Andisols & Histosols

Joe & Mike

Andisols: General Chracteristics

• Dominated by short-range-order minerals. • Include weakly weathered soils with much

volcanic glass as well as more strongly weathered soils.

• Volcanic glass is one of the characteristics used in defining Andic soil properties.

Andisols WorldMostly in Pacific Ring of Fire, Iceland, basically near volcanos

Andisols: USA

Andisols: Minnesota

• N/A

Andisols: Diagnostic Horizons

• May have any diagnostic epipedon, provided that the minimum requirements for the order are met in and/or below the epipedon.

Andisols: Typical EnvironmentsClimate: form in all soil moisture and all soil temperature regimes, except pergelic (perma frost). • Formation of Andisols in arid regions is limited because of slow weathering of volcanic parent materials.

Vegetation: Andisols develop under a variety of vegetation types ranging from coniferous and deciduous forest, tundra, to shrubs.

Relief: Andisols are found on any topography, most often they occur on steep slopes formed by volcanic activity. They can occupy any position on the landscape and can occur at any elevation .

Parent Material: Most Andisols formed from volcanic ejecta such as ash, pumice, cinders, and lava. • Volcanic terrains have a greater variety of rock-types than other surface environment on earth.

These terrains include lavas, pyroclastic deposits (from explosions), and deposits from a wide range of sedimentary processes that occur in volcanic terrains.

• The nature of volcanic material ejected from a volcano varies greatly in time and space and determines the size of particles, composition of materials, and depth of volcanic material deposited. Rapid cooling of the molten materials upon ejection prevents crystallization of minerals with long range atomic order, and the resulting product is vitric material or volcanic glass, which are dominated by amorphous, short-range-order minerals.

Time: Because volcanoclastic material is more weatherable than crystalline materials Andisols do not need very long time periods to form

Andisols: Some Pictures

Andisols: % Ice free land surface coverage

• Andisols: ≤ 1%