Natural England - Geology glossary (U to Z)
Geology glossary (U to Z)
This page of the glossary covers U to Z. You can navigate to the next section from the links at the bottom of this page.
| Unconformity A boundary separating two or more rocks of markedly different ages, marking a gap in the geological record. |
| Variscan Orogeny The mountain-building period of central Europe during the Carboniferous and Permian Periods. (also referred to as the Hercynian Orogeny) |
| Volcanicarc A chain of volcanoes fuelled by magma that rises from an underlying subducting ocean plate. |
| Volcano The solid structure created when lava, gases, and hot particles escape to the Earth's surface through vents. Volcanoes are usually conical. A volcano is "active" when it is erupting or has erupted recently. Volcanoes that have not erupted recently but are considered likely to erupt in the future are said to be "dormant." A volcano that has not erupted for a long time and is not expected to erupt in the future is "extinct." |
| Weathering The process by which exposure to atmospheric agents, such as air or moisture, causes rocks and minerals to break down. This process takes place at or near the Earth's surface. Weathering entails little or no movement of the material that it loosens from the rocks and minerals. |
