Earth Sciences Lesson: Geological Material
Coastal processes have been active since the coastal lime dunes were deposited and lithified into rock (limestone), but became dominant when present day sea level was reached. Coastal dunes can be divided into 4 unique zones. Each zone has different aspects that make it more or less habitable for different organisms. The beach, foredune, trough (or swale), and hind dune are all part of the coastal dune system.
Beaches are zones where water meets land. Constant wave action, wind, and rain make this an extremely difficult habitat for organisms to survive in. The foredune is the area directly behind the beach. Reeds, grasses and spinifex help stabilise the sand here to create an almost habitable area for plants and animals. Wind blows through the coastal dunes, forming a depression between the foredune and the hind dune. This area is called the trough (or swale). The trough often fills with groundwater causing interdunal ponds where many organisms survive in this more stable habitat. Just behind the trough is the hind dune. The hind dune is usually forested and provides shade to its inhabitants. The hind dune provides cool temperatures and moist soil adequate for many plants and animals.
At Geordie Bay changes in the foredune system due to erosion are posing a risk to buildings on the front row of accommodation as, during the coastal development an inefficient buffer was allowed for. This is particularly significant during storm events.
Further Reading:
Guidebook to the Geology of Rottnest Island by Phillip E. Playford.
Questions:
- Suggest how the developer could have overcome the structural issues we are now facing with the movement of the foredune?
- Name 3 methods used here to stabilise the foredune.
Instructions and How to Verify Your Find
Once you complete the “Cache with a view” Earth Cache 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 GC5VBC9 and cache name (Cache with a view) 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.