Final answer:
The Rio Grande riverbed was shaped by erosion from the Rocky Mountains, geological events such as the Laramide Orogeny, and the impact of fault movement, with influences from the shaping power of glaciers and rivers over time.
Step-by-step explanation:
The Rio Grande riverbed was most likely created through a combination of geological processes, including the erosion of material from the Rocky Mountains and the subsequent shaping by glaciers and rivers. Over time, the region has been influenced by different geological events such as the Laramide Orogeny, which occurred between 50 to 70 million years ago. This event played a significant role in the uplift and formation of mountain ranges in western North America, which ultimately contributed to the shaping of the riverbeds.
The movement along faults during this period, as seen in parts of the Great Plains, also affected the terrain. Furthermore, sedimentary rocks were deposited and then eroded by rivers like the Rio Grande, leading to the creation of its riverbed. The presence of mudcracks and the evidence of intense tropical weathering in different regions indicate that climatic factors and river activities have been shaping the landscape over millions of years, reinforcing the riverbed's formation through natural erosion processes.