=Dominant processes.=—Three sets of processes, now in operation on the surface of the lithosphere, have given rise to most of the details of its configuration, and even many of its larger features. These processes have been designated _diastrophism_, _vulcanism_, and _gradation_. _Diastrophism_ includes all crustal movements, whether slow or rapid, gentle or violent, slight or extensive. Many parts of the land, especially along coasts, are known to be slowly sinking relative to the sea-level, while other parts are known to be rising. The fact that rocks originally formed beneath the sea now exist at great elevations, and the further fact that areas which were once land are now beneath the sea, are sufficient evidence that similar changes have taken place in the past. _Vulcanism_ includes all processes connected with the extrusion of lava and other volcanic products, and with the rise of lava from lower to higher levels, even if not extruded. Vulcanism and diastrophism may be closely associated, for local movements at least are often associated with volcanic eruptions, and more considerable movements may be connected with the movements of subsurface lavas, even when the connection is not demonstrable. _Gradation_ includes all those processes which tend to bring the surface of the lithosphere to a common level. Gradational processes belong to two categories—those which level down, _degradation_, and those which level up, _aggradation_. The transportation of material from the land, whether by rain, rivers, glaciers, waves, or winds, is _degradation_ and the deposition of material, whether on the land or in the sea, is _aggradation_. Degradation affects primarily the protuberances of the lithosphere, while aggradation affects primarily its depressions. +Astronomic Geology.+