Module 6: The Pedosphere: Soil, Weathering, and Land Degredation

sustainable agriculture

agricultural production that meets current needs without compromising resources for future generations, while promoting environmental health, economic profit, and social and economic equity

carbon sequestration

the geoengineering strategy in which carbon is deposited in a reservoir to reduce the amount of carbon dioxide in the atmosphere

biomass

the quantity of living matter in a certain area; also, plant and animal matter and their wastes which can be used as a fuel source

pryolysis

the process of heating biomass at a low temperature (400°C - 500°C) in the absence of oxygen

biochar

a product of pyrolysis that is more durable than, and contains more than double the carbon of, ordinary biomass.

slash-and-char

an alternative form of the slash-and-burn technique in which organic matter is partially, rather than fully, burned

pedosphere

the layer of decomposed rock particles and organic matter covering Earth’s surface

critical zone

the outermost zone at Earth’s surface, where rocks, soil, water, gases, and living organisms interact in complex ways to regulate habitat and determine the availability of life-sustaining resources

physical weathering

the mechanical processes by which a rock is broken into smaller pieces (disintegration)

chemical weathering

the dissolving or altering of minerals to other forms as a result of chemical reactions that take place in rocks exposed to water and the atmosphere (decomposition)

erosion

the transport of rock and sediment deposited in sub-glacial meltwater tunnels

stress

the amount of force acting on a body per unit area

exfoliation joints

fractures in rock that are parallel or sub-parallel to Earth’s surface and divide rock into multiple thin slabs, or sheets

thermal expansion

extreme daily fluctuations in temperature cause repeated expansion and contraction of minerals and thereby the disintegration of rock

frost weathering

water expands when frozen; the volumetric expansion of water leads to high stresses within the rock; occurs when water is confined within sealed pore spaces and unable to migrate during freezing

carbonation

the chemical weathering process that occurs when carbonic acid dissolves minerals and rocks, particularly calcite and limestone

hydrolysis

a chemical weathering reaction between a silicate mineral and water, usually producing clay minerals

clay minerals

hydrous aluminum silicate minerals with a layered structure, such as kaolinite

oxidation

a process of a chemical weathering in which an element combines with oxygen to form oxide or hydroxide minerals

bioturbation

the disintegration and mixing of organic and mineral matter and aeration of soil, which often intensifies physical weathering

soil

loose material that accumulates on Earth’s surface and is composed of clay, sand, and humus

soil horizons

a unique layer of soil that differs from others because of its color, texture or composition

soil profile

a section of soil through all its soil horizons

O horizon

a litter of dead plants and animals over the surface

A horizon

form the dark, organic-rich part of soil, also known as topsoil

B horizon

mineral-rich layers that vary in color from browns, reds, and yellows to grays and blues

C horizon

consisting mainly of partially weathered parent material

rainsplash

a process of erosion of soil in which raindrops hit exposed (unvegetated) soil during intense rainstorms and lift fine particles above the soil to surface, causing some of the loosened soil to move downslope

sheetwash erosion

the removal of successive layers of rock or soil from a gentle slope by thin sheets of running water

rills

small stream channels several centimeters in width and depth that typically forms by rapid incision into sediments as a result of deforestation or the erosion of soil

gally

a small stream channel several to tens of meters deep, tens to hundreds of meters wide, and up to several kilometers long; typically formed by rapid incision into sediments associated with deforestation or erosion of the soil

land degredation

describes a suite of environmental processes associated with human activities that result in negative change to land resources over time

desertification

the transformation of land to deserts by a number of processes, including loss of vegetation, reduced soil fertility, soil erosion, and the trampling of soil by animals