This view is from the floor of Wooden Valley, east of Napa, looking west at the scarp created by the Green Valley fault. Stop 3 is on the horizon near the left edge. The Green Valley fault is part of the San Andreas fault system, a continuation of the Concord fault. Its mapped trace ends here in a zone of extensive landslides (the fresh debris flow is shown close up in the landslides gallery). The San Andreas fault system has sliced apart the former subduction zone at an angle and carried pieces of it to the north since the Miocene, about 12 million years ago. Lava flows of the Sonoma Volcanics (61 Ma) top the ridge.