Seamill Moraine
Cumbria has a rich and varied geology which contributes immensely to its variety of landforms and landscapes.
The High Fells and uplands of the Lake District dominate the county and comprise Ordovician marine sediments and outpourings of lava and ash from volcanoes. Large masses of igneous rock were intruded into these rocks during the early Devonian.
Surrounding the central core of the Lake District is a ring of rocks spanning the Carboniferous Period. These include the distinctive Carboniferous Limestone, which forms the limestone scenery of the Kent Estuary area and the Cumbrian part of the Yorkshire Dales area around Kirby Lonsdale.
The overlying Upper Carboniferous sandstones and shales of the Millstone Grit and the mudstones, shales and sandstones of the Coal Measures form a broad band of outcrop from the coast north of Whitehaven to the north of the Lake District. The lower land around the Solway Firth in north Cumbria, the Carlisle Plain and Vale of Eden are floored by mudstones and sandstones of Permian and Triassic age. These outcrop on the coast in the St Bees area, where they form the well-known red sandstone cliffs.
Over the last two million years the climate of Britain has varied tremendously with periods of temperate climate interrupted by repeated advances and retreats of glaciers and ice sheets. Collectively these periods have become known as the Ice Age (we are still in one of the temperate phases) and the actions of the ice sheets have been instrumental in forming the landscape we see today.
The landscape of Cumbria, and, in particular, the much loved mountains and valleys of the Lake District, were shaped by the enormous erosive forces of the glaciers and ice sheets of the Ice Ages of the past 500,000 years. Huge amounts of material were deposited by the ice sheets over the landscape leading to the formation of the undulating and hummocky lower-lying ground around the Lakes and resulting in very limited outcrop of the underlying rocks in these areas.
Apart from the peaks and fells of the Lake District, much of the bedrock geology of Cumbria is mantled by sediments deposited during the Ice Age by ice sheets moving over the area or from glaciers originating in the area. Perhaps, nowhere else in England is evidence for the tremendous landscape-shaping forces of the Ice Age more evident than in the glacier-scoured U-shaped valleys of the Lake District and the upland corries and craggy outcrops.
These valleys were carved out during the last main glacial period, the Devensian, some 12,000-50,000 years ago and are now occupied by the famous lakes such as Windermere and Coniston Water. There is a vast array of glacial deposits, mainly of till (boulder clay) lying over the surface of the County, deposited from beneath ice sheets and glaciers. The composition of the till varies depending on where the main ice flow was from, so that till over parts of northern Cumbria contains material derived from Scotland, while the Carlisle Plain received ice and its debris from the north, south and probably east.
During the melting of the last ice sheets and glaciers, over some 15,000 years, large amounts of material were released and transported by the meltwaters to form large spreads of fluvio-glacial sand and gravel deposits. Arctic, tundra-like conditions would have prevailed for the first few thousands years and during this time earlier glacial deposits would have been subject to repeated freezing and thawing leading to the formation of deposits of shattered bedrock (known as head) and large scree deposits.
The Lower Triassic St Bees Sandstone is magnificently exposed on the coast in the St Bees area (e.g. at Fleswick Bay). The succession is dominated by red to buff sandstones which show structures demonstrating that they were deposited by a sandy, braided river that crossed the Triassic desert plain. Other features shown in cliff section include conglomerates produced by current erosion, and soft sediment deformation structures which were produced by water escaping from the sediment after deposition.
The cliffs of the St Bees golf course and further south are a site of considerable importance for interpreting Late-Devensian glacial events and Late-glacial environmental conditions in northwest England. Coastal sections in a belt of hummocky deposits have over the years revealed a succession of interbedded tills, sands and gravels. Although interpretations differ in detail,
parts of the succession have been referred to a re-advance of Scottish ice on to the Cumbrian coast.
At the west end of the St. Bees valley are the terminal moraines of the last glacier(12 - 14,000 years ago). These unprotected cliffs are one of the best places in England to look at a freshly-eroded cross-section of a glacial moraine. Several huge "erratics" are visible in the shingle.
Large boulders are released from the moraine cliffs as they are eroded by the sea.
Canyons are formed in the higher moraine cliffs. Poor surface drainage due to large lodes of clay assists the erosion. The huge variety of shingle on the beach is testimony to the distances this material was carried; from both Scotland and the Lakeland fells, and it is replenished by the continual erosion of the cliffs.
At the foot of the shingle the ancient peat beds containing petrified trees can be seen after a scouring tide.
St. Bees is therefore a key site both for assessing the evidence for a readvance of Scottish ice.
Thanks to 2 Bees or not 2 Bees:- for this link
To claim this earthcache you will need to perform four tasks:
1. Estimate the height of the cliff at N54 28.982 W3 35.632
2. Take photo of cliff showing the banding.
3. Take a photo of GPSr on an erratic.
4. Finally, these unprotected cliffs are retreating at approximately how much each year?
Message the answers to the two tasks to me at the same time as you log your find. Post your pictures with your log. Any logs that don't fulfil this criteria will be deleted.