Soils & Groundwater VA SOL ES. 8 (a,c,d,e,f)
What is SOIL? Soil is dirt (bits of weathered rock) mixed with organic material. Organic material is anything that is alive or has ever been alive Decaying organic material is called humus
Soil Development Soil develops over time into different layers called horizons. Rocks get weathered Animals, fungi, bacteria, etc. lives in the parent rock, then dies and decays – (humus). Humus mixes in with the weathered rock forming soil Water percolates down carrying minerals through the forming layers.
ABC’s of Soil Horizons O = organic. Humus is found here. Leaves, twigs, etc. A = topsoil. Mix of weathered rock and humus B = subsoil. Mix of weathered rock with very little organic matter C = weathered parent rock – rock that is barely broken down Bedrock = un-weathered parent rock.
Soil Profiles
Maturity vs. Fertility When all soil horizons are present, you have a mature soil profile Minerals in the soil determines the soil’s fertility
Factors Affecting Soil Development Climate: mostly related to rainfall Polar Soils: permanently frozen (permafrost) Temperate Soils: diverse, more mature profile. Most fertile. Desert Soils: lots of salts, little organic matter Tropical Soils: very weathered, too much organic activity, infertile soil
Factors Affecting Soil Development Topography: Affects the thickness of soils Soils on slopes are thin Soils in valleys are thick and fertile
Factors Affecting Soil Development Time: The longer the parent rock has been around, the more weathered it can become and that means more developed soil profiles.
Water on Earth Occurs as solids, liquids, and gases. Continuously being passed through the HYDROLOGIC cycle (water cycle)
Earth’s Freshwater Our supply is finite meaning that it WILL run out. Only 3% of the Earth’s total water supply is fresh water, the rest is salt water Most of this freshwater is either locked in glaciers, ice caps, or permafrost.
Where do we find freshwater we can use? Standing water (lakes and ponds) Flowing water (rivers and streams) Groundwater – totals to 0.6% of the Earth’s freshwater source
Precipitation that does not run off the Earth’s surface into lakes or streams or evaporate into the atmosphere is absorbed into the Earth’s permeable soil and solid rock as ground water
Groundwater Can only be “pulled” into the ground if the material in the ground allows water to flow through it. Permeability : measures of the ability of a rock to transmit water or other liquids through it. Porosity: the amount of air space in a substance
Lower Permeability Higher Permeability Higher Permeability Lower Permeability
Aquifers and Zones Water exists underground in zones including the: Water Table – boundary between the two zones, groundwater located below the water table Zone of Saturation (saturated with water) – area in the ground where water saturates all of the pore space Zone of Aeration (full of air) – area where water percolates down to the ground water Aquifers are rock formations that hold water
Zone of Aeration
Importance of Freshwater Plants need ground water for growth Groundwater is an important source for homes, industry, and agriculture. We kinda NEED water to not die…
Threats to Freshwater Resources Overuse – we simply run out! Subsidence – land sinking below our feet Pollution - sewage from faulty septic systems and cows, industrial waste, landfills, and agricultural chemicals like fertilizer. Pollution spreads quickly in groundwater! Chemicals - arsenic and other small ions that can not be absorbed through the natural filter of fine-grained sediments. Salt - in areas where salt water is under fresh water, the water is too salty to drink
Watersheds All land area that “drains” into a stream system is called a watershed There are 21 primary watersheds in the US
Virginia Watershed 3 major regional watershed systems in VA We live to the East of the Eastern Divide so our water flow to the Chesapeake Bay Water that lands else where will either lead to the North Carolina Sounds or the Gulf of Mexico