An intersting site in the Fitzgerald River National Park that we thought needed an earthcache.
The Ravensthorpe Range is a layered succession of volcanic and sedimentary rocks that were altered, folded and pushed up through the Yilgarn granite into a dome that has since largely eroded away. Its slopes and ridges feature a mix of rock types including greenstone and banded iron formations.
The tilted rocks that form the coastal peaks and headlands began as silt and sand deposited in river deltas and shallow sea around 1700 million years ago. 400 million years later when the continents collided, these rocks were altered by extreme heat and pressure. Siltstone was transformed into schist and sandstone to quartzite, a much harder rock.
About 35 million years ago marine sediments rich in the remains of sponges became 'spongolite'. This soft rock, which forms a veneer over much of the park, has been eroded by water to create striking multi-coloured breakaways.
During the last two million years, wind blown dunes of shelly material formed along an everchanging coastline. this was cemented together by rainfall and turned to limestone. Around 18000 years ago the sea level rose drowning the coastline and creating todays beaches and inlets.
To log this cache, go to the listed coordinates and email me the answers to these questions. You can immediately log the find and if there are any problems I will contact you
Q1. Looking towards the ocean there is a large outcrop to your right. Describe how the rocks at the base vary from the rocks at the top of the outcrop and explain why they are different .
Q2. What is 'spongelite'?
Q3. At GZ there is an interpretive sculpture. What are the two materials it is made of and what does it represent?