i8 PRINCIPLES OF STRATIGRAPHY 



2. Corrasion, a filing process. 



a. by wind = eolian corrasion. 



b. by running water= river corrasion. 



c. by ice = glacial corrasion. 



d. by waves ^ abrasion. 



e. by organisms = gnawing, etc. 



3. Quarrying (closely related to physical clastation). 



a. by wind (rare) undermining (decapitation of 



erosion monuments), etc. 



b. by running water = undermining (recession 



of Niagara). 



c. by ice=:plucking, sapping. 



d. by waves = tunneling and undermining. 



e. by organisms, plant-wedging, plucking, etc., 



man's work. 

 B. Chemical. 



4. Corrosion. 



a. by air — or evaporation (snow, ice). 



b. by water (aqueous corrosion) — or solution. 



c. by heat — igneous corrosion or melting. 



d. by organisms. 



TRANSPORTATION. 



I. Mechanical. 



A. In suspension (in, and moving with the mass). 



1. Atmospheric — by wind: eolian transport. 



2. Hydrosphcric. 



a. by waves, ocean and lake currents, tidal cur- 



rent, undertow, etc. 



b. by rivers (fluviatile transport). 



c. by ice, englacial till ; ground moraine, etc. 



d. carried by floating host — such as : 



(i) floating dead organisms (stones held by 

 floating trees, etc.). 



(2) icebergs, shore ice, etc. 



(3) rafts, ships, etc. 



3. Pyrosphcric — suspended in molten lava. 



4. Biospheric — transported by animals either ex- 



ternally or internally. 



B. Basally, by shoving, rolling, sliding, etc. 



I. Atmospheric — rolling by wind, as sand of sand 

 dune, etc. 



