For your information: this EarthCache is one of three here in 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: There's Green Sand Too!
What is Pāhoehoe lava?
Pāhoehoe is basaltic lava that has a smooth, billowy, undulating, or ropy surface. These surface features are due to the movement of very fluid lava under a congealing surface crust. The Hawaiian word was introduced as a technical term in geology by Clarence Dutton. A pāhoehoe flow typically advances as a series of small lobes and toes that continually break out from a cooled crust. It also forms lava tubes where the minimal heat loss maintains low viscosity. The surface texture of pāhoehoe flows varies widely, displaying all kinds of bizarre shapes often referred to as lava sculpture. With increasing distance from the source, pāhoehoe flows may change into ʻaʻā flows in response to heat loss and consequent increase in viscosity.
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 (they should look like little divots).
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Go to the waypoint (located at 19.735917, -155.013580). From the lookout, observe the chunks of pahoehoe lava near the ocean. Describe the appearance of the lava.
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Why does salt-crystal weathering occur at Richardson? 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!**
Congrats to Skotlee and gwon3 for the FTF!
Enjoyed finding this EarthCache? Consider awarding it a favorite point!
Sources:
https://www.britannica.com/science/lava-volcanic-ejecta#ref11633
http://www.coexploration.org/projects/heidi/naturalhistory.htm
https://en.wikipedia.org/wiki/Weathering
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