When visitors come to stay there is usually a request for a visit to "the" beach. It's a bit of a strange request really because people who live in the Nelson/Tasman area have at least 15 choices of beach to visit without travelling very far at all. The choice of beach depends to a large extent on the type of sediment deposited there, whether it be fine sand, course sand, pebbles or boulders. There are lots of options.
When you think about it, the type of sediment is decided by the geology of the area from which the material is obtained. The sediment at Ruby Bay originates from the cliffs overlooking the bay. They are from the eroding edge of the Moutere gravels deposit. The Moutere gravels deposit reaches depths of 300 metres and lies on gravels and igneous rock below. The clay and gravel was eroded by the uplifting Southern Alps on the Pacific Plate three million years ago. On the other hand, the Richmond Ranges to the east and the Arthur Range to the west are part of the Australian Plate and were uplifted approximately one million years ago. The Moutere gravel base was then eroded beside the mountains by new river systems, namely the Waimea and Motueka Rivers.
Ruby Bay sits on the seaward edge of the remaining Moutere gravels. The cliffs erode revealing embedded Pacific Plate sourced rock and petrified forest fossils. Some of the rocks you might find on the beach are shown on the information board at the given waypoint. They are also shown below.
To claim credit for this earthcache you need to answer three questions and you will also need to take a photo and post it with your log.
1. Why do you think this bay is called Ruby Bay? (Read the information above or the information board.)
2. What evidence is there that the stones are becoming smaller? (Think about the marble that has been brought here.)
3. What evidence is there that erosion is still occurring?
4. Collect as many different stones as you can (at least 5). Lay them out on a plain surface such as sand or a plain picnic rug. Feel free to add other bits and pieces that have caught your attention. Bonus points if you can name the rocks. Include this photo with your online log.
5. Take a photo of yourself, your caching name or a personal object, looking towards the south so that the sea and the beach are included. Include this photo in your online log.
Send your answers to me. Do NOT include them in your log. You do not need to wait for confirmation from me before logging this earthcache. If I don't think you have made a genuine effort to fulfill the requirements you will hear from me and if there is no response your log will be in danger of being deleted. Don't forget to include the two required photos with your log.