Limestone deposits from former algae reefs
Welcome to the magical world of geology in Crete. Here you can get to know great geologically interesting places and thus a lot about our earth. We love Crete, nature, people and many other things have fascinated us for years. Maybe you already know one or the other earthcache from us. Today we would like to show you another interesting topic.
Due to Crete's variety of rock types, you can also find limestone and the resulting karst landscapes there. Other geologically interesting phenomena can arise from this limestone. Limestone tuff, limestone sinter and travertine can be formed through dissolution processes.
In addition to processes of physical weathering, chemical processes of carbonic acid weathering take place during formation. Carbonated water dissolves components of the limestone and promotes them further. These can then be redeposited in different ways and have different appearances.
However, such dissolved sediments can also have another type of deposit in the form of algae reefs (coral reefs). They are then formed by cyanobacteria (blue-green algae). These trap the sediments with their mucus and gradually form small lumps. To do this, however, they require a relatively high flow speed in order to be able to capture enough sediment. Such ocean currents are reached in places with more steeply sloping sea depths, which is the case around Crete. So under the right environmental conditions, reefs can form and grow. Other sediments can also play a role and the appearance can also vary. Ultimately, the sediments form the “skeletons” of the corals.
Over the course of millions of years, tectonic plate movements can cause dead algae reefs (coral reefs) to reach the surface. The deposited sediment lumps then become visible. In their nature they are similar to limestone tuff and limestone sinter.
How do i get here and what should i bear in mind?
Please note that to get to this earthcache you may have to do a longer hike. You can also take a boat to the “sweet water beach” at certain times of the year. From there it's shorter. However, the evaluation of the cache is based on the route on foot. That's why you should take plenty of drinks with you during the warm season! You should also be sure-footed on mountain slopes. If you come from Chora Sfakion, you shouldn't be afraid of heights either.
Your tasks:
In order to be allowed to log this Earthcache, please send us the answers to the following questions via the message center or by email. If something is wrong, we will contact you. Look for this location/the large rock (the GPS is not particularly accurate here on the mountainside) Pay attention to the spoiler picture!
1. Once you find the lumps, what vegetables do they remind you of?
2. Take a coin, hold it next to the nub and take a picture of it. Send this to us (not in the log!).
3. What is the relationship between the size of the nub and the coin?
4. Look around in the surrounding area, can you find any other rocks with the same structures? How many ?
5. Look around, where do you think the rock comes from, or has it always been here?
6. If you look at the rock around the nubs, what does its color and structure remind you of?
7. Estimate the height from your location to the sea surface
8. Which bacteria were necessary to form these deposits?
9. A picture of you on the way here without spoilers! Either to the log or to us with the answers.
Have fun and enjoy the location :-)
Source: own observations/Wiki