Convergent boundaries

Ocean/Ocean Convergent Boundary 

Two oceanic plates are moving towards one another, characterized by a subduction zone.

One of the plates sinks or subducts below the other. The subducting plate begins to melt at approximately 700km producing a magma that results in volcanic activity.  

Geographic features: Deep ocean trench, volcanic island arc

Geologic Effects: Deep focus earthquakes, explosive volcanism

Example:  Philippine Islands or the Mariana Trench

Link to Mariana Trench dive animation 

Ocean/Continent Convergent Boundary 

An ocean and a continental plate are moving towards each other, characterized by a subduction zone offshore of the coastline. The ocean plate ALWAYS subducts under the continental plate.

Geographic Features: Deep ocean trench offshore of the continent, volcanic mountain range inland from the coast

Geologic Effects: Deep focus earthquakes and explosive volcanism

Example: Cascade Range (Mt. St. Helens)

Continent/Continent Convergent Boundary 

No subduction occurs because both plates are composed of less dense continental material.

Geographic Features: Extremely high (non-volcanic) mountains

Geologic Effects: Intense earthquake activity accompanies extreme deformation of rock material, NO volcanism  

Example: Himalayas