Introductory Concepts and Earth Science - AP Environmental Science

There is a sizable bank of nitrogen in the atmosphere that can be fixed by certain bacteria (and plants that harbor this bacteria in their roots), while phosphorus originates largely from bedrock and is released into the soil in limited quantities. Nitrogen can be fixed from a collective atmosphere that is three-quarters nitrogen, while phosphorus is more region-specific and can be harder to replace than nitrogen once it's depleted. Farms located in phosphorus-poor regions often have to rely on mined phosphates.

Phosphorus defficiency is a challenge to resolve because phosphorus stores are almost exclusively in bedrock and sediment, and there is only as much as the bedrock weathers over time. Manure is very rich in phosphorus, and since plants do not fix phosphorus directly into the soil, applying manure and then covering with mulch is the best option.

Sheet erosion occurs when either wind or widespread shallow water with a slow current degrades the soil in thin layers. A flooded and uneven field that is mostly bare soil will likely experience sheet erosion because the erosion is shallow and uniform.

The correct response is intensification. The term intensification refers to farmers working the fields more heavily and intensely. All the other responses are techniques used by farmers to conserve soil.

The correct response is waterlogging. In waterlogging, water covers plant roots and soils with water - preventing soils from absorbing oxygen from the air. If the water covers the soil surface for too long, plants begin to die because their roots can't absorb oxygen and/or carbon dioxide from the atmosphere in order to undergo respiration. Salinization involves the increase in salt content of soil. Sheet erosion is the process by which thin layers of soil are moved due to the force of rain drops and overland flow. Gully erosion involves the formation of gullies (small valleys) due to intensive erosion by water. Rill erosion involves water creating rills, small channels through which water flows.

All of these components make up soil. Differences in ratios of these components account for different soil types.

Soil categories are referred to as "horizons." Additionally, a vertical cross section of soil horizons is called a "profile."

Clay has the smallest particles, followed by silt, which contains larger particles than clay, but smaller particles than sand. Loam is a mixture of these three types of soil.

The correct response is soil. Soil is a mix of sand, clay, pebbles, and silt. It is the foundation of all our ecosystems.

The correct response is cohesion. This property measures how well a soil clumps together or breaks apart.

The correct response is permeability. This measure how quickly water can move through any substance - including soil.

Leaching occurs when percolating water transports materials from the top soil layers. Usually, these materials are illuviated(deposited) to a lower level.

The O Horizon is composed of humus (organic matter), the A Horizon is a mixture of minerals and organic matter, the B Horizon is composed mainly of minerals and the D horizon is solid bedrock. The C Horizon best fits this definition, as it is the layer above the bedrock, consisting mostly of weathered rock fragments.

The correct response is O Horizon. This O horizon is the layer closest to the surface - typically between the depths of 0 to 2 inches, and contains freshly fallen leaves, plant litter, and lots of other organic matter.

The correct response is B Horizon. The B horizon is referred to as the zone of accumulation because all the clay, minerals, and subsoil that is washed into it via illuviation from the overlying layers of soil. The B horizon is usually dark red or brownish due to the presence of clay and iron oxides.

Metamorphic rock is the only kind of rock that is formed below the Earth's crust. Igneous rock is formed by lava and volcanic activity. Sedimentary rock is formed by the collection of sand and other microscopic components that are fused together. Generally, the last two kinds of rock are found in the crust only, unless they are melted into lava.

There are six types of soil horizons and each has different chemical or physical properties. Each type of soil has a different number of horizons. The horizons start at the parent material (bedrock) and continue up to the surface.

The correct response is humus. This is one of the most important components to soil communities. Humus is formed as things like leaves, branches, and other vegetation breakdown (slowly) over time. Earthworms and microbes help speed up the process of breaking down dead organic matter into humus.

Desalinization involves heating seawater to a boil, resulting in pure, distilled water vapor with no impurities. While any ferally-funded project is subject to environmental assesments, the major roadblock for these facilities is the heat energy required to distill the seawater.

When atmospheric carbon dioxide reacts with ocean water, they combine to product the bicarbonate iron, or . This ion acts as a buffer in the sea water, allowing the pH to remain relatively stable. While neither methane, glucose, nor carbon monoxide occur in large enough quantities in salt water, phosphoric acid actually contains no carbon.