Next figure-- Previous figure-- Table of Contents-- Pacific Northwest Earthquakes

---

Figure 10. Three types of plate boundaries. A spreading boundary (a) marks the divergence of two plates. Material welling up from the mantle creates a rise or ri dge bordering the rift between separating plates. A convergent boundary (b) occurs where one plate moves t owards another. If one of these plates slides beneath the other, the motion is called subduction. A tra nsform boundary (c) occurs where relative plate motion is neither divergent or convergent, but is parallel to the plate edges. The geometry of plates off the coast of Washington is schematically shown in this figur e; plate locations are shown in Fig. 8.

---

Next figure-- Previous figure-- Table of Contents-- Pacific Northwest Earthquakes

---