page_title: Geology
section_title: Rock
hierarchical_section_title: Geology / Geologic materials / Rock
caption_attribution_description: Deutsch: Gediegen Gold Fundort: Mina Zapata, Santa Elena de Uairen, Simón Bolívar, Venezuela Größe: 3.46 x 3.12 x 1.79 cm. English: Native gold Locality: Mina Zapata, Santa Elena de Uairen, Bolívar, Venezuela Size: 3.46 x 3.12 x 1.79 cm. Français&#160;: Or natif Localité&#160;: Mine Zapata, Santa Elena de Uairén, État de Bolívar, Venezuela Taille 3.46 x 3.12 x 1.79 cm
context_page_description: Geology is an earth science concerned with the solid Earth, the rocks of which it is composed, and the processes by which they change over time. Geology can also include the study of the solid features of any terrestrial planet or natural satellite such as Mars or the Moon. Modern geology significantly overlaps all other earth sciences, including hydrology and the atmospheric sciences, and so is treated as one major aspect of integrated earth system science and planetary science.
  Geology describes the structure of the Earth on and beneath its surface, and the processes that have shaped that structure. It also provides tools to determine the relative and absolute ages of rocks found in a given location, and also to describe the histories of those rocks. By combining these tools, geologists are able to chronicle the geological history of the Earth as a whole, and also to demonstrate the age of the Earth. Geology provides the primary evidence for plate tectonics, the evolutionary history of life, and the Earth's past climates.
context_section_description: The majority of research in geology is associated with the study of rock, as rock provides the primary record of the majority of the geologic history of the Earth. There are three major types of rock: igneous, sedimentary, and metamorphic. The rock cycle 
  illustrates the relationships among them (see diagram).
  When a rock solidifies or crystallizes from melt (magma or lava), it is an igneous rock. This rock can be weathered and eroded, then redeposited and lithified into a sedimentary rock. It can then be turned into a metamorphic rock by heat and pressure that change its mineral content, resulting in a characteristic fabric. All three types may melt again, and when this happens, new magma is formed, from which an igneous rock may once more solidify.
caption: Native gold from Venezuela
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