Where is the Sand From?

Sandy beaches are everyone's favorite. Where does the sand come from? There are two types. Biogenic sand comes from something once living (shells, exoskeletons, coral). Detrital sand comes from rock that's eroded To assess our data from given beaches, we will test our sand using vinegar to find out if it contains calcium carbonate (which will create a bubbling reaction if it's biogenic).

vinegar  + calcium carbonate = calcium acetate + water + carbon dioxide (the bubble effect)

Less popularly known as: 2CH3COOH + CaCO3 = Ca(CH3COO)2 + H2O + CO2

Question: Which beaches on south Maui (Kihei area) will turn out to be biogenic, and which will be detrital?


Hypothesis: I predict that Big beach will be a biogenic beach, and black sand beach will be primarily detrital.
If the sand reacts to the vinegar, it will be biogenic, and otherwise detrital.


Materials: Journal, pen, cup (for sand), vinegar, pipette, map, and sand.

Procedure:
1. Gather materials
2. Make observations of chosen beaches
3. Collect sand from chosen beaches
4. Test the sand with vinegar using 20 drops from the pipette
5. Record your data after determining it's origin

    Makena Beach (Onelua)

   

    Black Sand Beach

Makena Beach: This beach is long, and white, with fine sand and Keawe shade. There is a dead reef offshore, which produces sand, and harbors the coast from much erosion.

Black Sand Beach: This beach is hidden, and often shaded by trees and high rock that surrounds it. It has grainy salt and pepper sand. The surrounding rock seems like it has eroded a lot, producing sand for this beach.

Data: Big beach's sample bubbled the most of any sample we tested, with lots of popping, which means it's a biogenic beach. Black Sand beach made no bubbling, with slight popping, and it's results suggested it was detrital.

Conclusion: The purpose of this lab was to find whether certain beaches on south Maui were biogenic or detrital. After testing our samples, we found that Black Sand beach was primarily detrital, and Big beach was biogenic. The results from our sampling matched my hypothesis almost exactly.

Possible Sources of Error:

•  failed to observe certain reefs, cliffs, or other factors
• added the wrong amount of vinegar to our samples
• mislabeled our sand samples
• recorded our data incorrectly