Pohoiki Black Sand Beach is located at the Isaac Hale Park and is the newest black sand beach in Hawai'i.
This is an Earthcache and no container is placed. In order to claim the 'find', please read the description and perform the small tasks that are required. Please send the answers to me by message or email.
Beginning in May 2018 Kilauea Volcano erupted at more than twenty places along the east rift zone. Eventually Fissure Eight became the major place of origin of a massive release of lava onto the surface. The lava flow spread over lower Puna, inundating 700 homes and covering a substantial amount of land and shoreline, including Kapoho Bay.
When the flow (temperature of about 2100F) reaches the ocean, the lava is cooled quickly while the water becomes steam. It appears to be an explosive-like occurrence. As part of this interaction, the lava (which is molten, liquid rock) solidifies into many different-sized particles, from large boulders to fine-grain sand. Many of the smaller-sized particles are then transported by the ocean waves to the shore.
Begin at the coordinates and select a small portion of the black sand. Observe and evaluate the size of the grains. By referencing the Wentworth Grain Size Chart, determine the most common size of the particles. (There will be a wide range of sizes. But which size appears to be most prevalent?).
Go to Waypoint 1 at the easternmost edge of the beach. This is the wall of the lava from the recent flow. Please note that it stopped just short of entering into the park location.
At Waypoint 1, select another samll portion of sand, observe and evauate the size of the grains at this location, as you did previously at the coordinate's location. How do the size of these grains differ from the first sample?
Please send me the answers to the following questions, but DO NOT POST the answers in the log:
1. According to the Wentworth Chart, what is the prevalent grain size at the coordinates?
2. What is the prevalent grain size at Waypoint 1?
3. Do you think that the grain size will become smaller with time? If so, why?
Waypoint 2 is the upper portion of the beacon that was placed at the end of the boat ramp Breakwater structure.