More than a hill Rottnest Island, Western Australia, Australia
By Rottnest Islander on 11-May-15. Waypoint GA7205

Wadjemup Hill is the perfect vantage point to see the complex formation of the chain of islands which are emergent features of a limestone ridge that once connected to the mainland. You’ll also discover the dune formations and the rocky limestone outcrops of the bays which make Rottnest in its own right geologically significant.

Earth Sciences Lesson: Geological Material

Rottnest Island is characterised by alternating limestone headlands and bays with white sandy beaches, flanked by sand dunes. The Island originated as coastal sand dunes, now cemented into a sedimentary rock called limestone.

Limestone on the Island is broken down into three distinct types:

• Tamala Limestone, oldest dated at 140 000 years.

• Rottnest Limestone, oldest dated at 132 000 years.

• Herschell Limestone, oldest dated at 8 000 years.

This means that Rottnest Island is composed entirely of rocks less than 150 000 years old, which formed during what geologists refer to as the Pleistocene and Holocene epochs.

Further Reading: Guidebook to the Geology of Rottnest Island by Phillip E. Playford.

Questions:

1. Looking southeast describe the predominant landform feature of the landscape in two to five words.

Instructions and How to Verify Your Find

Once you complete the “More than a Hill” 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 and cache name 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.