Geology is a branch of Earth science that studies the structure of the solid Earth, the rocks that make up it, and the processes that occur on it over time. Stratigraphy can also refer to the study of the solid Earth features of any terrestrial planet (such as Mars or the Moon). Stratigraphy describes the structure of the subsurface, and the processes that shaped that structure. Stratigraphy also provides the tools needed to determine the relative and absolute ages of the rocks at a particular site, as well as to describe the history of those rocks. By combining these tools, stratigraphers can chronicle the geological history of each land and determine its age. And stratigraphy provides the essential evidence for plate tectonics, the evolutionary history of the Earth, and the Earth's past climates.