Dirt and the Earth: Soil Composition & Geosphere Quiz

If soil contains organic material that has broken down over time, then that specific component is called humus. Since humus provides essential nutrients for plants, then it is the organic part of the soil composition.

If we categorize soil particles by size, then sand is the largest individual grain. If the grains are large, then they create a gritty texture when rubbed between fingers.

If we move downward through the soil layers, then we eventually reach a solid, unweathered layer of rock. If this layer supports all the soil above it, then it is defined as bedrock.

If physical or chemical forces act upon large rocks over long periods, then the rocks break into smaller sediments. If this breakdown occurs to form soil, then the process is known as weathering.

If a soil type consists of microscopic, flat particles, then there is very little space between them. If there is little space for drainage, then the soil will trap and hold the most water, which describes clay.

If the geosphere includes all the rocks, minerals, and ground found on Earth, and if soil is composed of weathered rock and minerals, then soil is a vital part of the geosphere.

If humus is formed from decaying matter on the surface, then it accumulates most heavily in the top layer. If the subsoil is located beneath the topsoil, then it contains fewer organic nutrients and more minerals.

If a soil has a balanced mix of large and small particles, then it allows for both drainage and nutrient retention. If this balance is achieved, then the resulting soil type is called loam.

If rocks are broken down by weathering, then they turn into smaller fragments. If these fragments are part of the soil, then they are referred to as sediments or inorganic matter.

If we classify soil by particle size, then the three standard categories are sand (large), silt (medium), and clay (small). If a substance is a liquid or gas like water or air, then it is a pore space filler, not a mineral particle.

If a force physically breaks a rock without changing its chemical makeup, then it is mechanical weathering. If roots grow in cracks, water freezes and expands, or water/gravity causes abrasion, then the rock breaks physically.

If organisms require oxygen and high levels of organic food (humus), then they must live in the upper layer of soil. If the uppermost mineral layer is topsoil, then that is where biological activity is highest.

If silt particles are mid-sized (between sand and clay), then they are too small to be gritty. If they are wet, then they slide past each other easily, creating a texture that feels smooth like silk or flour.

If soil particles are stacked together, then gaps remain between them. If these gaps allow for the movement of air and water to reach roots, then these spaces are called pores.

If soil formation relies on the slow weathering of rock and the gradual decay of organic matter, then the process is not rapid. If these processes occur at natural speeds, then it takes centuries to create a single inch of topsoil.

If a substance reacts with minerals to change their molecular structure, then it is chemical weathering. If acid rain touches limestone and creates a reaction that dissolves the rock, then the rock's chemistry has been altered.

If soil forms over time, then the duration of weathering matters. If the temperature (climate), the original rock type, and the layout of the land (slope) change how materials accumulate, then all these factors determine the final soil type.

If we look at the soil profile, then the layer beneath the "A horizon" (topsoil) is the "B horizon." If this layer is characterized by mineral accumulation and less organic matter, then it is the subsoil.

If a soil profile starts at the very surface, then there is often a layer of undecomposed leaves and twigs. If this layer is the most organic-rich starting point, then it is labeled as the O Horizon.

If different regions have different parent rocks and different climates, then the weathering products will vary. If the materials vary, then the percentage of sand, silt, and clay in the soil will differ from one location to another.