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Ardersier Glacial Deposits SSSI

A cache by Gerryu2 Send Message to Owner Message this owner
Hidden : 10/21/2011
Difficulty:
1.5 out of 5
Terrain:
1.5 out of 5

Size: Size:   not chosen (not chosen)

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Geocache Description:


There is little doubt that Ardersier owes it's existence to the upheaval brought about in the aftermath of the Battle of Culloden. In the 1750's the parish of Ardersier was sparsely populated and only small scattered hamlets would have existed in the area. One such small fishing hamlet called Blacktown was unfortunate enough to have settled close by the spot where the millitary engineers of the time decided to build "Fort George". From there, it was planned that over 3,000 Hanoverian troops could be rapidly deployed to repress any future sedition. As can be seen today, the Fort is a massive structure complete with it's own moat and defence system and is still in use.

That's the very brief local history lesson over with. Let's get on to the earthy stuff!!!

Not many people will realise that part of Ardersier is a designated site of special scientific interest (SSSI) due to the glacial deposits. The co ordinates will take you to a public car park with an information board about the wildlife etc in the area. It's a pity there are no such information boards in the area providing information on the Glacial Deposits. Across the road from the car park is a field with chickens and a hillside covered in gorse. This land is not immediately impressive to look at but this land and much further contains the Glacial Deposits.

So what is a Glacial Deposit?

Basically, an advancing ice sheet carries an abundance of material that has been plucked from the underlying bedrock and acquired on it's travels. The various unsorted rock debris and sediment that are carried or later deposited by a glacier is called till. Till particles typically range from clay-sized to boulder-sized but can sometimes weigh up to thousands of tons.

So what kinds of till do you get?

Moraines are deposits of till that are left behind when a glacier recedes or that are carried on top of alpine glaciers.

Lateral moraines consist of rock debris and sediment that have worked loose from the walls beside a valley glacier and have built up in ridges along the sides of the glacier.

Medial moraines are long ridges of till that result when lateral moraines join as two tributary glaciers merge to form a single glacier. As more tributary glaciers join the main body of ice, a series of roughly parallel medial moraines develop on the surface of main glacier.

An extensive pile of till called an end moraine can build up at the front of the glacier and is typically crescent shaped. Two kinds of end moraines are recognised, terminal and recessional moraines.

A thin, widespread layer of till deposited across the surface as an ice sheet melts is called a ground moraine. Ground moraine material can sometimes be reshaped by subsequent glaciers into streamlined hills called drumlins, long, narrow, rounded ridges of till whose long axes parallel the direction the glacier traveled.

Do you want more info on the history of the actual Glacial Deposits at Ardersier? Of course you do........

This site is located on the Ardersier peninsula on the east coast of the Moray Firth, between Inverness and Nairn. It forms part of a suite of glaciomarine ice-contact deposits and raised shorelines and includes an area of high ground consisting of contorted silts, sands and clays, trimmed on the north and west sides by a series of Lateglacial and Holocene raised shorelines. The deposits at Ardersier were first described in 1874 after being recorded near Kirkton. This was a small exposure of grey clay containing shells of arctic molluscs, which was either overlain by, or incorporated within a brownish deposit of gravel and silt.

The above mentioned features provide important evidence for interpreting the pattern of wastage of the Late Devensian ice-sheet, including a possible readvance, and the changes in relative sea level that both accompanied and followed the period of ice-melting.

It's been suggested that the deglaciation of the Late Devensian ice sheet in the inner Moray Firth area was interrupted by the “Ardersier Readvance”. Some evidence indicates that the Ardersier features were not produced by a major readvance of ice but more probably represent glaciomarine deposits formed while ice occupied the Inverness Firth. Similarly the Late Devensian shoreline sequence of the area does not support the readvance hypothesis; instead it suggests that the sediments were deposited as relative sea level fell and the ice mass retreated westwards.

TASKS
Your Earthcaching tasks are as follows:

1) At the roadside close to the co ordinates, look at the hillside and describe how the hillside looks from left to right.

2) Again, look at the hillside and estimate in metres the height the deposits rise to. It is thought that at one time, the deposits where 40m higher than they are now.

3) What type of Moraine do you think you are looking at and provide a reason why you think it is this type.

Send the answers to 1, 2 and 3 in an email to the cache owner via his profile. Do not post this in your log. Cachers can log the cache before receiving my confirmation email as any logs from cachers who haven't sent the answers will be quietly deleted!

Optional task: At the coordinates, take a photo of yourself and/or GPS with the colourful information board in clear view behind you and post this in your log. I would really love if you could do this to prove that you have actually visited and I enjoy seeing caching photos in my listings.

You must carry out these educational tasks as required by the Earthcaching organisation as a condition of logging the cache. Logs that do not adhere to these guidelines will be deleted without notification. See www.earthcache.org

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