Foel Lwyd

The Carneddau (lit. "the cairns"; Carneddau is a Welsh plural form, and is sometimes anglicised to Carnedds) are a group of mountains in Snowdonia, Wales. They include the largest contiguous areas of high ground (over 2,500 or 3,000 feet (910 m) high) in Wales and England, as well as six or seven of the highest peaks in the country—the Fifteen Peaks. The range also encloses a number of lakes such as Llyn Cowlyd and Llyn Eigiau, and the Aber Falls waterfalls. It is delimited by the Irish Sea to the north, the Conwy valley to the east, and by the A5 road from Betws-y-Coed to Bethesda to the south and west. The area covers nearly 200 square kilometres, about 10% of the area of Snowdonia.

The rocks from which the Carneddau are formed mostly originated in the Ordovician period between 500 and 440 million years ago. At that time, the continental land masses on either side of the Iapetus Ocean were moving together. The friction between these caused the floor of the ocean to melt, volcanoes to form and the land to rise up. This was the origin of the towering mountains that were to become Snowdonia and the other mountain ranges in Central and North Wales. Over time, these mountains have been eroded by the weather and scoured by advancing and retreating ice sheets. The Carneddau were formed in this way and consist of volcanic and sedimentary rock. The last ice sheet retreated about 10,000 years ago. It left behind a landscape of smooth summits above erratic boulders and scree at the foot of cliffs on the eastern side of the mountains, and moraines that created shallow lakes in the cwms.

This area was first colonised in Neolithic times, when Stone Age farmers started clearing the native forests of oak and birch that covered all but the uppermost ridges and summits. They were followed by Bronze Age people who cleared more forests and erected standing stones across the uplands. There are more than one thousand ancient monuments on the Carneddau estate (the land owned by the National Trust, which covers the Carneddau and the Glyderau ranges). The remains of circular stone huts dating back to this time have been found and the cairns on the mountain summits contain cremated human remains, presumably from prominent people of this time.

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