Overview
This lecture covers the main processes that shape the earth’s landforms, focusing on internal (endogenic) and external (exogenic) forces, with examples like volcanoes, earthquakes, rivers, sea waves, glaciers, and wind.
Classification of Earth’s Forces
- Endogenic forces originate from within the Earth and cause changes like mountain formation, volcanoes, and earthquakes.
- Exogenic forces originate outside the Earth, including wind, water, rain, sea waves, and glaciers.
- Exogenic changes can be erosional (wearing away) or depositional (building up).
Endogenic Processes: Volcanoes and Earthquakes
- Volcanoes occur when magma escapes through a vent; the material that erupts is called lava.
- Important volcanic features: vent (opening), crater (upper depression), caldera (large crater), magma chamber (source).
- Earthquakes originate at a focus below Earth’s surface; the epicenter is the point above it on the surface.
- Earthquake waves: P waves (longitudinal), S waves (transverse), L waves (surface).
- Richter scale measures earthquake intensity; each unit increase means 10 times stronger.
- Earthquake safety: stay near walls, corners, under tables, and away from fires.
Weathering vs. Erosion
- Weathering: breaking of rocks into smaller pieces in place.
- Erosion: movement of rock fragments by wind, water, or glaciers to new locations.
Exogenic Processes: River Action
- Rivers create features in youth (waterfalls, meanders), maturity (flood plains, levees), and old age (deltas).
- Waterfall forms from differential erosion of hard and soft rock.
- Meanders: river bends; oxbow lake forms when a meander is cut off.
- Deltas form at river mouths by deposition; in India, major east-flowing rivers form deltas.
Exogenic Processes: Sea Waves, Glaciers, Wind
- Sea waves erode (sea caves, arches, stacks) and deposit material.
- Glaciers (rivers of ice) carve U-shaped valleys and deposit moraines (end, lateral, medial).
- Wind in deserts shapes land by forming sand dunes, loess, and mushroom rocks (due to differential erosion).
Key Terms & Definitions
- Endogenic Forces — Earth-shaping forces from inside the planet.
- Exogenic Forces — Earth-shaping forces from outside (wind, water, etc.).
- Weathering — Breakdown of rocks into smaller pieces.
- Erosion — Movement of rock particles by agents like water or wind.
- Delta — Landform created by sediment deposition at a river mouth.
- Moraine — Glacially deposited debris.
- Richter Scale — Logarithmic scale to measure earthquake strength.
Action Items / Next Steps
- Review detailed notes or videos on each process as referenced in class.
- Prepare to differentiate between erosional and depositional features for each agent (river, wind, glacier, sea).