Earth Sciences Lesson: Geological Material
During the summer the lakes will expose many colours from pinks, greens, blacks and even oranges – these colours reveal the secrets of the lake. Hidden beneath the water are active microbial mats. These mats are communities of organisms which inhabit the floor, and under the right conditions deposit limestone in the form of microbialites.
These seemingly insignificant communities are identified as highly valuable biodiversity assets as each community is unique. These mat communities are very similar to those that form stromatolites (e.g. at Shark Bay) and thrombolites (e.g. at Lake Clifton), which are modern equivalents of the earliest life forms on Earth.
The mats on Rottnest Island form living stromatolites in a few areas, if it is a calm day look out beyond the manmade limestone platform and you’ll be lucky enough to see some active stromatolites. A stromatolite (literally, ‘layered rock’), looks like a cross between a cauliflower and a rock. However, unlike rocks they are actually alive – each stromatolite has a top surface layer teeming with living, active cyanobacteria.
Further Reading:
Guidebook to the Geology of Rottnest Island by Phillip E. Playford.
Questions:
- The lakes support delicate and unique ecosystems and provide sustenance for many migratory birds. This closed system is threatened by human impact and shoreline movements. Looking around you note any human impacts which would have impacted on the lakes.
Instructions and How to Verify Your Find
Once you complete the “Secrets of the lake” EarthCache requirements you can post your find without delay, as per the EarthCache guidelines. You will, however, need to verify your find by sending me a message with the GC code GC5VBB4 and cache name (Secrets of the lake) on the first line and provide your answers to the questions listed below, otherwise your log may be removed.
Adhering to the EarthCache guidelines, please be careful not to include any detail in your log or photos that may assist others in answering the questions without actually visiting the sites and carrying out the fieldwork.
This EarthCache presents a good opportunity to practise CITO (Cache In Trash Out), so please bring a rubbish bag and help save the environment. Take a photo of the rubbish you collect along the way and include in your log for bonus geo-karma points!
Make sure you stick to the designated paths and leave no trace. Please do not interfere with the geological material, vegetation or wildlife – the tasks can be completed without the need to damage the environment.