Sand and gravel have second economic value when it comes to ocean. Sand is used in various types pf activities as it is used for decorative purposes, construction processes and at many other places.
Gravels are small stones that is used as decorative material inside aquariums and it is also used in homes and hotels as a source of decoration and construction.
It has a bit low value as compare to oil that is extracted from ocean.
Due to mutations in DNA that accumulate at a fairly constant rate , the reduction in melting temperature for hybrid DNA between two mammalian species, it is used to predict how long those species have been since divergence.
