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Portknockie Harbour

A cache by Highland 'Rocky'Haggi Send Message to Owner Message this owner
Hidden : 08/18/2017
Difficulty:
2.5 out of 5
Terrain:
2 out of 5

Size: Size:   other (other)

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Geocache Description:


 

Portknockie was founded in 1677 and became a significant herring fishing port during the nineteenth century. The village still retains many of the features and charm of its fishing heritage days and is a great place to spot dolphins. Portknockie is an historic natural harbour with two basins, it was home to over 150 fishing boats at its height and is today one of the Moray Council's four leisure harbours

The coast at Portknockie features an intermingling of Cullen quartzite formation ( Grampian Group)  (dating from Lower Dalradian times, 650 million years ago during which time they’ve transformed from sedimentary sandstone through partial volcanic metamorphosis) and the usual Highland psammite and semi-pelite.

Standing by the paddling pool and looking  directly across the harbour at the rocks both sides of the garages, you will see much folded rock ~ under stress flat lying layers of sedimentary / volcanic rock  become bent into a series of folds, the process results in a shortening and thickening of the crust. There are different fold types.

a) Anticlines ~ upfolded forms, results in older rocks becoming enclosed within the younger strata.

b) Synclines ~ downfolded forms,results in younger rocks becoming enclosed within older strata

c) Symmetrical folds ~ both limbs of the fold dipping at the same angle away from fold axis

d) Asymmetrical folds ~ both limbs of the fold not dipping at the same angle away from fold axis

e) Overturned folds ~one limb of fold has been tilted beyond vertical

f) Plunging folds ~ axis of fold is tilted

g) Domes ~ more or less circular equivalent of anticline, oldest rocks exposed in centre of dome

h) Structural basin ~ more or less circular equivalent of syncline, youngest rocks exposed in centre of dome.

 

Anticlines and Synclines are the up and down folds that usually occur together and are caused by compressional stress.Anticlines are folds in which each half of the fold dips away from the crest.  Synclines are folds in which each half of the fold dips toward the trough of the fold.  You can remember the difference by noting that anticlines form an “A” shape, and synclines form the bottom of an “S.” In anticlines, as seen on the ground, the oldest rocks are in the centre of the fold.  In synclines, the youngest rocks are in the centre of the fold.

There are various processes and forms of eroded structural folds ~ Anticline and syncline ridges and valleys, unbreached and breached anticlines. Unbreached is where the resistant folded layers are undissected along the axial plane and fold and breached is the opposite where the folded layers along the axial plane of fold are incised by erosion, such that the  former crest has become a valley flanked by inward facing slopes/cliffs

 

To claim this EarthCache, please send the answers to the questions below to us by email /message centre, do not post in your online log. Your log may be deleted if these criteria are not met. It is helpful if you send your answers and log at the same time. Educational guidelines for EarthCaches are set by Geocaching.com and GeoSociety.org (EarthCache) and have to be adhered to.

 

 

1) From the paddling pool area, look at the rocks across the harbour on the North East side west of the garages to the lifebuoy. How would you describe them and what do you think has happened to cause this?

2) At the lifebuoy (N57.42.313 W002.51.741) how many layers can you see and at what angle are they laying?

3) How thick are the vertical layers within the horizontal layers?

4) In the dip to the right of the lifebuoy what is in/on the rock?

5) Roadside, directly across from the garages, is the rock formation an anticline or syncline?

6) While not compulsory it is always good to see photos from your visit

 

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