This rock is named after the Swiss geologist, Louis Agassiz who first noted the effects of ice on this rock in 1840. After a tour of various parts of Scotland examining rocks for evidence of glaciation, it was here he exclaimed "This is the work of ice!". It was the first time that glacial action had been recognised in a place where there was no ice currently, and led to the formulation of theories about glaciation and the Ice Age.
The upper part of the rock shows the characteristics of the Andesite lava that was quarried nearby. The andesite is dark purplish-grey with a very fine grain, and breaks into smooth blocks due to closely spaced cracks.
The lower part of the rock is very different, being undercut, and smoothed and polished by ice. There are grooves cut into the rock by the movement of the ice known as striations. Much of the evidence seen by Agassiz has gone due to rock falls, but there is a good example at the cache coordinates.
The geological significance of this spot is not only in it being an example of ice-smoothed rock, but also its place in geological research history, that of the first place where the effects of ice were noted in a place where now there is no ice.
To log this cache, please email me with the answers to the following questions:
- Estimate the height of the rock
- Estimate the depth of the undercut at its maximum point
- In front of the cache location is an example of the striations caused by the flow of ice. Can you explain how these lines in the rock might be caused?
- Optionally, post a photo of yourself or your GPSr beside the rock.
Your log will be deleted if I do not receive the answers to these questions.
Further information is available at these Scottish Geology and Edinburgh Geology Society pages.