Earth Sciences Lesson: Geological Material
These beautiful lakes cover approximately 200 hectares, one tenth of Rottnest Island. The lake system consists of 7 permanent lakes and 5 smaller lakes, which usually dry up in the summer. Government House, Herschel and Serpentine Lakes are some of the deepest permanent natural salt water lakes in Western Australia.
There were once 8 fresh to brackish water swamps on the island, which formed important habitats and watering points for the native fauna. However, all but three of these were excavated during the 1970s to obtain road-building material, thereby converting them to hypersaline pools and eliminating their fresh water biota.
A microscopic algae called Dunaliella salina is common in the open water of the lakes.
It grows on salt crystals. This algae contains beta-carotene, a red/orange substance which is partly responsible for the pink colour of the smaller lakes. Beta-carotene also gives the brine shrimp their red appearance as they feed on the algae.
Further Reading:
Guidebook to the Geology of Rottnest Island by Phillip E. Playford.
Question:
- The lake in front of you is remarkably pink compared to others nearby. Explain why?
Instructions and How to Verify Your Find
Once you complete the “Shades of Pink” 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 GC5VBBT and cache name (Shades of Pink) 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.