Final answer:
Sorting is the term that refers to the uniformity of grain sizes in sediments, with well-sorted sediments having grains of similar size and typically indicating long-distance transport from their source.
Step-by-step explanation:
The term that refers to the uniformity of grain sizes is sorting. Sorting explains how grains of sediment are distributed by size within a rock or sediment deposit. Well-sorted sediments have grains of a similar size and typically indicate that the sediments have been transported over a long distance from their source. This process allows grains of similar sizes to settle together, creating a more uniform sediment. Poorly sorted sediments, on the other hand, have a mixture of grain sizes and are usually found closer to their source, where the energy of transport hasn't been sufficient to separate the grains by size.Sediment roundness, or the amount of smoothing of grain edges also plays a role in identifying transport history. Roundness indicates if sediment has traveled a far distance from its source, with well-rounded grains showing signs of long-distance transport.