Plate Tectonics and Ring of Fire

Overview

This lecture explores plate tectonics and how the distribution of earthquakes, volcanoes, and mountain ranges is linked to the movement of Earth's plates, focusing on the Pacific Ring of Fire.

Healthy Screen Habits

• Sit properly with your back supported by the chair.
• Change your sitting position regularly during long screen sessions.
• Keep dim lighting in the room to reduce eye strain.
• Stretch or walk during commercial breaks.
• Avoid watching TV in bed to prevent neck and back pain.

Plate Tectonics: Introduction and Key Features

• Plate tectonics explains Earth's surface features and movement.
• The lithosphere (crust + uppermost mantle, ~100 km thick) is broken into plates.
• The asthenosphere is a softer, solid layer beneath the lithosphere that allows plates to move.
• Convection currents in the asthenosphere drive plate movement.

Plates of the Earth

• The Earth has seven large plates: African, Antarctic, Eurasian, North American, South American, Indo-Australian, and Pacific Plate.
• The Philippine Plate is an example of a smaller plate.
• Plate boundaries are sites of significant geological activity.

Distribution of Earthquakes, Volcanoes, and Mountain Ranges

• Earthquake epicenters are mainly found in narrow zones near plate boundaries.
• Most active volcanoes are located along the edges of some continents, particularly around the Pacific Ocean.
• Mountain ranges, such as the Himalayas and Cordillera Central, are situated at or near plate boundaries.

The Pacific Ring of Fire

• The Ring of Fire surrounds the Pacific Ocean and is highly active geologically.
• About 90% of earthquakes and numerous volcanoes occur here.
• Notable volcanoes: Mount Pinatubo (Philippines), Mount Fuji (Japan), Mount St. Helens (USA).

Plate Movements and Natural Disasters

• Plate interactions cause earthquakes, volcanoes, and mountains to form.
• Earthquakes on land can be tectonic or volcanic; underwater earthquakes may cause tsunamis.
• The Philippines is particularly affected due to its location on the Ring of Fire.

Key Terms & Definitions

• Epicenter — The point on Earth's surface directly above an earthquake's focus.
• Mountain — A landform that rises prominently above its surroundings, higher than hills.
• Seismograph — An instrument that detects and records earthquake vibrations.
• Earthquake — Shaking of the Earth's surface caused by tectonic or volcanic activity.
• Volcano — An opening in Earth's crust where molten rock, ash, and gases erupt.
• Lithosphere — The solid outer shell of the Earth, including the crust and uppermost mantle.
• Asthenosphere — The semi-molten layer beneath the lithosphere that allows plate movement.
• Ring of Fire — A zone of frequent earthquakes and volcanoes encircling the Pacific Ocean.

Action Items / Next Steps

• Review your self-learning module for figures/maps on plate boundaries and distributions.
• Complete any associated enrichment activities and quizzes as indicated.
• Prepare for the next lesson on geophysical hazards in the Philippines.