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 evolution of the Sierra as envisioned by House et al with an intermediate step at 10 Ma. Topography about 50 Ma from variation in He diffusion ages along a constant-elevation transect in the western Sierra interpreted as an effect of high relief. Total erosion matched to that inferred from the He closure temperatures. At 10 Ma, a volcanic flow fills the highest 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. No tectonic uplift in the past 10 My was assumed.
This cartoon illustrates the evolution of an area in the vicinity of the modern San Joaquin River. It violates measurements of erosion rates over the past few thousands of years in the uplands, and violates the greater erosion in streams than uplands that have also been found, but all of these numbers are for the Holocene or latest Pleistocene. Such incredible relief in the early Cenozoic seems difficult to reconcile with the low relief surface under the Eocene sediments of the northern Sierra.