The other half of the missing plate motion has disappeared in the Basin and Range geologic province east of the San Andreas, the geologists say.
The rotating mountains, the extending Basin and Range, and the observed San Andreas motion together explain the entire motion between the Pacific and North American plates.
The latest blow to the textbook account comes from an analysis of fossil leaves in Nevada's Basin and Range geologic province, which separates the Sierra Nevada from the Rocky Mountains and the Colorado Plateau.
Because moisture and temperature control these features, Wolfe and his colleagues could use the fossils to determine earlier climatic conditions of the Basin and Range.
According to the new study, reported in the June 13 Science, the Basin and Range reached some 3,000 meters above sea level 16 million years ago, then dropped to its present height by about 13 million years ago.
Presumably, in the long run, places like the Andes will show the same sort of pattern as the Basin and Range," he says.
The Basin and Range province, as all geology students learn, is an area of the western United States predominantly Nevada and western Utah - that plate-tectonic forces have stretched and thinned, producing a distinctive landscape that lives up to its name.
Jorge ArandaGomez of the Universidad Nacional Autonoma de Mexico in Guanajuato present evidence that much of northern and central Mexico was stretched at the same time as regions in the United States and therefore constitutes part of the Basin and Range.