Hidden Treasure EarthCache
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EXTREME CAUTION IS REQUIRED HERE - NOTE THE TERRAIN RATING
THERE ARE STEEP STEPS THAT REQUIRE CARE ESPECIALLY WHEN WET
The beach here is a special little world of it’s own, winding down stone steps carved into the cliff, you will see a large variety of different coloured rocks. The rocks here are pre-dominantly sedimentary rocks.
Sedimentary Rock: Sedimentary rocks are formed by sediment that is deposited over time, usually as layers at the bottom of lakes and oceans. This sediment can include minerals, small pieces of plants and other organic matter. The sediment is compressed over a long period of time before consolidating into solid layers of rock. The sedimentary rock cover of the continents of the Earth's crust is extensive, but the total contribution of sedimentary rocks is estimated to be only 8% of the total volume of the crust.The study of sedimentary rocks and rock strata provides information about the subsurface that is useful for civil engineering, for example in the construction of roads, houses, tunnels, canals or other structures. Sedimentary rocks are also important sources of natural resources like coal, fossil fuels, drinking water or ores.
Limestone and Sandstone make up most of the sedimentary rocks on the planet
- Limestone: Composed primarily of calcium carbonate. It can form organically from the accumulation of shell, coral, algal and fecal debris. It can also form chemically from the precipitation of calcium carbonate from lake or ocean water.
- Sandstone: Composed primarily of grain sized sediments from weathering debris (1/16 to 2 millimeter diameter).
Other kinds are important too:
- Coal is a sedimentary rock made from accumulated plants.
- Conglomerate is a sedimentary rock that resembles concrete because it is made from pebbles, like those you see on a stony beach.
- Rock salt is an unusual sedimentary rock made entirely of salt (sodium chloride) that is left behind when seawater dries up completely.
Sedimentary rocks can have a wide range of colours:
- WHITE: Limestone and sandstone in their original “pure” state are white or cream.
- GREY: If limestone and sandstone contain mud they are grey.
- RED: Rocks which are red contain a red iron oxide mineral called hematite. The rock turns the color red because of oxidization which occurs when organic material is deposited in moving water with the presence of oxygen, turning it to carbon dioxide and water. The iron will change in composition turning the remains a deep red or rusty color.
- GREEN: Rocks which are green may contain the green mineral chlorite or come from an environment low in, or lacking, oxygen, often associated with marine environments.
- BLACK: Rocks which are black such as mudstone contains a lot of carbon (from the remains of organic materials such as plants).
- YELLOW: Rocks which are yellow such as shale contains limonite or goethite which is found in low-temperature environments.
To log your visit please send me the answers to the following:
1a) What unusual colour rock is predominantly seen here on the beach?
1b) Using the guide above identify why it is this colour?
2) What height is the largest boulder on the beach?
3) How many steps did you walk down to get to the beach?
You may log your find when you have sent me the answers. I will let you know if they are not correct. If I do not receive any answers within 2 weeks, your log will be deleted.
Whilst I'd love to see photos with your answers, please don't post any spoilers on the cache page itself as these will be deleted. (Photos with the sea in the background are ok).
Interesting non-geological fact: Pirate's Cove got it's name locally from the great Pirate Queen Grace O'Malley who on her way to Dublin, stopped off at this very cove and had her pirates working by torch light to hack and cut the steps from the rocky cliff face, to allow their pirate queen ascend to Howth's summit undetected by the English. Grace tried to call upon Lord Howth at his castle only to be informed the family was at dinner and she was not a welcome guest. This rejection did not sit well with the fierce Grace and the Lord of Howth soon felt the full brunt of the pirate queen's wrath when she abducted his grandson and heir. The terms of the child's release included a promise from Lord Howth to keep the gates of his castle open to unexpected visitors, and to always set an extra place at every meal. This pledge is still honored at Howth Castle to this very day, with an extra place setting laid at the table.
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