The Mystery of the Missing Medieval Sea

The mystery of the missing sea is one that has personally intrigued me recently. Through all of the Welsh history I have covered on this channel, I have never encountered a phenomenon as mysterious as what I've dubbed as the "islands that aren't islands". Throughout a small valley in Wales, near the towns of Porthmadog and Tremadog, there are 10 hills that aren't called hills at all, but "islands", despite being completely away from the ocean, a phenomenon that is completely unique throughout the history of Wales. Wales' history is full of mysteries, and these islands that aren't islands, surrounded by a missing medieval sea, is another one of them. Chapters: 0:00 - Islands that Aren't Islands 0:45 - Ynys, Ynys, Ynys 2:52 - Traeth Mawr 5:10 - How to Remove 13 Miles of Coastline (100% Effective!) 7:35 - William Madocks Sources (turn on captions): Hislop, M. (2024). A Guide to the Medieval Castles of England. Pen & Sword History, [1] pp. 175, [2] 176. Llyfrgell Genedlaethol Cymru / National Library of Wales. Cambriae Typus. [3] https://www.library.wales/discover-learn/digital-exhibitions/maps/maps-of-wales/cambriae-typus. Rhind, P.M. and Jones, A. (1994). Brackish saltmarsh communities in the Glaslyn marsh trust reserve. Field Studies, 8, [4] p. 373. Robinson, G. and King, T.J. (2019). At Home on the Waves: Human Habitation of the Sea from the Mesolithic to Today. Berghahn Books, [5] pp. 145-146, [6] 146, [7] 146-148, [8] 147. Thomas, D., (1959). MADOCKS, WILLIAM ALEXANDER (1773 - 1828), industrialist and philanthropist. Dictionary of Welsh Biography. [9] https://biography.wales/article/s-MADO-ALE-1774 Tweet by @KeithAPettit: [10] https://twitter.com/KeithAPettit/status/1742951095784071278 -------------------- Maps: © OpenStreetMap contributors, licensed under CC BY-SA: https://www.openstreetmap.org/copyright https://www.floodmap.net/ -------------------- Music courtesy of the YouTube Audio Library: Rain Cloud Music - Emily A. Sprague Sunrise Over Big Data Country - Dan Bodan A Slow Dream - Emily A. Sprague Stuck In The Air - The Tower of Light Ammil - The Tides -------------------- Images of, and from: Afon Glaslyn and Traeth Mawr by Bill Boaden, CC BY-SA 2.0 https://creativecommons.org/licenses/by-sa/2.0, via Wikimedia Commons A sea of grass, south-west of Tremadog by Christine Johnstone, CC BY-SA 2.0, via Wikimedia Commons Cnicht From the Cob, Porthmadog, Gwynedd by Peter Trimming, CC BY-SA 2.0, via Wikimedia Commons "Island" near Farmyard by Dewi, CC BY-SA 2.0, via Wikimedia Commons Y Cob, Porthmadog o'r awyr, Gwynedd, Cymru (Wales) by Llywelyn2000, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons all other images are public domain, via the Yale Center for British Art, the British Library, and the National Library of Wales #wales