Overview
This lecture covered healthy screen habits and the basics of plate tectonics, focusing on how earthquake epicenters, volcanoes, and mountain ranges are distributed on Earth.
Healthy Screen Habits
- Sit with your back supported by the chair backrest.
- Change your sitting position regularly during long viewing periods.
- Use dim lighting in the room to protect your eyes.
- Stretch or walk during breaks to avoid stiffness.
- Avoid watching TV in bed to prevent neck and back pain.
Introduction to Plate Tectonics
- Plate tectonics explains Earth’s surface features and movement in the past and present.
- The lithosphere is a 100 km thick solid layer made of crust and upper mantle.
- The asthenosphere lies below the lithosphere, is softer, and enables plate movement.
- Convection in the asthenosphere drives plate movements.
Earth's Plates and Their Movements
- The lithosphere is broken into large and small plates, including the Philippine Plate.
- Seven major plates: African, Antarctic, Eurasian, North American, South American, Indo-Australian, and Pacific.
- Plate movements cause earthquakes, volcanoes, and mountain formations.
Distribution of Earthquakes, Volcanoes, and Mountains
- Earthquake epicenters are concentrated in narrow zones, often at plate boundaries.
- Active volcanoes are mostly along the edges of continents, especially around the Pacific.
- Major mountain ranges are formed at plate boundaries (e.g., Himalayas, Cordillera Central, Sierra Madre).
Pacific Ring of Fire
- The Ring of Fire surrounds the Pacific Ocean and is highly active geologically.
- 90% of the world’s earthquakes and many volcanoes occur here.
- The Philippines is within the Ring of Fire, making it prone to natural hazards.
Notable Features and Examples
- Mount Pinatubo (Philippines) had a major eruption in 1991.
- Mount Fuji (Japan) and Mount St. Helens (USA) are significant active volcanoes.
- Sierra Madre is the longest mountain range in the Philippines.
Key Terms & Definitions
- Epicenter — The point on Earth’s surface directly above an earthquake’s focus.
- Mountain — A landform with steep slopes, higher than a hill.
- Seismograph — An instrument measuring earthquake vibrations.
- Earthquake — Sudden shaking of Earth from tectonic or volcanic activity.
- Volcano — An opening in Earth’s crust where lava, ash, and gases erupt.
- Lithosphere — Earth’s rigid outer layer (crust and upper mantle).
- Asthenosphere — Softer layer beneath the lithosphere enabling plate movement.
- Ring of Fire — A zone of frequent earthquakes and volcanoes around the Pacific Ocean.
Action Items / Next Steps
- Review figures and maps in your self-learning module on plate tectonics.
- Prepare for next session: focus on areas in the Philippines vulnerable to geophysical hazards.