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Hydromorphic soils are soils associated with marshes, swamps, bogs, or poorly drained flat uplands. All are considered intrazonal soils because of poor drainage.

Bog soils are forced under bog vegetation in regions of cool, moist continental climates. Continental glaciation in North America and Europe left countless basins that have since been largely filled by a succession of water-loving plants. Here the soil is saturated most of the time and plant decay is greatly retarded. The partly decomposed plants of the bog therefore accumulate into an upper peat layer 3 to 4 ft thick. Below this is a horizon of sticky, structureless clay, known to soil scientists as the glei (also gley) horizon. It is of gray-blue colour and is largely impervious to water seepage.

Meadow soils (Wiesenboden) are formed on the flood plains of streams where drainage is somewhat better than in the bogs, but is nevertheless poor. These areas are extensively used in the humid middle-latitude climates as pastures be-cause the grass grows rapidly and densely. A thick, humus-rich layer is developed, overlying a sticky gley horizon. A similar process of soil development takes place on poorly drained sites at the bases of hill slopes where there is a tendency for water to collect.

The name humic-glei soils have been proposed for the meadow soils in combination with half-bog soils.

At high altitudes, where the alpine tundra climate prevails, alpine meadow soils are found. Dark in colour these soils support a growth of grasses, sedges, and flowering plants.

Strongly leached soils developed on flat or gently sloping, elevated surfaces are known as planosols. The soil horizons are abnormally thick because of slow removal by erosion. Planosols have a thick, dense clay horizon in humid climates. In sub humid climates planosols have a dense, cemented horizon.

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