Gradational Processes

often primary factor influencing landforms "erosional remants" (mass gone) gradation can reach base level (sea-level) uplift counteracts gradation forces tectonic uplift or isostatic rebound water - most important element gravity provides chief energy source denudation - lowering of the continent weathering, mass wasting, erosion

• breaking large pieces into smaller ones
  • that are ultimately carried away by water, wind, and gravity
  • also exposed more surface area to allow chemical weathering
    
    
• joints, fractures, and faults are primary weak zones
  • freezing water in joints is primary as it expands (about 9%)
  • talus slopes are indications of this "frost wedging" process
    
    
• salt wedging in porous sandstone
  • capillary action creeps into vertical cracks
  • after evaporation creates growing crystals
  • S.W. deserts and Anasazi Ruins
    
    
• exfoliation - rock layers (like onion layers) that unload pressure
  • dome shaped landforms
  • found throughout granite regions (Sierra Nevada Mtns)

• forms new, weaker (soft) minerals easily washed away
• absorbs water in chemical reaction making rock’s volume larger
• dissolve minerals with weak acidic properties
  • can only take place in presence of water (oxygen catalyst)
  • higher temperatures rapidly increase reaction too (like tropical areas)
    
    
• oxidation - chemical union of oxygen (H2O) with other substances
  • like rust (iron and oxygen)
  • metalic oxides easily dissolve and wash away
    
    
• hydration and hydrolysis - attaching water molecules to other substances
  • hydration chemically removes water from substance
  • hydrolysis - chemically adds water to substances, compound or minerals to weaken them
    • e.g. disintegrating granite
      
      
• Carbonation - carbonic acid (CO2 + H2O)
  • limestone is classic rock that easily melts away with water and mild acid
  • pollutants have increased erosion by making rain more acidic
  • destroys ancient ruins like Greek Parthenon and Taj Mahal in India
  • other plants (like oak leaves) produce acidic soils and solutions

• spectacular landscapes
  • resistant rock like volcanic, limestone in arid regions, metamorphic
    • Monument Valley, Grand Canyon, Bryce in Utah
      • towering mesa, steep cliffs, strange pinnacles