Final answer:
Clay is a sticky fine-grained substance that becomes mouldable when wet and is used to make bricks, pottery, and ceramics. It has been formed over millions of years and is a crucial part of the soil that supports plant life and human developments. It's also part of the material class known as terracotta, meaning 'baked earth'.
Step-by-step explanation:
The term you are looking for is clay. Clay is a stiff, sticky fine-grained earth that can be yellow, red, or bluish-gray in color. It frequently forms an impermeable layer within the soil and has a significant role in various human activities. When clay is mixed with water, it becomes mouldable and can be shaped to create items such as bricks, pottery, and ceramics. Through geological processes over millions of years, including weathering and erosion, clay has become a key component of the soil. It derives its plasticity from fine particles of silt, which contain minerals like feldspar and silica, and alkalis such as iron, which contribute to its characteristic colours.
The ability to Mold clay when wet and its hardening upon drying and baking are essential properties for the production of building materials and art forms. Ancient civilizations had easy access to clay because rivers would cut through topsoil, exposing its layers. Furthermore, clay can also be a component of sedimentary rocks, with a grain size so fine that individual minerals cannot be observed without microscopic assistance. Soil, in a broader context, is considered any unconsolidated material above bedrock, which clay is a part of. Hence, clay plays a crucial role not just in the environment but also in human history and development.
Caliche is another related material that forms in soil within semiarid to arid environments. On the other hand, terracotta, which literally means 'baked earth', directly references the use of clay-based earthenware for making durable sculpted items and construction materials.