Geomorphic Processes
"The face of the Earth is a canvas. The artist is never done."
1. Chapter Overview
The Earth's surface is CONSTANTLY CHANGING. This chapter explains the TWO CATEGORIES of forces that shape it: ENDOGENIC (internal — diastrophism and volcanism) which BUILD up the land, and EXOGENIC (external — weathering, mass wasting, erosion, deposition) which WEAR it down. Together, they're the GEOMORPHIC PROCESSES that create and destroy landforms.
2. Endogenic Processes (Internal — BUILD the Land)
Diastrophism (Tectonic Movements)
- Orogenic: MOUNTAIN-BUILDING (horizontal forces → folding, faulting)
- Epeirogenic: CONTINENT-BUILDING (vertical forces → uplift and subsidence of large areas)
- Earthquakes: sudden release of accumulated stress along faults
Volcanism
- Movement of MAGMA from the interior to the surface
- Creates: volcanoes, lava plateaus, volcanic mountains
- Intrusive (magma cools BELOW surface → batholiths, dykes, sills) and Extrusive (lava erupts ON SURFACE)
3. Exogenic Processes (External — WEAR Down the Land)
Exogenic processes derive their energy from the SUN (climate) and GRAVITY. They are:
A. Weathering (In-Situ Breakdown)
| Type | Process | Key Points |
|---|---|---|
| Physical (Mechanical) | Rock broken into smaller pieces WITHOUT chemical change | Frost action (freeze-thaw), thermal expansion, pressure release (unloading) |
| Chemical | Rock DECOMPOSED — chemical composition CHANGES | Solution (limestone dissolves), oxidation (rust), hydration, carbonation |
| Biological | Living organisms break rocks | Plant roots, burrowing animals, lichens (chemical + physical) |
B. Mass Wasting (Movement Downslope)
- Movement of rock and soil DOWNHILL under GRAVITY
- FAST: landslides, rockfalls, debris flows
- SLOW: soil creep (millimeters per year — fences, walls tilt over time)
- Triggered by: heavy rain, earthquakes, slope undercutting
C. Erosion and Deposition
- EROSION: removal of material by MOBILE AGENTS (running water, wind, glaciers, sea waves)
- TRANSPORTATION: carrying material away
- DEPOSITION: dropping material when the agent loses energy
| Agent | Erosional Landforms | Depositional Landforms |
|---|---|---|
| Running Water | V-shaped valleys, gorges, waterfalls | Floodplains, deltas, alluvial fans |
| Wind | Mushroom rocks, deflation hollows | Sand dunes, loess deposits |
| Glaciers | U-shaped valleys, cirques, fjords | Moraines, drumlins, eskers |
| Sea Waves | Cliffs, sea arches, stacks | Beaches, sand bars, spits |
4. The Relationship — Endogenic vs Exogenic
- Endogenic forces CREATE relief (mountains, plateaus, continents)
- Exogenic forces REDUCE relief (wearing down, filling in)
- They work SIMULTANEOUSLY and IN OPPOSITION
- The landscape we see is the RESULT of this ongoing contest
5. Soil Formation (Pedogenesis)
- Soil = weathered rock material + organic matter (humus) + water + air
- Factors: parent material, climate, topography, organisms, TIME
- Soil is the INTERFACE where the lithosphere, atmosphere, hydrosphere, and biosphere MEET
6. Exam Focus
- Endogenic vs Exogenic — definitions and examples
- Weathering types (physical, chemical, biological)
- Mass wasting — what it is, fast vs slow
- Agents of erosion and their landforms
- Soil formation factors
7. Common Mistakes
- Weathering and Erosion are the same — Weathering = breakdown IN PLACE (in-situ). Erosion = removal AND transport by mobile agents. Weathering PREPARES material; erosion MOVES it.
- Physical and chemical weathering happen separately — They OFTEN WORK TOGETHER. Physical weathering increases surface area → chemical weathering attacks more surface. They REINFORCE each other.
8. Conclusion
The Earth's surface is a BATTLEGROUND between forces that BUILD (endogenic) and forces that WEAR DOWN (exogenic). The landscapes you see — mountains, valleys, plains, coastlines — are the temporary truce in this endless war.
The Grand Canyon is the Colorado River's autobiography. Every landform is a process, frozen in time.
