Intro (Micro Notes):
• Circum-Pacific zone = “Pacific Ring of Fire”
• Tectonically active belt around Pacific Ocean basin
• Extends through western Americas, East Asia, SE Asia, Oceania
Key Geophysical Characteristics:
1. Plate Boundaries:
• Convergent (subduction zones) – Nazca, Pacific, Philippine, Cocos plates
• Major trench systems: Mariana Trench, Peru-Chile Trench, Japan Trench
2. Volcanism:
• ~75% of world’s active/dormant volcanoes
• Major volcanoes: Mt. Fuji (Japan), Mt. St. Helens (USA), Mt. Mayon (Philippines)
3. Seismic Activity:
• ~90% of world’s earthquakes occur here
• Earthquake zones: Japan, Chile, California, Indonesia
• Tsunami-prone – e.g., 2004 Indian Ocean Tsunami, 2011 Japan Tsunami
4. Mountain Building (Orogeny):
• Andes (South America), Rockies (North America), Japanese Alps
• Caused by ongoing tectonic collisions
5. Island Arcs and Hotspots:
• Japan, Philippines, Indonesia – island arcs from subduction
• Hawaii – formed via mid-plate hotspot volcanism
Conclusion (Micro Notes):
• Circum-Pacific = most geodynamically active zone globally
• Shaped by tectonic collisions, subductions, volcanism, and seismicity
• High risk zone, critical for disaster management, seismology, and global geophysical studies