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This cache has been archived.

geoawareUK2: As the CO has been banned by GCHQ and can not receive answers to the tasks, this cache no longer fits the rules for an EarthCache so I will have to archive the listing. If the CO sorts out his problems with GCHQ, it can be considered for unarchiving.



Dune and Dusted

A cache by gingerbreadmen Send Message to Owner Message this owner
Hidden : 04/09/2008
1 out of 5
2 out of 5

Size: Size:   other (other)

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Geocache Description:

These sand dunes are not difficult for any minimally fit person to climb but unfortunately are not accessible to wheelchairs or buggies. You can park within 50 metres of the above co-ordinates.

Parking is available at the nearby National Trust car park which is open from dawn to dusk. You have to pay to enter in a car but it is free to walk in or you can approach the site along the beach either from the north or south
Freshfield train station is only 1 mile from the reserve on the Liverpool-Southport line.

On the way why not stop off and feed the red squirrels in one of their last refuges in England, if you are lucky they will come up to you to be fed by hand.

The published co-ordinates take you to a notice board on the land side of the dunes, if you take it that this sign is at the eastern edge of the dune system follow the obvious route through to the shore where you will see a tall yellow warning marker.

To claim this EarthCache:
Post a picture of yourself at either the notice board or the yellow marker post with your log entry.
Calculate the width of the dune system from the above co-ordinates to the edge of the dunes near to the yellow marker.
Estimate/calculate (no need to climb it) how much higher than the beach the sand dune is at N53 33.891 W003 05.964, (that’s the one in front of you if you stand with the marker at your back, facing away from the sea.).
Send these two calculations to me via an e-mail, do not post them on your log.

Coastal sand dunes develop where there is an adequate supply of sand (sediment within the size range 0.2 to 2.0 mm) in the intertidal zone and where onshore winds are prevalent. The critical factor is the presence of a sufficiently large beach plain whose surface dries out between high tides. The dry sand is then blown landwards and deposited above high water mark, where it is trapped by specialised dune-building grasses which grow up through successive layers of deposited sand.
Sand dunes form in relatively exposed locations, and in a number of physiographic situations. The most common are bay dunes , where a limited sand supply is trapped between two headlands; spit dunes , which form as sandy promontories at the mouths of estuaries; and hindshore dunes , which occur in the most exposed locations where large quantities of sand are driven some distance inland, over a low-lying hinterland. This last type forms the largest dune systems in the UK. Less common types are: ness dunes , which build out from the coast; dunes on offshore islands , which are often superimposed on a base of other material such as shingle; climbing dunes where sand is blown up on to high ground adjacent to the beach; and tombolos , where a neck of sand is deposited between two islands or between a promontory and an island.

Sefton Coastal Dune System
The Sefton Coast is the largest dune area in England. It is a coastline subject to natural change.
At Formby Point the rate of dune erosion is up to 5 metres each year, whereas within a few kilometres to the north and south there is rapid growth of the coast.
Within the dune system, damage and interference by people have reduced the high wildlife interest, rates of natural change and free movement of sand dunes.

A History of Coastal Change
It is not known exactly when sand dunes began to form on the Sefton Coast, but an offshore sandbank or barrier beach did form around 8,400 years ago. This was well established by 6,000 years ago, and it is known that dunes started to form around 5,100 years ago.
In the distant past both humans and wildlife moved with, and adapted to, changes in the position of the coast. Between the end of the last glacial maximum (about 10,000 years ago) and Medieval times (about 600 years ago) the sea occasionally broke through the coastal dune barrier and flooded low-lying inland areas. These changes in the position of the coast are well recorded in layers of sediment, some of which are exposed on the beach around Formby Point.
Before the beginning of the eighteenth century the form of the coast derived mainly from conditions offshore. Maps and charts demonstrate the effect of recent human influence. Dredging, river training and coastline hardening have imposed a pattern of accretion and erosion on the shoreline where previous conditions were much more variable.
In more recent times the dunes have been partially stabilised by maintaining their natural vegetation. Pine trees have been planted, further stabilising the dunes, and artificial sea defences have been built to protect the developed shorelines. The inland lakes and mosses behind the belt of coastal dunes have been drained and claimed for agricultural production.

Physical Forces and their Influence
The predominant source of the Sefton Coast beach and dune sand is the bed of the Irish Sea. During the last glacial maximum (Devensian) advancing ice sheets pushed glacial deposits into the Irish Sea basin, and over 10,000 years these have been broken down, sorted and transported by tidal and wind-driven currents.
The prevailing westerly weather and tidal streams both tend to move seabed deposits towards the coast and into the river estuaries, which are both zones of net sediment accumulation. The river Mersey contributes very little sediment to the Sefton Coast; it is mostly intercepted in the Ship Canal. The river Ribble carries fine silt downstream which settles out on the northern Sefton beaches whenever, or wherever, sheltered conditions prevail.
A further source of estuarine accretion (infilling by sediment) is the sand eroded from Formby Point which is moved by tidal and wave-driven currents northwards into the Ribble estuary and southwards into the Mersey estuary.
Formby Point, midway between the Mersey and Ribble estuaries is the meeting zone of the two major estuarine regimes. Tidal streams converge offshore, with the result that a large intertidal sand spit (Taylor's Bank) has developed, aided by the construction in the first half of the 20th century of the river Mersey training walls.

Dune Growth and Erosion
At Formby Point there was extensive coastal erosion during the eighteenth century up to about 1830. This trend reversed dramatically in the mid-nineteenth century, when Formby Point moved out (accreted) about 300 metres around its whole arc. Landowners at the time took advantage of this period to assist the advance of the dune front by means of sand trapping fences and dune management, mainly the planting of marram grass. The remains of some fences can still sometimes be seen today on the beach near Fisherman's Path, Ainsdale.
Although the Altcar sand dunes and the dunes to the north of Ainsdale Sand Dunes National Nature Reserve are now accreting (moving out towards the sea), the sand dune system around Formby Point has experienced continuous erosion throughout the twentieth century.
The balance of evidence suggests that the present phase of erosion was primarily triggered at the end of the nineteenth century by a significant increase in the frequency of storm force westerly winds and destructive waves. The erosion was compounded by the effects of dredging, spoil dumping and training wall construction which significantly altered the bathymetry (shape of the seabed) in Liverpool Bay, leading to increased wave energy focusing on Formby Point.
This focusing is greatest to the north of Wicks Lane, (between Lifeboat Road and Victoria Road at the National Trust site). It particularly affects the National Trust frontage. Today the erosion rate is greatest at the boundary between the National Trust site at Formby and the Ainsdale Sand Dunes National Nature Reserve, with an average loss of approximately 4.5 metres per year over the past 20 years (1999 figures). Individual erosion events often result in a short-term loss of several metres. These events are generally transitory and conditions then settle back into the long-term trends identified.
Part of the Crosby and Southport shoreline has been partially fixed by coastal defence work. However, the natural forces remain at work and sand drift at Crosby is tending to bury parts of the sea wall, whilst sand dunes are developing in front of the sea wall north of Weld Road, Birkdale, near Southport. From Hightown to Birkdale the coastline is in a more natural condition, with generally wide sandy beaches still backed by an extensive system of sand dunes.

Future Changes
The Sefton Coast has to be considered in the light of the effect of possible climatic change - global warming, sea level rise and an increase in storminess. Numerous predictions have been made as to the magnitude of these effects, with widely differing answers. However, recent predictions have tended to come together in a narrower range. Recent climate modelling work suggests a possible rise in average sea level of 0.3 metres over the next sixty years. On top of this, the increase in maximum wave height and meteorological surge effects on any storm event must be considered.
Although the environmental influences and the directions of sediment movement are well understood, there is uncertainty over just how much sediment remains in the Irish Sea 'reservoir'. It is now believed that most dune systems in Europe are mature and in erosional and recycling phases. Knowing the sand budget (the total amount of sand in the system) is as important as the understanding of the living and non-living processes. Therefore, more research is needed to gain an understanding of how the Sefton Coast might respond to future climatic change.

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