Theory of Continental Drift

Three Types of Plate Boundaries:

• Divergent—Boundary where plates move apart (ex: Great Rift Valley—Africa; Mid ocean Ridges)
• Convergent—Boundary where plates come together (ex: Himalayan mountains, Alps)
• Transform—Boundary where two plates slide along side each other (ex: San Andreas Fault—San Francisco)

• Convergent Boundaries form when two
• tectonic plates come towards each other.
• There are three types of convergent boundaries
• or destructive boundaries.
• **continent - continent
• **ocean – ocean
• **continent – ocean

• Continent -Continent: Mountains form and earthquakes occur when continental plates run into each other and fold upwards. (Ex: Himalayas and Alps)

• Continent to continent

• The summit of Mt. Everest
• is made of marine limestone.

• Ocean Plate-Ocean Plate: Volcanic island arcs, trenches & earthquakes occur when older ocean plate subducts under a younger ocean plate.
• (Ex: Japan, Aleutian Islands-off Alaska, Philippines, Tonga Islands, Marianas Trench).
•    

• Ocean to Ocean Boundary

• Earth Observatory Center: Japan

• Ocean Plate-Continent Plate: Mountains, volcanoes and earthquakes occur as an ocean plate subducts under a continental plate. The Oceanic plate melts; less dense-magma rises to form volcanoes. (Ex: Andes, Cascade Range, Sierra Nevada)

• Ocean to Continent Boundary

• Goddard Space Flight Center

• Ocean to Ocean and Ocean to continent are destructive boundaries