18.3 Soil and Its Formation Objectives Describe the relationship between climate and soil formation. Identify different soil types and how they influence soil characteristics. All organisms that live in the soil are vital to the energy and nutrient cycles of Earth.

Soil Formation Weathering of rock forms soil –Mechanical Pounding of waves Wind Rain –Chemical Rusting of iron-containing minerals

Bedrock The igneous, metamorphic and sedimentary rock Exists as –Mountains –Cliffs –Low-lying plains Parent Rock – an area of bedrock that is the source or an area of soil.

Soil A mixture of –Mineral particles –Air –Water –Bedrock –Living and decaying organisms

Soil Profile The weathering process forms distinct soil layers –Topsoil –Subsoil –Partially weathered bedrock –Bedrock

Composition and Characteristics of Soil Major textures based on particle size –Sandy –Silt –Clay –Loam

Sandy Soils 0.05 to 2.0 mm Good drainage Good aeration Do not store water well Unsuitable for many plants

Silt to 0.05 mm

Clay Soils Smaller than mm Hold water very well Do not drain well Not much space for air Unlikely to sustain plant life

Loam Soils A mix of sand, silt, and clay Ideal for plant life Holds water Holds air

The Interaction Between Soil and Climate One of the most important factors in the formation of soil profiles Strong winds Amount of rainfall Freezing and thawing Glaciers

The End Click for Quiz

Quick Quiz QQ W_____ of rock forms soil. 2.Two types of w______: m_____ & c______. 3.B_______ exists as, mountains, cliffs, low-lying plains. 4.P_____ Rock: an area of bedrock that is the source or an area of soil. 5.S___: A mixture of, m ineral particles, air, water, bedrock, living and decaying organisms. 6.Soil Profile: t__ soil, s____, partially weathered b____, b_____. 7.Soil textures: s___, s____, c_____, l____. 8.C____: One of the most important factors in the formation of soil profiles.