Looking across from GZ you will see an island. Looking at the banks of this island you will see that they are made up from boulder clay. Boulder clay is a deposit of clay, usually full of boulders. If you look carefully you will be able to see small boulders sticking out at various points. The boulder clay found here will probably have been formed beneath glaciers and ice sheets during the Glacial Period of northern Europe.
An ice sheet scrapes the clay from the top of older rock. The ice sheet also pushes rocks, stone and boulders in it's path and this is how boulder clay is formed. The colour of boulder differs depending on what type of rock it has been mixed with. It can be red from 'Old Red Sandstone araes, black from carboniferous rocks, white and chalky from chalk, blueish-grey, grey or buff from Silurain rock. Although once it has been exposed to weather it can often turn brown.
The name 'boulder' clay may be misleading as the 'boulders' can range in size from small pebbles to those that weigh many tonnes in weight. They often have a smoove or flat side where the ice sheet has smoothed it during the glacial shift. Where hard rocks are to be found, these can often have grooves and dints in them where they have been rubbed against other rocks in the glacial shift.
Different types of rocks can be found in boulder clay and rocks from other countries have been found as the ice sheet has moved across countries and continents. Here in the East of England, Scandinavian rocks have been found showing the glacial shift route.
To be able to log this cache you will need to message me with the answers to the following questions
- What colours can be seen in the clay around the edge of the island? What type of rock or minerals do you think this boulder clay moved through to become this colour?/li>
- Look down, describe what it is you are standing on. Do you think it originated here or could it have been moved here by the glacial shift?
- From GZ how far away is the island?
This cache has been placed with kind permission of North East Lincolnshire Council.