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### 17.3 Notes: Plate Boundaries - There are 3 types of plate boundaries, classified according to the type of **crust** involved. - **#1 Oceanic-Oceanic Convergent Boundary** - One oceanic plate (which is denser as a result of cooling), descends below another oceanic plate. - C...

### 17.3 Notes: Plate Boundaries - There are 3 types of plate boundaries, classified according to the type of **crust** involved. - **#1 Oceanic-Oceanic Convergent Boundary** - One oceanic plate (which is denser as a result of cooling), descends below another oceanic plate. - Characteristics: - Ocean trench where the plates meet - Row of volcanoes parallel to the trench - **#2 Oceanic-Continental Convergent Boundary** - Oceanic crust is denser than continental crust, so when the 2 types of crust converge, oceanic crust is **subducted** under the less-dense continental crust. - Characteristics: A trench and a volcanic **mountain range** near the coast. (i.e. Mt St Helens in the Cascade Mountains on the US Pacific Coast) - **#3 Continental-Continental Convergent Boundary** - These form when 2 continental plates **collide** and one is **pushed** under the other.