Weathering Processes and Soils

These flashcards cover key concepts related to weathering processes and soil formation, including definitions and characteristics of various types of weathering, soil profiles, and the importance of soil in the ecosystem.

What is weathering?

The processes by which rocks are chemically altered or physically broken down into fragments at or near the earth’s surface.

What are the two main types of weathering?

Physical (Mechanical) weathering and Chemical weathering.

What is Physical Weathering?

The process that breaks down rocks into progressively smaller grains without changing the mineral composition.

What is the Wentworth Scale used for?

To classify sediment and detritus by size from largest to smallest.

What are the classifications of sediment according to size?

Boulders, Cobble, Pebbles, Sand, Silt, Clay.

What causes joints and fractures in rocks?

They form due to release of confining pressure and tectonic stresses.

What are the common types of Mechanical Weathering?

Frost wedging, Salt wedging, and Root wedging.

What is dissolution in terms of chemical weathering?

The process where natural waters, which are slightly acidic, break down rock material.

What role does hydrolysis play in chemical weathering?

It breaks down minerals by the addition of water, particularly affecting silicate minerals.

What is oxidation in geological terms?

A chemical reaction during which an element loses electrons, often seen in rusting.

How does weathering contribute to soil formation?

Weathering forms the basis for soil by breaking down rocks into sediments that can support plant life.

What are the main factors affecting soil formation?

Parent material, climate, topography, time, and biological interactions.

What is the O-horizon in a soil profile?

The organic layer composed mostly of humus.

How many USDA soil orders are there, and which three should we know?

There are 12 soil orders; we should know Alfisols, Aridisols, and Oxisols.

What are Alfisols?

Soils that form in semi-arid to humid areas, typically under hardwood forests, having high fertility.

What are the characteristics of Aridisols?

Soils that form in arid or semi-arid climates, with no O-horizon and characterized by calcium carbonate accumulation.

What defines Oxisols?

Highly weathered soils that undergo extreme leaching, low fertility, and develop in hot, humid climates.

Why is soil erosion a concern?

It leads to loss of arable soil, costing significant damage annually and threatening food production.