• A plate boundary is where the A plate boundary is where the edges of two plates meet.edges of two plates meet.

• There are 3 types of boundaries:There are 3 types of boundaries:1.1. Divergent Divergent 2.2. ConvergentConvergent3.3. TransformTransform

• Occur where plates move apart. Occur where plates move apart. Most divergent boundaries are Most divergent boundaries are found in the ocean.found in the ocean.

• In the ocean, In the ocean, divergentdivergent boundaries boundaries are also called are also called spreading centersspreading centers..

• Mid-ocean ridgesMid-ocean ridges mark the sites mark the sites where the ocean floor is where the ocean floor is spreadingspreading apart.apart.

• As the ridges continue to widen, a As the ridges continue to widen, a gap called a gap called a rift valleyrift valley forms. forms.

• Occur where plates push together.Occur where plates push together.• There are 3 types of There are 3 types of convergentconvergent

plate boundaries.plate boundaries.

1.1. Continental-continental collision:Continental-continental collision:– Occurs where 2 plates carrying Occurs where 2 plates carrying

continental crust (same density) continental crust (same density) push together.push together.

– If the plates keep moving, their If the plates keep moving, their edges crumple and fold.edges crumple and fold.

2. Oceanic-oceanic subduction:2. Oceanic-oceanic subduction:–Occurs where one plate with Occurs where one plate with

oceanic crust sinks, or subducts, oceanic crust sinks, or subducts, under another plate with oceanic under another plate with oceanic crust.crust.–Deep-ocean trenches and island Deep-ocean trenches and island

arcs form.arcs form.

3. Oceanic-continental subduction:3. Oceanic-continental subduction:–Occurs when ocean crust sinks Occurs when ocean crust sinks

under continental crust.under continental crust.–Deep-ocean trenches and coastal Deep-ocean trenches and coastal

mountains form.mountains form.

• Occur where plates scrape past Occur where plates scrape past each other in opposite directions.each other in opposite directions.

• Occur where plates scrape past Occur where plates scrape past each other in opposite directions.each other in opposite directions.

• Occur where plates scrape past Occur where plates scrape past each other in opposite directions.each other in opposite directions.