Maltese cliffs are made of soft limestone layers which slowly erode as they interact with the sea.
There are 5 different layers
- Lower Coralline Limestone
- Globigerina Limestone
- Blue Clay
- Greensand
- Upper Coralline Limestone
The ones at the bottom are the oldest (lower coralline limestone), the first having been deposited around 35 million years ago while the most recent layers (upper coralline limestone) are much younger, around 7 million years.
A spectacular example of the rock layers can be seen at the Dingli Cliffs on the West coast.
Each of the layers has its own characteristics
1. Upper Coralline Limestone is hard and rough with cracks and is white/grey coloured. It is used for road surfacing and building.
2. Green sand is the thinnest rock layer, orangey coloured (Yes it is only green before it is exposed!) and crumbly. It usually contains marine fossils.
3. Blue Clay is a soft rock that quickly erodes and is bluey grey in colour. It sticks to your boots and makes you grow taller when you walk on it!
4. Globigerina Limestone is harder then blue clay, but softer then Upper Coralline Limestone. White/yellow in colour it is used for building and also sculptures.
5. Lower Coralline Limestone is the oldest rock. Hard and white/grey coloured. Mainly used for roads and concrete.
Coastal boulder scree areas are formed as the Blue Clay erodes and the Upper Coralline Limestone is weakened causing cliff edges to collapse under their own weight. The boulders then slide downwards over the clay and boulder scree thus results at the base.
If all the Upper Coralline Limestone falls then the Green Sand and Blue Clay quickly erode down to the surface of Globerina Limestone, If erosion is not stopped by stonewalls, the soil is washed away. As you travel around the central plateau of Malta you will notice many examples of boulder scree slopes that have been cultivated and stone walls have been placed in strategic places to help prevent this happening.
Here, as you can see from the photos, the slopes are rather gentle and have in places been cultivated and terraced, if you continue around the coast towards Selmun Off-road Cache GC48BJ4 (note that you can only go on foot from here) you will find more dramatic examples of the fallen boulders, and cultivation becomes impossible on slopes such as these, the Blue Clay being very much in evidence.
According to Wikipedia: Formation of scree results from physical and chemical weathering and erosional processes acting on a rock face. The predominant processes that degrade a rock slope depend largely on the regional climate (temperature, amount of rainfall, etc.). Examples include:
Mechanical weathering by ice
Chemical weathering by mineral hydration, dissolution, and salt deposition
Thermal stresses
Topographic stresses
Biotic processes
Interestingly, the cliffs in this area support a diverse range of fauna including a particular plant, The Maltese Stock, which, in Malta, is only to be found at Ix-Xaghra tal-Kortin and the adjacent Tal-Mignuna area.
Much of this information has been sourced from "Natura 2000" - a network of protected areas across the European Union. Malta has designated a total of 39 Natura 2000 sites.
In order to log this cache, please send us an email or message via Geocaching with answers to the following questions
1 Walking along the path, examine any of the boulders. What colour is the boulder you have chosen? Tell us how it looks and feels to the touch.
2 Rock formations on Malta consist of five basic layers, which layer do you think your boulder is from? And why do you think this?
3 According to the information board at GZ, by what name is boulder Scree known locally? PLEASE NOTE we have been advised that the information board is no longer in situ. Others have answered by using the internet, please try if you can!
4 How do you think the boulder scree has formed here? Looking around you, can you see man's involvement in the landscape? Please tell us your observations.
We would appreciate it if you could upload a photo with your log but of course this is not compulsory
You do not have to wait for a reply in order to log the cache, we will let you know if there is a problem. However, if we do not receive your mail then your log will be deleted.