For your information: this EarthCache is one of three in here Richardson Ocean Park. It is not required to find all three, but they share similar geoscience lessons on lava and sediment formation. The other two EarthCaches (within just feet of this geocache) are:
ROP: Black Sand Beach
ROP: Salt-Crystal Weathering
Sand:
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Sand is divided into five categories based on its size:
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Very fine sand (1/16 – 1/8mm)
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Fine sand (1/8 – 1/4mm)
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Medium sand (1/4mm – 1/2mm)
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Coarse sand (1/2mm – 1mm)
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Very coarse sand (1 mm – 2mm)
These are accurate measurements according to the Udden-Wentworth Scale
Why is green sand, green?
Green sand beaches get their names from the green glassy crystals (Olivine) that make up most of the sand on this beach. Olivine is locally known as “Hawaiian Diamond” and is denser and tougher than the ash fragments, glass, and black pyroxene that make up the rest of the volcanic material at the beach. Olivine is relatively heavy and tends to accumulate on the beach, whereas the lighter volcanic sand is swept out to sea.
How green do green sand beaches get?
How “green” the sand on a beach is, depends on the two following factors:
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Chemical composition: Most green sand beaches have different shades of green, depending on the minerals that give them their color. Some examples of these ‘green’ minerals are: Glauconite, Malachite, Chlorite, Epidote, and Serpentine. In Richardson Ocean Park, the mineral that gives some of the sand a gree hue is olivine.
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Amount of olivine: Olivine is a pretty common constituent of basalt (lava), and it can be found all over the Big Island and in many other volcanic regions in the world.
Logging Tasks:
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Pick up a handful of sand at the GZ and observe it. Based on your observations, does the sand at Richardson Ocean Park contain:
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a) 10-20% green sand
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b) 20-40% green sand
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How does Richardson Beach’s black sand compare to its green sand? Is there a difference in size, color, texture, etc?
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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.
Congrats to Skotlee and gwon3 for the FTF!
Enjoyed finding this EarthCache? Consider awarding it a favorite point!
Sources:
https://www.lovebigisland.com/quick-and-remarkable-facts-about-hawaii/green-sand-beach/
https://www.lovebigisland.com/big-island-beaches/richardsons/
https://en.wikipedia.org/wiki/Olivine#Crystal_structure
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