Other
Ocean Trenches
A rather detailed explanation of how trenches form and why. No graphics, but some interesting explanations as well as links to other sites and extensive reference list.
CK-12 Foundation
Ck 12: Earth Science: Earthquakes at Convergent Plate Boundaries
[Free Registration/Login may be required to access all resource tools.] How and why convergent plate boundaries cause massive earthquakes.
CK-12 Foundation
Ck 12: Earth Science: Volcanoes at Plate Boundaries
[Free Registration/Login may be required to access all resource tools.] Volcanoes most often occur at plate boundaries.