Answer:
Dana filtered the sample and larger granules of the sample were left behind.
Explanation:
If a substance is pure, it will have a uniform composition throughout. It will not separate into particles of various sizes.
One of the characteristics of pure substances is that they are homogeneous. A mixture is definitely made up of particles of various sizes.
Since the particles was filtered and larger granules were left behind, the sample has been separated by a physical method (filtration). Only a mixture can be separated by physical methods. It is not a pure substance.
I don’t really have a clear answer for you but this might help
Often, the rock layers bookending the mass extinction are noticeably different in their compositions. These changes in the rocks show the effects of environmental disturbances that triggered the mass extinction and sometimes hint at the catastrophic cause of the extinction
