Sand Origins Lab

When we go to the beach, the only thing we tend to want to do is lay down our towel, get out the tanning lotion, and relax for a full day of tanning, surf, and sun. But what few people wonder or care about is where the beach came from, where it's going in the future, or what it's made out of. (Probably be better not to tell them anyway, there's a good chance they are laying on parrot fish poop anyway)

There are two different types of beaches. Detrital beaches are formed from rock or other material that was never alive. Biogenic beaches come from things that used to be alive, such as coral. We will be testing sand with vinegar for the presence of calcium carbonate. Calcium carbonate is found in alive or once alive particles.

Question: Which beaches originate from rock and which ones originate from life?

Hypothesis: I think that Big Beach will be a biogenic beach, while Oneuli (black sand beach) will be detrital.

Materials: Vinegar, pipette, sand, and a jar or cup to hold the sand in.

Procedure: After collecting sand samples from the two beaches, we will bring them back to lab and test to see if they contain calcium carbonate. We will be doing this by pouring 20 drops of vinegar in the sand sample. If it bubbles and makes a popping sound, it has calcium carbonate in it.

~Update~

Conclusion: Results from the lab test were a little different than my hypothesis, but not at surprising to me. My hypothesis was that Big Beach would be biogenic, while Black Sand would be I was sure that the black sand beach would be detrital, and even though it was(partly), it also had some biogenic materials in it as well. there was also some biogenic material in there as well. Big Beach was a biogenic beach as I predicted. The results and observations from the lab were:

Big Beach: The beach is big and is mostly a tannish color with some debris sprinkled in from the surrounding trees and other plants. Big offshore reef. Some lava rock is in the area, but does not contribute to sand or sand color. The results from the test were that there was sufficient crackling and popping. The beach is biogenic.

Oneuli (Black sand): The color of Oneuli is reddish black. It is right up next to a cinder cone hill which feeds the beach. Some offshore reefs can be found. There was some crackling when vinegar was added, but the only conclusion that can be drawn is that there is a combination of detrital and biogenic sand there.

Possible sources of error could include the lack of sand that we tested. Maybe it would have been different if we had tested different parts of the beach. Other sources of error could be we had traces of plants in our sand samples, which could add to the crackling.

Overall, it was a fun experience and a great way to explore the beaches that are in our own background.

Picture from Big Beach: The sand from Big Beach appears biogenic because of its color and the offshore reefs, but as this photo shows lava rock is not scarce in the area.