Landforms are categorized by characteristic physical attributes such as their creating process, shape, elevation, slope, orientation, rock exposure, and soil type.
In geology and related fields, a stratum is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as either bedding surfaces or bedding planes. Prior to the publication of the International Stratigraphic Guide, older publications have defined a stratum as either being either equivalent to a single bed or composed of a number of beds; as a layer greater than 1 cm in thickness and constituting a part of a bed; or a general term that includes both bed and lamina. Related terms are substrate and substratum (pl.substrata), a stratum underlying another stratum.
In geology, a dike or dyke is a sheet of rock that is formed in a fracture of a pre-existing rock body. Dikes can be either magmatic or sedimentary in origin. Magmatic dikes form when magma flows into a crack then solidifies as a sheet intrusion, either cutting across layers of rock or through a contiguous mass of rock. Clastic dikes are formed when sediment fills a pre-existing crack.
A flood basalt is the result of a giant volcanic eruption or series of eruptions that covers large stretches of land or the ocean floor with basalt lava. Many flood basalts have been attributed to the onset of a hotspot reaching the surface of the earth via a mantle plume. Flood basalt provinces such as the Deccan Traps of India are often called traps, after the Swedish word trappa, due to the characteristic stairstep geomorphology of many associated landscapes.
Volcanic activity is a major part of the geology of Canada and is characterized by many types of volcanic landform, including lava flows, volcanic plateaus, lava domes, cinder cones, stratovolcanoes, shield volcanoes, submarine volcanoes, calderas, diatremes, and maars, along with less common volcanic forms such as tuyas and subglacial mounds.
The geology of the Pacific Northwest includes the composition, structure, physical properties and the processes that shape the Pacific Northwest region of North America. The region is part of the Ring of Fire: the subduction of the Pacific and Farallon Plates under the North American Plate is responsible for many of the area's scenic features as well as some of its hazards, such as volcanoes, earthquakes, and landslides.
A volcanic dam is a type of natural dam produced directly or indirectly by volcanism, which holds or temporarily restricts the flow of surface water in existing streams, like a man-made dam. There are two main types of volcanic dams, those created by the flow of molten lava, and those created by the primary or secondary deposition of pyroclastic material and debris. This classification generally excludes other, often larger and longer lived dam-type geologic features, separately termed crater lakes, although these volcanic centers may be associated with the source of material for volcanic dams, and the lowest portion of its confining rim may be considered as such a dam, especially if the lake level within the crater is relatively high.
The Faroe or Faeroe Islands, or simply the Faroes, is a North Atlantic island group and an autonomous territory of the Kingdom of Denmark.
The North Atlantic Igneous Province (NAIP) is a large igneous province in the North Atlantic, centered on Iceland. In the Paleogene, the province formed the Thulean Plateau, a large basaltic lava plain, which extended over at least 1.3 million km2 (500 thousand sq mi) in area and 6.6 million km3 (1.6 million cu mi) in volume. The plateau was broken up during the opening of the North Atlantic Ocean leaving remnants preserved in north Ireland, west Scotland, the Faroe Islands, northwest Iceland, east Greenland, western Norway and many of the islands located in the north eastern portion of the North Atlantic Ocean. The igneous province is the origin of the Giant's Causeway and Fingal's Cave. The province is also known as Brito–Arctic province and the portion of the province in the British Isles is also called the British Tertiary Volcanic Province or British Tertiary Igneous Province.
Volcanic passive margins (VPM) and non-volcanic passive margins are the two forms of transitional crust that lie beneath passive continental margins that occur on Earth as the result of the formation of ocean basins via continental rifting. Initiation of igneous processes associated with volcanic passive margins occurs before and/or during the rifting process depending on the cause of rifting. There are two accepted models for VPM formation: hotspots/mantle plumes and slab pull. Both result in large, quick lava flows over a relatively short period of geologic time. VPM's progress further as cooling and subsidence begins as the margins give way to formation of normal oceanic crust from the widening rifts.
Nintoku Seamount or Nintoku Guyot is a seamount and guyot in the Hawaiian-Emperor seamount chain. It is a large, irregularly shaped volcano that last erupted 66 million years ago. Three lava flows have been sampled at Nintoku Seamount; the flows are almost all alkalic (subaerial) lava. It is 56.2 million years old.
Volcanism of Northern Canada has produced hundreds of volcanic areas and extensive lava formations across Northern Canada. The region's different volcano and lava types originate from different tectonic settings and types of volcanic eruptions, ranging from passive lava eruptions to violent explosive eruptions. Northern Canada has a record of very large volumes of magmatic rock called large igneous provinces. They are represented by deep-level plumbing systems consisting of giant dike swarms, sill provinces and layered intrusions.
Lava deltas, similar to river deltas, form wherever sufficient sub-aerial flows of lava enter standing bodies of water. The lava cools and breaks up as it encounters the water, with the resulting fragments filling in the adjacent seabed topography such that the flow can move further offshore sub-aerially. Lava deltas are generally associated with large-scale, effusive type basaltic volcanism.
The Cardenas Basalt, also known as either the Cardenas Lava or Cardenas Lavas, is a rock formation that outcrops over an area of about 310 km2 (120 mi2) in the eastern Grand Canyon, Coconino County, Arizona. The lower part of the Cardenas Basalt forms granular talus slopes. Its upper part forms nearly continuous low cliffs that are parallel to the general course of the Colorado River. The most complete, readily accessible, and easily studied exposure of the Cardenas Basalt lies in Basalt Canyon. This is also its type locality.
The Unkar Group is a sequence of strata of Proterozoic age that are subdivided into five geologic formations and exposed within the Grand Canyon, Arizona, Southwestern United States. The 5-unit Unkar Group is the basal member of the 8-member Grand Canyon Supergroup. The Unkar is about 1,600 to 2,200 m thick and composed, in ascending order, of the Bass Formation, Hakatai Shale, Shinumo Quartzite, Dox Formation, and Cardenas Basalt. Units 4 & 5 are found mostly in the eastern region of Grand Canyon. Units 1 through 3 are found in central Grand Canyon. The Unkar Group accumulated approximately between 1250 and 1104 Ma. In ascending order, the Unkar Group is overlain by the Nankoweap Formation, about 113 to 150 m thick; the Chuar Group, about 1,900 m (6,200 ft) thick; and the Sixtymile Formation, about 60 m (200 ft) thick. These are all of the units of the Grand Canyon Supergroup. The Unkar Group makes up approximately half of the thickness of the 8-unit Supergroup.
The Geologic history of the Chiricahua Mountains concerns the Chiricahua Mountains, an inactive volcanic range located in Coronado National Forest of southeastern Arizona, in the United States. They are part of an "archipelago" of mountain ranges known as the sky islands that connect the Sierra Madre Occidental in Mexico with the Rocky Mountains. The Chiricahua Mountains are home to a number of unusual geologic features associated with the Turkey Creek Caldera, some of which are protected by Chiricahua National Monument. The landscape has been dominantly shaped by faulting due to Basin and Range extension during the Miocene, volcanic activity, and erosion.
The geology of Guam formed as a result of mafic, felsic and intermediate composition volcanic rocks erupting below the ocean, building up the base of the island in the Eocene, between 33.9 and 56 million years ago. The island emerged above the water in the Eocene, although the volcanic crater collapsed. A second volcanic crater formed on the south of the island in the Oligocene and Miocene. In the shallow water, numerous limestone formations took shape, with thick alternating layers of volcanic material. The second crater collapsed and Guam went through a period in which it was almost entirely submerged, resembling a swampy atoll, until structural deformation slowly uplifted different parts of the island to their present topography. The process of uplift led to widespread erosion and clay formation, as well as the deposition of different types of limestone, reflecting different water depths.
The geology of Saint Helena resulted from the long-running volcanic activity of the Saint Helena hotspot. Most of the island was formed beginning 14 million years ago. Volcanism on the island ceased seven million years ago, leading to long-running erosion and the formation of deep, v-shaped valleys along with steep coastal cliffs. Some geochemists have observed significant trace element variations between South Atlantic islands and proposed that deep-ocean sediments may have mixed into the magma which formed Saint Helena.
