GC460Q5 STONE CHUTES (Earthcache) in Southern Scotland, United Kingdom created by Fungimanforager

GC460Q5 ▼

A cache by Fungimanforager Message this owner

Hidden : 2/15/2013

Difficulty:

Terrain:

Size: Size: other (other)

Join now to view geocache location details. It's free!

Watch

How Geocaching Works

Please note Use of geocaching.com services is subject to the terms and conditions in our disclaimer.

Geocache Description:

As an EarthCache, there is no “box.” You discover something about the geology of the area. For more info about EarthCache's take a look at www.earthcache.org

This cache was placed with the kind permission of :

SNH designates SSSIs under the Nature Conservation (Scotland) Act 2004. SSSIs are protected by law. It is an offence for any person to intentionally or recklessly damage the protected natural features of an SSSI.

STONE CHUTES

P-forms carved by ice abrasion and subglacial meltwater during the last glaciation (10,000 years ago) at Loch Treig, Grampian Highlands, Scotland. Photo M. J. Hambrey.

WE ASK OURSELF.
WHAT ARE THEY?
HOW WERE THEY FORMED?
WHAT CAN THEY TELL US? .

IS THE JURY IS STILL OUT?

It is by teaching that we teach ourselves, by relating that we observe, by affirming that we examine, by showing that we look, by writing that we think, by pumping that we draw water into the well.
Henri-Frederic Amiel (1821-1881) Swiss philosopher, poet.

P- FORMS

What are P-Forms?

P-forms is a all encompassing term used to describe a multitude of depression and groove features that are caused by subglacial erosion. P-form is the short term for plastically molded forms by Dahl(1965),however some authors (Shaw, 1988; Kor et al., 1991; Sharpe and Shaw 1989),refer to these features as S-forms (sculpted forms).

The term sculpted form is used by authors who believe in the melt water hypothesis to distinguish them as features that were produced by melt water and where ice abrasion is a minimal factor.

These features can be found ubiquitously wherever there is exposed bedrock that has been worked by a warm-based glacierGlasser and Bennett, 2004 The quality of the p-form is directly related to the bedrock as well as further weathering which may have deteriorated the glacial erosional surface.

Till Slurry Abrasion Theory

This theory was put forward by Just Gjessing (1965) and involves a layer of saturated till underneath the glacier that would act as an abrasive material. The slurrying till would account for the polishing of these features and attempt to explain striations which follow P-forms as clasts are worked down the P-form channel. This theory is not widely accepted in contemporary P-form interpretation however it should not be ignored as a possibility.

Map Showing P-Form Locations.
OFF ROAD PARKING ON ROUTE

Meltwater Theory

Many P-forms have been found throughout the shield that do not have any striations and appear to be completely meltwater derived (Shaw, 1988).

The morphology of P-forms have the appearance of a fluvial derived form exhibited by sharp lips (rims) that would be difficult to be produced by debris-ice erosion (Sharpe and Shaw, 1989)

One piece of evidence that seems to support the meltwater theory is that P-forms will travel transversely to the ice flow direction suggesting that they were not created by the ice it self (Benn and Evans, 1998).

Field measurement of the orientation of 142 channels shows that they are consistently orientated parallel to the direction of ice movement as indicated by striae, and striae are present on the floors and sides of many of the channels.

The mode of origin of the p-forms is discussed and it is concluded that meltwater erosion by corrasion and/or cavitation is the most likely process with active ice later moving through them. It may be significant that the p-forms occur along the former boundary zone between mainland and Mull ice

Sichelwannen are arc shaped p-forms which exhibit two arms that end in points on either side of the arc. These pointed arms face towards the direction of ice flow as the apex of the arc points up-ice. These are one of the most common p-form of their scale.

Once Sichelwannen become elongated they can be referred to as hair pin erosion marks.

Sichelwannen are similar to comma forms, the difference being is that Comma forms only have one arc arm and thus resemble a check mark.

Conclusions

Scarisdale is the best example in Britain of an assemblage of small-scale features of erosion known as p-forms. These are smoothed grooves, channels and scalloping in the bedrock.

The range of features present and their clarity of detail provides an unrivalled opportunity to test the different explanations proposed for their origin.

The most likely of these is that they were formed by a combination of glacial meltwaters and moulding by overlying glacier ice, and therefore they may allow a reconstruction of aspects of glacier hydrology.

Earthcache Task

LOGGING REQUIREMENTS

EXAMINE AND DESCRIBE FORMATIONS

1. Examine the location at Waypoint 1 and 4 and measure the width and length of the largest example of a 'SICHELSWANNEN'. Please Email this information to me but do not include this information in your log.

EXAMINE AND DESCRIBE FORMATIONS

2. Visit the location of Waypoint 2 examine the long P-Form that from ground level appears to run into the sea. Measure the drop at the lowest (seaward) end and email the distance, height from the end of the P-Form to shore level. Please Email this information to me but do not include this information in your log.

EXAMINE AND DESCRIBE FORMATIONS.

3. Visit Waypoint 3 and email to me your estimated Width, Height of the Walls and Length of the Largest Channel . Please Email this information to me but do not include this information in your log.

THERE ARE MANY OPPORTUNITIES FOR PHOTOS SO WHY NOT POST THEM IN YOUR LOG AND INCLUDE YOUR GPS TO PROVE THE VISIT.

Please email your answers to me and do not wait to post your log. I will always verify your answers as soon as possible and contact you if there is a problem.

Please do not post your answers on your log.

Click hereTO VIEW THE SNH FOSSIL CODE.

Click hereTO VIEW COMMON FOSSILS, ROCKS & MINERALS.

Click hereTO VIEW GEOLOGICAL FIELDWORK CODE.

FURTHER READING AND REFERENCE:

For more historical info: see: RCAHMS Argyll Volume 3 (Her Majesty's Stationery Office Edinburgh 1980) ISBN 0 11 491591 1

Click here To Read:Subglacial meltwater erosion at Loch Treig. Synopsis(OU).

Click hereTo read: Erosion of Bedrock by Subglacial Meltwater.

Click hereTo read: 6.1.4 P-Forms and Micro Channel Networks. Glacial Geology - Ice Sheets and Land Forms - Glasser and Bennett

Click here To read: Canadian Landform Inventory Project - P-Forms

Click herejncc.defra GCRsite account Scarisdale

Click here for copy of ppt Glacial Erosional Landforms slide show notes

Click here for copy of ppt Quartenary Erosional Landforms slide show notes

Scottish Journal of Geology, March 1981, v. 17:39-47, doi:10.1144/sjg17010039

I have earned GSA's highest level:

Additional Hints (No hints available.)

Watch

Geocache Description:

Attributes

Inventory

Bookmark Lists

STONE CHUTES EarthCache

Watch

Geocache Description:

Attributes

Inventory

Bookmark Lists