq=1" rel="nofollow">darwin-online.org.uk/content/frameset?viewtype=text&amp;i...</a> - Gannon, P., 2008. <i>Rock trails. Snowdonia. A hillwaker's guide to the geology &amp; scenery.</i> Pesda Press, Caernarfon. - Roberts, Michael B., 1996. Darwin at Llanymynech: the evolution of a geologist. <i>British Journal for the History of Science</i> v. 29, p. 469-478. - Roberts, Michael B., 1998. Darwin's dog-leg: the last stage of Darwin's Welsh field trip of 1831. <i>Archives of Natural History</i> v. 25, p. 59-73. ---------- <b>GEOLOGICAL NOTES</b> The cliffs consist of Ordovician (Caradocian) sediments, basalt, and felsic pyroclastics (volcanic ash deposits), folded into a shallow syncline, indicated here by the complementary dip of the rocks inwards towards Twll Du. A basalt flow occupies the central uppermost cliffs, and most of the rest of the cliffs are in the Lower Rhyolitic Tuff, interpreted as part of a large former volcanic caldera. The landscape of the Cwm is glaciated, the cliffs forming the back of the cwm (aka cirque, corrie). ---------- <b>Photo</b> Darkroom Daze © <a href="http://bit.ly/47tbGf" rel="nofollow">Creative Commons</a>. If you would like to use or refer to this image, please attribute. ID: CIMG1698_2
Charles Darwin National Park is a tourist attraction, one of the National parks in Darwin, Australia. It is located: 38 km from Palmerston. Read further
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