Topographic Features
From Open Energy Information
Topographic Features:
Topography is the shape and arrangement of physical features on a surface. In the case of geothermal exploration, horst and graben topography or volcanoes may indicate underlying structures and their associated processes that may be conducive to the development of geothermal systems. Although topographic features are very preliminary indicators of geothermal systems, they are easily identifiable.
| Topographic Features | Description |
| Mountainous | Mountainous regions are characterized by rugged terrain and steep topography formed through complex structural deformation. Mountainous regions typically occur adjacent to convergent plate boundaries (e.g. subduction zones or at the collision zone between two or more continental tectonic plates) or their fossil equivalents. Mountains may also be present along the margins of major rift zones, where extension has resulted in crustal thinning and the formation of down-dropped basinal blocks bounded by normal range front faults. |
| Horst and Graben | A "horst and graben" is a crustal-extension structure, composed of a series of normal faults, typical of the Basin & Range region of the US and Turkey’s West Anatolian Extensional Province. From the surface they appear as a series of ridges (horsts) and valleys (grabens) that run perpendicular to the direction of extension. |
| Shield Volcano | Shield volcanoes produce far flowing lava making the volcano's profile low and wide. |
| Flat | Flat terrains are characterized by the absence of major topographic features. Flat topography is typically encountered in areas that have experienced minimal past or present tectonic activity, but may also be present as relatively flat valley floors in caldera depressions and rift zones. |
| Lava Dome | Lava domes, also known as volcanic domes, are bulbous mounds formed via the slow eruption of viscous lava from a volcano. They are commonly encountered in the craters or on the flanks of large stratovolcanoes. |
| Stratovolcano | Stratovolcanoes, also known as composite volcanoes, are conical volcanoes composed of multiple layers of intermediate to felsic lava, ash, and other volcanic debris. Their steep profiles are the result of the high viscosity of less mafic lavas, which prevents them from flowing great distances during eruption and cooling. |
| Cinder Cone | Cinder cones, also known as scoria or spatter cones, are a relatively simple type of volcano consisting of a steep conical pile of volcanic ash and tephra. They exhibit a lower profile than stratovolcanoes (usually rising no more than a thousand feet above the surrounding topography), and typically have a bowl-shaped depression at their summits. They form primarily from the eruption of pyroclastic ejecta and are commonly encountered on the flanks of stratovolcanoes, shield volcanoes, and calderas. |
| Caldera Depression | Calderas form from the catastrophic eruption of large amounts of felsic lava and ash. Emptying of the magma chamber and subsequent collapse of the overlying volcanic edifice forms a ring-shaped caldera depression up to several kilometers in diameter. The edges of the underlying magma chamber are roughly marked by a ring fracture zone that acts as a conduit for ongoing volcanism and hydrothermal activity. |
| Resurgent Dome Complex | Resurgent domes are encountered near the center of many caldera depressions, and form via uplift of the caldera valley floor due to movement in the underlying magma chamber. Resurgent domes do not form via eruption of lava, but from the migration of magma in the subsurface that results in deformation of the overlying crust. Resurgent domes typically host numerous deformation structures that act as conduits for hydrothermal fluids in the shallow crust. |
These values are part of Category:Topographic Features, and are used for the Property:TopoFeatures.