Overview
This lecture covers the relationship between plate tectonics and major geological features such as mountains, rivers, ore deposits, earthquakes, and volcanoes, with global examples and explanations of their origins.
Mountain Ranges and Plate Tectonics
- Major mountain ranges (e.g., Himalayas, Andes, Rockies, Alps) are closely tied to plate tectonic processes.
- Active mountain ranges are formed by current plate collisions (e.g., Himalayas).
- Passive mountain ranges were formed by ancient collisions; evidence remains even if boundaries are inactive (e.g., Appalachians).
- Some ranges, like the Ethiopian Highlands, form at divergent (pull-apart) boundaries rather than collisions.
Geological Time and Mountain Formation
- Earth’s history is divided into Precambrian, Paleozoic, Mesozoic (age of dinosaurs), and Cenozoic (age of mammals).
- Mountain building (orogeny) events correspond to periods of plate collision throughout earth’s history.
Rivers and Drainage Basins
- River flow directions are shaped by the uplift of mountains due to tectonics.
- Major drainage basins: Mississippi (drains Rockies/Appalachians), Amazon (Andes), Congo and Nile (Ethiopian Highlands), Indus/Ganges/Yangtze (Himalayas).
- River length and watershed are influenced by the topography created by tectonic uplift.
Ore Deposits and Plate Boundaries
- Major ore deposits (gold, copper, silver, etc.) often align with plate boundaries, especially subduction zones.
- The location and richness of mineral deposits depend on the angle of subduction.
- Exploration companies use tectonic data to predict mineral locations.
Earthquakes and Plate Motions
- Most earthquakes occur along plate boundaries (convergent, divergent, and transform).
- Transform faults (e.g., San Andreas) involve plates sliding past each other, causing horizontal displacement.
- Millions of small earthquakes happen annually; strong ones are rarer but more destructive.
- Largest earthquakes are linked to subduction zones (Ring of Fire).
Volcanoes: Types and Distribution
- Volcanoes are mostly found along convergent and divergent plate boundaries (e.g., Ring of Fire).
- Some volcanoes (hotspots) occur away from plate boundaries due to mantle plumes (e.g., Hawaii, Yellowstone).
- Island arcs form at subduction zones; hotspot chains form as plates move over stationary plumes.
Key Terms & Definitions
- Orogeny — An episode of mountain building caused by plate collisions.
- Active Margin — A tectonically active plate boundary (often forming mountains/volcanoes).
- Passive Margin — An inactive or stable edge of a continental plate.
- Transform Boundary — A plate boundary where plates slide horizontally past each other.
- Hot Spot — A stationary plume of hot mantle material creating volcanoes away from plate boundaries.
Action Items / Next Steps
- Review the differences between active and passive mountain ranges.
- Prepare for a deeper study of volcanoes in the next lecture.
- Familiarize yourself with world maps of mountain ranges, river basins, earthquake, and volcano distributions.