Chemical weathering Flashcards
what are jennys factors of soil creation?
time, organisms, topography, climate and parent material
what is weathering?
chapin et al 2001 “weathering is change of parent rocks and minerals to produce more stable forms”, weathering involves chemical and physical processes influenced by characteristicsof parent material, environment and organism activites. lot of time for deep weathering to occur, can make assumptions about weathering from age
what is physical weathering?
fragmentation of parent material without chemical change
what is chemical change?
chemical weathering occurs when parent materials react with acidic or oxidizing substances usually in presence of water
what is regolith?
layer of broken and unconsolidated rock that covers surface of the land and bedrock everywhere
what did Dosseto state in 2012?
defined regolith as the product of bedrock weathering as this term includes aprolite and secondary minerals
what did chapin say about chemical weathering in 2012?
primary minerals dissolves releasing ions and forming secondary minerals
what happens to the saturation index?
it increases with the concentration of rection products in the water, the opposite happens to the weathering rate
what is case 1?
drying, as soil water reduces Saturation index climbs, and therefor dissolution rate falls, weathering will cease before the soil is fully dry
what is case 2?
percolating rainwater: it carries ions from the water pores reducing saturation index and increasing dissolution rate, greater water flux = greater R
what is case 3?
the effect of a soil mantle, water availability, bare rock dries instantly surface soil dries quickly, subsoil dries slowly
what is case 4?
flow path effect, in deeper soil saturation index increases and dissolution rate falls, in thicker percolation zones, dissolution rate may fall to zero
what is case 5?
vegetation/climate, High NPP means higher pCO2 in soil and more organic acids, generally high NPP means warm wet conditions so vegetation effects are hard to separate from climate effects
mineral type and weathering?
calcite and k-spar weather fastest and quartz is the slowest, calcite theoretically has a huge rate of loss, however doesn’t weather at that rate because its always close to saturation, rapidly weathering materials are always saturate rapidly.
particle size and weathering?
finer material has a much larger specific surface area, finer materials weather quicker however they saturate much faster
