our planet

The earth has a solid inner core that is surrounded by a liquid outer core. Surrounding the entire dense, metallic core is a thick, hot, convective layer called the mantle. The crust consists of many continental and oceanic plates that have slowly moved and changed positions on the globe throughout geologic time. The movement of these large plates (plate tectonics) has caused the earth’s exposed land surface to change position and shape. Tremendous forces, such as convection, tension and compression, have caused the upper crustal layers to fold and fault. Earthquakes and volcano activity have resulted along the borders of the plates. These forces, along with weathering and erosion, have caused large quantities of material to be deposited in varying amounts across the globe.

            Physical and chemical processes have constantly acted on earth material to form, change and reform three general types of rocks. These processes form minerals, which are substances that consist of certain elements to form compounds that appear to be uniform throughout. Other minerals are pure substances and are made of a single element. Each mineral has unique physical and chemical properties that allow it to be of economic value to humans. Minerals can combine to form rocks. Heat, pressure, erosion, and chemical processes can change rock from one type to another. Earth material can eventually be in the form of any of the rock types found throughout geologic history. This process is known as the rock cycle. 

            The upper-most layer of the continental crust is covered by soil. The ingredients in soils can vary from neighborhood to neighborhood and around the earth. Different soils have different properties and compositions of sand, silt, clay and humus. Soils have many properties such as texture, particle size, pH, fertility and ability to hold moisture. Depending upon the combination of properties, soils have a great variability in their ability to support structures and plant growth. Humans have continually decreased the amount of soil that is available through poor land-use methods, soil nutrients depletion, and the construction of structures that cover the soil (such as highways, parking lots and buildings). Structures that cover the soil also affect a run-off pattern, which leads to another set of problems.

            Technology such a remote sensing has allowed humans to better study the human impact on soil quality and erosional processes so that soil can be protected and preserved. Over time, remote sensing information can tell us how humans are constantly changing the surface of the earth. Technologies can also assist in finding ways to help prevent erosion. It is important that humans be stewards of the pedosphere.