incorporated into proto-North America by the middle of the Triassic, some of them finding their way to the area of the park. Most of these igneous and sedimentary rocks have since been heavily metamorphosed, uplifted and eroded away. Outcrops of the resulting Shoo Fly Complex (made of schists and gneisses) and younger Calaveras Complex (a mélange of shale, siltstone, and chert with mafic inclusions) are now found in the western side of the park. Later volcanism in the Jurassic intruded and covered these rocks in what may have been magmatic activity associated with the early stages of the creation of the Sierra Nevada Batholith. 95% of these rocks were eventually removed by uplifted-accelerated erosion. Most of the remaining rocks are exposed as 'roof pendants' in the eastern metamorphic zone. Mount Dana and Mount Gibbs are made of these metavolcanic rocks. Only 5% of the rocks exposed in Yosemite National Park are metamorphic. Pluton emplacement The first phase of regional plutonism started 210 million years ago in the late Triassic and continued throughout the Jurassic to about 150 million years BP. Also starting 150 million years ago was an increase in the westward drift rate of the North American Plate. The resulting orogeny (mountain-building event) is called the Nevadan orogeny by geologists. The resulting Nevadan mountain range (also called the Ancestral Sierra Nevada) was 15,000 feet (4500 m) high and was made of sections of seafloor and mélange. These rocks were later metamorphosed and today can be seen in the gold-bearing metamorphic belt of California's Mother Lode country. In the area of the park these rocks are exposed along the Merced River and State Route 140. This was directly part of the creation of the Sierra Nevada Batholith, and the resulting rocks were mostly granitic in composition and emplaced about 6 miles (10 km) below the surface. The second, major pluton emplacement phase lasted from about 120 million to 80 million years ago during the Cretaceous. This was part of the Sevier orogeny. All told there have been more than 50 plutons found in the park. A few miles (several km) of material was eroded away, leaving the Nevadan mountains as a long series of hills a few hundred feet (tens of meters) high by 25 million years ago. Cenozoic activity Volcanism Starting 20 million years ago and lasting until 5 million years ago a now-extinct extension of Cascade Range volcanoes