Destructive Plate Boundaries

Plate Tectonics and Destructive Boundaries

• Lithosphere is divided into large, rigid plates (7 major, several minor).
• Plate tectonics driven by convection currents in Earth's mantle.
• Collision of plates results in destructive/convergent plate boundaries.

Volcanic Activity: Oceanic-Oceanic Plates

• One oceanic plate subducts, melts, and forms magma.
• Magma rises, creating volcanic island arcs (e.g., Japan).
• Results in active volcanoes (e.g., Mount Fuji) with steep slopes.

Volcanic Activity: Oceanic-Continental Plates

• Oceanic plate subducts beneath continental plate.
• Magma generates volcanic eruptions along continental margin (e.g., Andes Mountains).
• Forms composite volcanoes with explosive eruptions due to high gas content.

Fold Mountains: Continental-Continental Plates

• Collision causes buckling and folding, forming mountain ranges (fold mountains).
• Example: Himalayas from Indian and Eurasian Plate collision.
• Alpine orogeny is responsible for Himalayas, Alps, and Rockies.

Orogenic Events and Fold Mountains

• Caledonian orogeny (400 million years ago): American and Eurasian plate collision formed mountains like Bluestack and Wicklow Mountains in Ireland.
• Armorican orogeny (250 million years ago): African and Eurasian plate collision created landscapes like Macgillycuddy Reeks and The Galtees in Ireland.

Summary

• Destructive plate boundaries reshape Earth's surface.
• Oceanic-oceanic and oceanic-continental collisions cause volcanic activity and island arcs.
• Continental-continental collisions lead to mountain building.