In the image above, click the green right arrow to go forward and the red left arrow to go back in time. When going forward, the old land surface rises up as a black outline, showing how much erosion is occuring. A large orange arrow indicates the tectonic uplift (change in forces supporting the range, as opposed to uplift in response to erosion). The color bars in the mountains are each about 1 km thick. The reddish solid line indicates the mean elevation.
The "traditional" history of the Sierra starts with much of the erosion of the old Mesozoic volcanic arc having ended by the Eocene, when fairly low relief existed across most of the Sierra. Over the bulk of the Cenozoic, some erosion occurs in the southern Sierra, here shown to match apatite He diffusion ages in the southern Sierra (though some of that erosion is older in a more fully traditional model). At 10 Ma, a volcanic flow fills the river channel (shown as an orange body). This channel is now about 1 km above the modern channel, a relationship shown as the orange body rises up during erosion.
This cartoon illustrates the evolution of an area in the vicinity of the modern San Joaquin River. This interpretation is in conflict with He-diffusion dates from constant-elevation tranverses in the southern Sierra, if the interpretation of those dates as evidence of paleotopography is correct.