Geology of Bermuda:
Bermuda is a volcanic sea mountain that formed from the mid-Atlantic ridge approximately 100 million years ago. Through the processes of plate tectonics and seafloor spreading, this volcano moved to the west of the mid-Atlantic ridge and became extinct. About 30 million years ago, the volcano erupted again, probably due to it floating over a hot spot in the Earth's crust. Afterward, the volcano became extinct again and has remained so to this day. Over the millions of years, a limestone cap has formed on top of the volcanic rock. When one looks at the natural terrain today, only the limestone cap is visible. In Horseshoe Bay, one can clearly observe the large limestone rock formations along the sides of the beach. This earthcache will largely deal with these large rock formations.
What is Weathering?
Weathering is the breaking down of rocks, soil, and minerals as well as wood and artificial materials through contact with the Earth's atmosphere, water, and biological organisms. Weathering occurs on-site, that is, in the same place, with little or no movement, and thus should not be confused with erosion, which involves the movement of rocks and minerals by agents such as water, ice, snow, wind, waves and gravity and then being transported and deposited in other locations.
What is Salt-Crystal Weathering?
Salt crystallization causes the disintegration of rocks when saline solutions seep into cracks and joints in the rocks and evaporate, leaving salt crystals behind. These salt crystals expand as they are heated up, exerting pressure on the confining rock. Salt crystallization may also take place when solutions decompose rocks (for example, limestone and chalk) to form salt solutions of sodium sulfate or sodium carbonate, of which the moisture evaporates to form their respective salt crystals. The salts which have proved most effective in disintegrating rocks are sodium sulfate, magnesium sulfate, and calcium chloride. Some of these salts can expand up to three times or even more. Salt crystallization is normally associated with arid climates where strong heating causes strong evaporation and therefore salt crystallization. It is also common along coasts.
Logging Requirements:
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At the GZ, look for some examples of salt-crystal weathering in the rock structures. You may search the formations both on the beach and in the cove. Estimate the size of the eroded portions in the rock.
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Why does salt-crystal weathering occur in Horseshoe Bay? Provide evidence that you see at the GZ and from the description to back up your claim.
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As of June 2019, earthcaches are now allowed to have a required photo logging task. Please provide a photo of yourself, your GPSr, or a personal item that proves that you have visited this site. Please post this in your log.
**Please use caution around the rock formations!**
**Confirm your find by answering these questions on this Google Form or by sending your answers to us via message center**
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Sources:
http://www.elbowbeachcycles.bm/bermuda-geological-history/
http://www.coexploration.org/projects/heidi/naturalhistory.htm
https://en.wikipedia.org/wiki/Weathering
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