I belive it it O because <span>An O horizon has at least 20% </span>organic matter<span> by mass. Two main scenarios result in the formation of an O horizon: saturated, </span>anaerobic<span> conditions (wetlands) or high production of leaf litter in forested areas. Anaerobic conditions slow the </span>decomposition<span> process and allow organic material to accumulate. An O horizon can have various stages of decomposed organic matter: highly decomposed, sapric; moderately decomposed, hemic; and minimally decomposed, fibric. In a fibric O layer, plant matter is recognizable (e.g., it is possible to identify a leaf). Sapric material is broken down into much finer matter and is unrecognizable as a plant part. Hemic is in between sapric and fibric, with some barely recognizable plant material present. It is possible to have multiple O horizons stacked upon one another exhibiting different decomposition stages. Because of their organic content, these horizons are typically black or dark brown in color. The dominant processes of the O horizon are </span>additions<span> of organic matter, and </span><span>transformations </span><span>from fibric to sapric
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Answer:
<u>geologic unit</u>
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When reading a geologic map, rock units are labeled with letter codes. The first upper-case letter indicates <u>age of the geologic unit</u>, while the following lower case letters represent <u>geologic unit's name or the type of rock of which it is comprised.</u>
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Explanation:
Geologist have divided the history of the earth into 4 main periods of time; the Eons, the Eras the Periods and the Epoch. On a geological map, an initial capital letter is usually followed by one or more lower case letters while the lower case letters indicate either the name of the unit, if it has one, or the type of rock, if the unit has no name.
The first one is a the second one is a i think the third one is a and the last one is b
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