Professor Mike Rosenbaum gave a very interesting talk as he took us back through time looking at some of the events that have led to the development of the Shropshire Landscape that we see today.
The talk commenced by looking at the effects of glaciation. The Anglian glaciation ( commenced 450,000 years ago) was the most extensive but in Shropshire and in Powys it’s effects were obliterated by the later Devensian glaciation (commenced 100,000 years ago). The Devensian ice moved Eastwards from Wales meeting the Irish sea ice from the North. During this period features eg. the Berwyns stuck up from the ice as Nunataks. This ice retreated about 20,000 years ago.
One noticeable effect of this ice is the Iron Gorge which was cut by a sub-glacial river and this has produced a gorge that has very steep sides. The steepness of the sides leads to instability and landslides have occurred and the land is still slipping.
One other very interesting idea that was discussed is one that arose from observations made by OT Jones in 1951. He observed that the river systems in Wales are radially centred on a high point in Anglesey. Later Brown in 1960 observed that that there is a wide elevated plateau covering central and southern Wales and the Marches. It has been suggested that the cause for these observations is due to the fact that the region was once over an ancient mantle plume. Luckily it is now inactive!