Since the mountains' formation, forces of weathering and erosion have carved and reduced their surfaces.
(forces of weathering and erosion; have carved; T:Since the mountains' formation) (forces of weathering and erosion; reduced; their surfaces; T:Since the mountains' formation)
forces of weathering and erosion forces of weathering and erosion
have carved reduced
T:Since the mountains' formation
their surfaces T:Since the mountains' formation