Final answer:
Cretaceous age coal is primarily found in the Great Plains region of the United States, notably in the Powder River Basin, due to the geological conditions and history conducive to coal formation during the Cretaceous period. option 3 is the correct answer.
Step-by-step explanation:
The question regards the location of the most Cretaceous age coal found today in the United States. During the Cretaceous period, the environment was ideal for coal formation, which is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers called coal beds. The locations mentioned in the options have different geological histories and ages of rock that are essential in determining where Cretaceous coal can be found.
The Appalachian Mountains are predominantly Paleozoic in age, with the rocks indicating a complex geological history of collisions and uplifts. The Rocky Mountains, on the other hand, were primarily formed during the Laramide Orogeny in the Late Cretaceous and consist of rock sediments that are significantly younger than those in the Appalachians. Moving further, the Great Plains were shaped by glacial activity and rivers, with the Cretaceous period contributing to the formative sediments that contain coal deposits. Lastly, the Pacific Coast region features active volcanic regions and is not known for substantial Cretaceous coal deposits.
When considering the age and type of rock formations necessary for coal of Cretaceous age, geologists typically point to the Powder River Basin, which is part of the Great Plains and one of the most prolific areas for coal in the United States. Thus, Cretaceous age coal is most often found in the Great Plains region of the United States.
Taking into account the geological evidence and the general consensus among scientists, the correct option for the location of the most Cretaceous age coal found today in the United States is the Great Plains.