Denudation
Origin of Landscapes (18th century)
- Observations of changes to landscape
- Erosion or decrease of land
- Valley erosion
- Shoreline retreat due to waves
- Cavern collapse
- Sea level rise (Baltic)
- Caldera collapse
- Deposition or increase of land
- Flood deposits alongside rivers
- Coastal marshes (fens)
- Tallus debris
- Deltas
- Lava flows, ash beds
- General movement of material from elevated areas to lower elevations
- Erosion or decrease of land
- Models to explain landscapes
- Original landscape
- Landforms present since the start
- Little modification since then – established early
- Works for precipitation of uneven Primary rocks
- Result of the Deluge
- Surface remodeled by the Flood
- Flood dissolved and eroded the old world
- Some material precipitated
- Eroded debris made into hills
- Topography not original but result of Flood
- Formed by earthquakes and volcanoes
- Collapse of subterranean caverns (an 17th century idea)
- Volcanic deposits elevate surface
- Ongoing alteration
- Original landscape
Denudation Dilemma
- Basic Question:
- How maintain land in the face of evidence of ongoing persistent erosion over long time periods?
- Problematic due to Deist orientation of Enlightenment
- God made world, then left it alone
- Designed to be the abode of humans
- How to reconcile it with natural history
- Denudation renovates the landscape
- Doesn’t really alter the landscape
- Renovating force counteracts erosion by causing rocks to grow
- Elements of “petrified seed”
- Least popular solution
- Denudation is beneficial
- Erosion rejuvenates the land (ex.: soils)
- Lowered mountains are advantageous
- Limited impact so not real threat
- Denial of the significance of denudation
- Slopes are stable – no net change
- Limited time, so impact limited: De Luc’s natural chronometers
- Roman ruins buried by sediment
- Minor infill in lakes
- Alpine talus sheets still growing but mountains still tall
- Natural system repairs itself
- Denudation renovates the landscape