Bay Rock is a small islet off the northwestern coast of Magnetic Island. A lighthouse was erected there in 1886 and was used by vessels heading for the quarantine station anchorage at West Point.
The lighthouse was originally manned and the keeper and his family lived in a small cottage nearby. The last keeper, John Albert Edward Lawson was lost at sea when the small fishing boat Rialto capsized on 8 March 1920. Following Lawson’s tragic death the lighthouse was demanned and the light converted to an automatic acetylene gas burner. In the 1980's the lighthouse was deactivated and it was relocated in 1992 to the Townsville Maritime Museum where it remains on display today.
At the reference point waypoint there are remnants of the lighthouse and a plaque remebering Lawson.
The geology of the islet also proves interesting...
A natural arch, natural bridge, or (less commonly) rock arch is a natural rock formation where an arch has formed with an opening underneath. Natural arches commonly form where inland cliffs, coastal cliffs, fins or stacks are subject to erosion from the sea, rivers or weathering.
On coasts two different types of arches can form depending on the geology. On discordant coastlines rock types run at 90° to the coast. Wave refraction concentrates the wave energy on the headland, and an arch forms when caves break through the headland. Two examples of this type of arch are London Arch—previously known as London Bridge—in Victoria, Australia, and Neill Island in the Andaman Islands, India. When these arches eventually collapse, they form stacks and stumps. On concordant coastlines rock types run parallel to the coastline, with weak rock such as shale protected by stronger rock such as limestone. The wave action along concordant coastlines breaks through the strong rock and then erodes the weak rock very quickly. Good examples of this type of arch are the Durdle Door and Stair Hole near Lulworth Cove on Dorset's Jurassic Coast in south England. When Stair Hole eventually collapses it will form a cove.
At Bay Rock you will find an example of a small arch with a small cove beyond, which reminds me of 'smuggler's coves' often seen in the movies.
To claim this earthcache visit the listed coordinates and answer the following questions based on your observations.
1. State whether you think the coastline is discordant (at 90°) or concordant (parallel) and how you came to this conclusion.
2. Suggest how the arch was formed and describe the visible differences in the rocks at GZ, particularly the 'bridge' which enabled this formation.
3. Estimate the length, width and depth of the cove beyond the arch. How do you expect the cove to change over time?
4. Take a photo of yourself or something that identifies you at GZ.
Congratulations to Willis007, Beardman75, Karicka and Chamad for being the FTF.
