Ancient lava flows
Lead by Josephine Drake four members, David Turner, Ian Hughes and Jim Hutchinson travelled to Eycott Hill, which is situated just North of the A66, midway between Penrith and Keswick in northern Lakeland.
Eycott Hill was shaped by volcanic activity; over 20 ancient lava flows, each formed by different eruptions, tilted and eroded to create a landscape of ridges and hollows. The volcanic rocks are well exposed in typical trap topography of successive scarp and dip slopes.
Approximately 460 million years ago in the late Ordovician, sub-aerial lava flows poured from fissures much as we see today in Iceland and Hawaii, and consist of an 800 m-thick succession of continental margin-type tholeiitic lavas and interbedded volcaniclastic rocks.
Much of the lava is black, fine grained andesite containing very small crystals, but the site is perhaps best known for the ‘Eycott-type’ coarsely porphyritic rocks that contain felspar crystals locally more than 2 cm long. It is nice to see these rocks in situ but a large example has been left at a display area so no-one leaves disappointed.
For much of the year the hollows between the ridges are very wet and can cause problems for visitors but following a long spell of fine weather members were able to wander freely which added to the enjoyment of the visit.
Cumbria Wildlife Trust, ‘Eycott Hill Nature Reserve’ visitor leaflet.
‘Eycott Hill’ by D. Millward. Extract from the Geographical Conservation Review, Vol.17, Chapter 4: Lake District and northern England. Available to download from the internet.
I am grateful to Dr Drake for the notes provided.
Images and text J. Hutchinson,