by subglacial deformation or r emnant / erosional. There are two main theories of drumlin formation: constructional, in which the form of sediment is shaped i.e. They may have had possibly a length or width ratio of between 1:2 & 1:3.5 kilometres. These drumlins were typically one to two kilometres, less than fifty metres in height also below three hundred to six hundred metres in width. They formed near the margins of glacial systems or within areas of fast flow deep under Ice-sheets. Glacial landforms were composed primarily of glacial till. Drumlins may have comprised of layers of clay, silt, sand, gravel or boulders in various proportions. According to the classical sense it was an elongated hill in the shape of an inverted spoor or a half-buried egg that was discovered in glacial ice that had acted on unconsolidated till or ground moraine. Wonderful, wonderful! ‘ Drumlin Formationĭrumlin from the Irish word ‘ Droimnin’ or ‘ little ridge ’ was first recorded during 1833. Cusack included that the great nineteenth century author William Thackeray referenced Clew Bay a: ‘…the bay and the Reek, which sweeps down to the sea, and the hundred isles in it, were dressed up in gold and purple and crimson, with the whole cloudy west in a flame. He also discovered that Clew Bay was often referred to as a stunning example of a drumlin swarm…there are one hundred & forty-one named drumlins also countless unnamed tidal-islands. This occurrence resulted in the formation of drumlins from west to east with their massive clay boulder cliffs. As the temperature rose the ice retreated with wave-like patterns that left sediment on the land’s surface. Michael Cusack in his research for his book The Story of Clew Bay, from Granuaile to John Lennon stated in an article in The Irish Times 14 th June 2016 that some twelve thousand years prior to Granuaile Clew Bay was covered in ice. Drumlins of Ice debris left by ice-sheets formed when the sea rose then drowned the low land. The Clew Bay drumlin field proved how powerful ice was in the shaping of the landscape. This site includes a video of Clew Bay, its Islands, its people & the site’s formation from a BBC coast team. Collanmore Island near Westport is the largest island within the inner bay. Several of the hills on land around the bay are similar drumlins. They were formed when glaciers reshaped the landscape in the last Ice Age. The islands in Clew Bay are partly drowned drumlins, which are elongated, steep-sided hills that were sometimes described as whale-backed. Ĭlew Bay has according to tradition three hundred & sixty-five islands: one for every day of the year! The largest one Clare Island guards the entrance to the sheltered bay. Clew Bay Ireland coordinates are: 53.833333, – 9.8. Drumlins showed wave erosion that created till banks at the sea’s edge as the resultant sea level rose with the force of the melting glaciers. Several were steepest on the upstream side then trailed off towards the newly exposed ice-free area. An inverted spoon shape is the classic form, or a narrow ridge elongated in the direction of the ice flow. The glacier then pushed up over the debris with the ice moved forward. Drumlin is derived from the Irish word droiroimnín ( littlest ridge) Drumlins may be explained as features created while the Glacial Front melted back. One example is the Drumlin field of Clew Bay with Newport Bay on Mayo North Atlantic coast. In spite of its current moderate climate Ireland displays impressive features of past glaciation from periods of geologic history known as Ice Ages. Drumlins are usually three hundred metres long or perhaps possibly over one hundred metres wide. Smaller drumlins are in west Mayo where actually some are submerged in the Clew Bay area. ![]() As a result of the erosive work of slow-moving ice with depositional activity under the ice or at its margins it produced a huge impact throughout. Within Ireland the most recent of these glaciations saw ice perhaps on occasion more than a thousand metres thick over the land. The impact over several million years produced a series of glaciations that extended across much of western Europe. The name itself was derived from the Gaelic ‘druim’ a rounded hill or mound & first appeared during 1833. Drumlins either oval or elongated hills are believed to have been formed by the streamlined movement of glacial ice sheets across rock debris or otherwise known as till.
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