Overview
The lecture covers healthy screen habits and introduces plate tectonics, focusing on the global distribution of earthquakes, volcanoes, and mountain ranges, with examples from the Philippines and around the Pacific Ring of Fire.
Healthy Screen Habits
- Sit properly with your back supported by the chair’s backrest.
- Change your sitting position regularly during long screen sessions.
- Keep dim lighting in the room to protect your eyes.
- Use breaks to stretch, move around, or change posture.
- Avoid watching TV in bed to prevent neck and back pain.
Introduction to Plate Tectonics
- Plate tectonics explains Earth's surface features and movements, both past and present.
- The lithosphere is a ~100 km thick solid layer comprising the crust and upper mantle.
- Beneath the lithosphere is the asthenosphere; solid but softer, allowing convection currents.
- The Earth's lithosphere is broken into large and small plates.
Plate Movements and Earth's Features
- There are seven major plates: African, Antarctic, Eurasian, North American, South American, Indo-Australian, and Pacific plates.
- Plate movements result in earthquakes, volcanism, and mountain formation.
- Earthquakes, volcanoes, and mountain ranges are often located near plate boundaries.
Distribution of Earthquakes, Volcanoes, and Mountain Ranges
- Earthquakes are concentrated in narrow zones, often near plate boundaries, not randomly distributed.
- Most volcanoes are found along continental edges, especially around the Pacific.
- Major mountain ranges include the Himalayas (world’s highest), Cordillera Central, and Sierra Madre (longest in the Philippines).
The Pacific Ring of Fire
- The Ring of Fire (Circum-Pacific Belt) is a geologically active region with frequent earthquakes and volcanic eruptions.
- Around 90% of the world's earthquakes occur in the Ring of Fire.
- Notable volcanoes: Mount Pinatubo in the Philippines, Mount Fuji in Japan, and Mount St. Helens in the USA.
Key Terms & Definitions
- Epicenter — The point on Earth's surface directly above the focus of an earthquake.
- Mountain — A landmass rising higher than the surrounding area, with higher elevation than a hill.
- Seismograph — An instrument that detects and records earthquake vibrations.
- Earthquake — Sudden shaking of the ground, usually caused by tectonic or volcanic activity.
- Volcano — An opening in Earth's crust through which lava, ash, and gases erupt.
Action Items / Next Steps
- Review your self-learning module and observe distributed maps of earthquakes, volcanoes, and mountain ranges.
- Prepare for the next lesson on geophysical hazards and areas prone to natural phenomena in the Philippines.