Final answer:
Yellow dunes and grey dunes differ in their stages of development, vegetation cover, and soil characteristics; yellow dunes are younger and less vegetated, whereas grey dunes are older with more varied vegetation and developed soil.
Step-by-step explanation:
Apart from their color, yellow dunes and grey dunes primarily differ in their respective stages of development, vegetation cover, and soil characteristics. Yellow dunes are younger, forming near the shoreline where the sand is continually being deposited. These dunes typically have little vegetation, mainly pioneer plants like marram grass that can withstand the harsh, shifting conditions and help stabilize the dune. In contrast, grey dunes are older and more stable; they are found further inland and have a more established layer of humus from continued plant decay, giving them a greyer color. The vegetation on grey dunes is more varied and dense, with a wider array of species, including shrubs and bushes, as well as evidence of soil development.
The presence of cross-bedding in the geological record, as highlighted in Figure 4.7 from Coyote Gulch, illustrates how ancient sand dunes, which may have once been yellow dunes, become compacted and solidified into rock formations, with striations indicating different periods of sand deposition. These ancient dunes, through processes of soil evolution and changes in the ecosystem, give us insight into how yellow dunes can transform into grey dunes over time.