Final answer:
Diatomaceous earth accumulates above the CCD due to its resistance to dissolution in less corrosive upper ocean layers and dissolves below the CCD where the water is more acidic.
Step-by-step explanation:
Diatomaceous earth, which is composed of silica, accumulates above the CCD (Carbonate Compensation Depth) and dissolves below the CCD. This is because diatom frustules, which are high in silica (silica dioxide), are more resistant to dissolution in the upper layers of the ocean where the water is less corrosive. However, below the CCD, the acidity of the water increases, leading to the dissolution of silica-based frustules.
Above the CCD, the remains of diatoms accumulate on the ocean floor, forming sedimentary deposits known as diatomite, which can also be used as a mechanical insecticide or in products like dynamite. These layers of diatomite are a result of diatom population blooms during periods of nutrient availability when their numbers exceed what can be consumed by aquatic organisms.