An acid is a substance having a pH of less than 7 when dissolved in water. Ecologists apply the term acidic to plant communities growing in rather acidic and nutrient-poor soils. Acidic soils result f [..]

Related to alluvium or floodplains.

Sediment deposited by flowing streams or rivers in floodplains and streambeds/riverbeds. Different sizes of sediment particles are deposited, depending on the water velocity related to the location wi [..]

A former floodplain terrace, or alluvial landform that is no longer subject to flood events, but is instead in the uplands. At Rock Creek Park, some of the highest hills are topped with coarse sand an [..]

See slope aspect.

A base is a substance having a pH above 7 when dissolved in water. A basic substance is capable of neutralizing acids. Base elements, such as calcium, magnesium, and sodium, are one class of such subs [..]

See base, basic, and element.

A rock mineral containing base elements.

Solid rock that underlies unconsolidated material such as soil and fragmented rock, or is occasionally exposed as rock outcrops.

A rock-forming mineral high in iron, magnesium, and potassium, dark brown or black in color. A common kind of ‘mica’ (a group of soft minerals that tend to occur in flakes or sheets. Quoted from Stewa [..]