Coe has its own volcano located near the Dowdy Ranch and Burra Burra Peak and many smaller masses (dikes) that extend as far north as the headwaters of Robison Creek. All of these bodies appear to be outliers of the Quien Sabe volcanic field located to the south of the park near Pacheco Peak. They have been dated at about 10 million years of age. The volcanic rocks that are found in the park today probably represent only a fraction of the total volcanic material that was here at one time. The volcanic rocks we see today are only the "necks" of the ancient volcanoes.