Movement of Lithospheric Plates

The **lithosphere** is the rigid outer layer of Earth, composed of the crust and the solid portion of the upper mantle. The term "lithosphere" is derived from the Ancient Greek words "lithos," meaning "rock," and "sphaira," meaning "sphere." The lithosphere is divided into sections of different shapes and sizes, known as tectonic plates, which are in constant motion atop the semi-fluid layer of the upper mantle called the asthenosphere The upper sections of tectonic plates are formed by two primary types of crust, which differ in age, thickness and geological composition. The continental crust is older, thicker and less dense than the oceanic crust, which is found beneath the seafloor. This model illustrates Earth's tectonic plates, which vary in size and comprise large plates, small plates and microplates. Depending on the movement of lithospheric plates relative to one another, there are three main types of plate boundary. At divergent boundaries, plates move apart from each other, resulting in the formation of new oceanic crust, typically seen at mid-ocean ridges. At convergent boundaries, plates move toward each other, leading to the destruction of crust material; depending on the type of lithospheric plate involved, this collision can create mountain ranges or oceanic trenches. Transform boundaries are characterized by plates sliding past one another along transform faults, either moving in opposite directions or in the same direction at different speeds. Transform boundaries do not lead to the formation or destruction of Earth’s crust. These tectonic boundaries represent regions where endogenous (internal) geological forces are most actively expressed. The nature of these boundaries influences the occurrence of volcanic activity, earthquakes, crustal deformation, and mountain formation. Areas with an increased flow of geothermal energy within the asthenosphere are known as hot spots. These regions are often, but not exclusively, located at plate boundaries, and they are marked on the Earth’s surface by volcanic activity and the formation of volcanic island chains (e.g., the Hawaiian archipelago). The areas of intense volcanic and earthquake activity along the western, northern and eastern edges of the Pacific lithospheric plate are referred to as the "Ring of Fire".