A lava tube, or pyroduct, [1] is a natural conduit formed by flowing lava from a volcanic vent that moves beneath the hardened surface of a lava flow. If lava in the tube empties, it will leave a cave.
A lava tube, or pyroduct, [1] is a natural conduit formed by flowing lava from a volcanic vent that moves beneath the hardened surface of a lava flow. If lava in the tube empties, it will leave a cave.
A lava tube is a type of lava cave formed when a low-viscosity lava flow develops a continuous and hard crust, which thickens and forms a roof above the still-flowing lava stream. Tubes form in one of two ways: either by the crusting over of lava channels, or from pāhoehoe flows where the lava is moving under the surface. [2]
Lava usually leaves the point of eruption in channels. These channels tend to stay very hot as their surroundings cool. This means they slowly develop walls around them as the surrounding lava cools and/or as the channel melts its way deeper. These channels can get deep enough to crust over, forming an insulating tube that keeps the lava molten and serves as a conduit for the flowing lava. These types of lava tubes tend to be closer to the lava eruption point.
Farther away from the eruption point, lava can flow in an unchanneled, fan-like manner as it leaves its source, which is usually another lava tube leading back to the eruption point. Called pāhoehoe flows, these areas of surface-moving lava cool, forming either a smooth or rough, ropy surface. The lava continues to flow this way until it begins to block its source. At this point, the subsurface lava is still hot enough to break out at a point, and from this point the lava begins as a new "source". Lava flows from the previous source to this breakout point as the surrounding lava of the pāhoehoe flow cools. This forms an underground channel that becomes a lava tube. [3]
A broad lava-flow field often consists of a main lava tube and a series of smaller tubes that supply lava to the front of one or more separate flows. When the supply of lava stops at the end of an eruption or lava is diverted elsewhere, lava in the tube system drains downslope and leaves partially empty caves.
Such drained tubes commonly exhibit step marks on their walls that mark the various depths at which the lava flowed, known as flow ledges or flow lines depending on how prominently they protrude from the walls. Lava tubes generally have pāhoehoe floors, although this may often be covered in breakdown from the ceiling. A variety of speleothems may be found in lava tubes [4] including a variety of stalactite forms generally known as lavacicles, which can be of the splash, "shark tooth", or tubular varieties. Lavacicles are the most common of lava tube speleothems. Drip stalagmites may form under tubular lava stalactites, and the latter may grade into a form known as a tubular lava helictite. A runner is a bead of lava that is extruded from a small opening and then runs down a wall. Lava tubes may also contain mineral deposits that most commonly take the form of crusts or small crystals, and less commonly, as stalactites and stalagmites. Some stalagmites may contain a central conduit and are interpreted as hornitos extruded from the tube floor. [5]
Lava tubes can be up to 14–15 metres (46–49 ft) wide, though are often narrower, and run anywhere from 1–15 metres (3 ft 3 in – 49 ft 3 in) below the surface. Lava tubes can also be extremely long; one tube from the Mauna Loa 1859 flow enters the ocean about 50 kilometers (31 mi) from its eruption point, and the Cueva del Viento–Sobrado system on Teide, Tenerife island, is over 18 kilometers (11 mi) long, due to extensive braided maze areas at the upper zones of the system.
A lava tube system in Kiama, Australia, consists of over 20 tubes, many of which are breakouts of a main lava tube. The largest of these lava tubes is 2 meters (6.6 ft) in diameter and has columnar jointing due to the large cooling surface. Other tubes have concentric and radial jointing features. The tubes are infilled due to the low slope angle of emplacement.
Lunar lava tubes have been discovered [6] and have been studied as possible human habitats, providing natural shielding from radiation. [7]
Martian lava tubes are associated with innumerable lava flows and lava channels on the flanks of Olympus Mons. Partially collapsed lava tubes are visible as chains of pit craters, and broad lava fans formed by lava emerging from intact, subsurface tubes are also common. [8]
Caves, including lava tubes, are considered candidate biotopes of interest for extraterrestrial life. [9]
A stalactite is a mineral formation that hangs from the ceiling of caves, hot springs, or man-made structures such as bridges and mines. Any material that is soluble and that can be deposited as a colloid, or is in suspension, or is capable of being melted, may form a stalactite. Stalactites may be composed of lava, minerals, mud, peat, pitch, sand, sinter, and amberat. A stalactite is not necessarily a speleothem, though speleothems are the most common form of stalactite because of the abundance of limestone caves.
Volcanism, vulcanism or volcanicity is the phenomenon of eruption of molten rock (magma) onto the surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics, and volcanic gases erupt through a break in the surface called a vent. It includes all phenomena resulting from and causing magma within the crust or mantle of the body, to rise through the crust and form volcanic rocks on the surface. Magmas that reach the surface and solidify form extrusive landforms.
A stalagmite is a type of rock formation that rises from the floor of a cave due to the accumulation of material deposited on the floor from ceiling drippings. Stalagmites are typically composed of calcium carbonate, but may consist of lava, mud, peat, pitch, sand, sinter, and amberat.
Lava Beds National Monument is located in northeastern California, in Siskiyou and Modoc counties. The monument lies on the northeastern flank of Medicine Lake Volcano and has the largest total area covered by a volcano in the Cascade Range.
Volcanic cones are among the simplest volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and size of the fragments ejected during the eruption. Types of volcanic cones include stratocones, spatter cones, tuff cones, and cinder cones.
A speleothem is a geological formation by mineral deposits that accumulate over time in natural caves. Speleothems most commonly form in calcareous caves due to carbonate dissolution reactions. They can take a variety of forms, depending on their depositional history and environment. Their chemical composition, gradual growth, and preservation in caves make them useful paleoclimatic proxies.
A soda straw is a speleothem in the form of a hollow mineral cylindrical tube. They are also known as tubular stalactites. Soda straws grow in places where water leaches slowly through cracks in rock, such as on the roofs of caves. Soda straws in caves rarely grow more than a few millimetres per year and may average one tenth of a millimetre per year. A soda straw can turn into a stalactite if the hole at the bottom is blocked, or if the water begins flowing on the outside surface of the hollow tube. Soda straws can also form outside the cave environment on exposed concrete surfaces as a type of calthemite, growing significantly faster than those formed on rock.
Rille is typically used to describe any of the long, narrow depressions in the surface of the Moon that resemble channels. The Latin term is rima, plural rimae. Typically, a rille can be several kilometers wide and hundreds of kilometers in length. However, the term has also been used loosely to describe similar structures on a number of planets in the Solar System, including Mars, Venus, and on a number of moons. All bear a structural resemblance to each other.
A rootless cone, also formerly called a pseudocrater, is a volcanic landform which resembles a true volcanic crater, but differs in that it is not an actual vent from which lava has erupted. They are characterised by the absence of any magma conduit which connects below the surface of a planet.
The Tseax Cone, also called the Tseax River Cone or the Aiyansh Volcano, is a young and active cinder cone and adjacent lava flows associated with the Nass Ranges and the Northern Cordilleran Volcanic Province. It is located east of Crater Creek at outlet of Melita Lake, southeast of Gitlakdamix and 60 kilometres (37 mi) north of Terrace, British Columbia, Canada.
Rimstone, also called gours, is a type of speleothem in the form of a stone dam. Rimstone is made up of calcite and other minerals that build up in cave pools. The formation created, which looks like stairs, often extends into flowstone above or below the original rimstone. Often, rimstone is covered with small, micro-gours on horizontal surfaces. Rimstone basins may form terraces that extend over hundreds of feet, with single basins known up to 200 feet long from Tham Xe Biang Fai in Laos.
A lava cave is any cave formed in volcanic rock, though it typically means caves formed by volcanic processes, which are more properly termed volcanic caves. Sea caves, and other sorts of erosional and crevice caves, may be formed in volcanic rocks, but through non-volcanic processes and usually long after the volcanic rock was emplaced.
Volcanic activity, or volcanism, has played a significant role in the geologic evolution of Mars. Scientists have known since the Mariner 9 mission in 1972 that volcanic features cover large portions of the Martian surface. These features include extensive lava flows, vast lava plains, and the largest known volcanoes in the Solar System. Martian volcanic features range in age from Noachian to late Amazonian, indicating that the planet has been volcanically active throughout its history, and some speculate it probably still is so today. Both Earth and Mars are large, differentiated planets built from similar chondritic materials. Many of the same magmatic processes that occur on Earth also occurred on Mars, and both planets are similar enough compositionally that the same names can be applied to their igneous rocks and minerals.
Surtshellir is a lava cave located in western Iceland, around 60 km from the settlement of Borgarnes. Approximately a mile in length, it is one of the longest such caves in the country. It was the first known lava tube in the world, at least by modern speleologists, and remained the longest known lava tube until the end of the 19th century. While mentioned in the medieval historical-geographical work Landnámabók, Eggert Ólafsson was the first to give a thorough documentation of the cave in his 1750 travels of the region. It is named after the fire giant Surtr, a prominent figure in Norse mythology, who is prophesied to one day engulf the world in the fire of his flaming sword.
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or underwater, usually at temperatures from 800 to 1,200 °C. The volcanic rock resulting from subsequent cooling is also often called lava.
Gruta das Torres, is a lava cave, a geological formation of volcanic origin formed from the flow and cooling of subterranean magma rivers. This formation is located outside the parish of Criação Velha, in the municipality of Madalena, on the western flanks of the island of Pico. The cave system formed from a series of pāhoehoe lava flows which originating from the Cabeço Bravo parasitic cone about 500 to 1500 years ago. The caves are a group of interconnected lava tubes between 0.5–22 metres (2–72 ft) width, created from both pāhoehoe and ʻaʻā types of lavas generated during different geological periods. It has a height between 1.1 and 15 metres (3.6–49 ft) and is located at an elevation of 300 metres (980 ft). With an estimated length of over 5.2 km (3.2 mi) it is the longest lava cave in the Azores. Access to the cave was managed by the Mountaineering Association. Starting in 2011, AZORINA, SA took over the management and organization of the cave.
Martian lava tubes are volcanic caverns on Mars that are believed to form as a result of fast-moving, basaltic lava flows associated with shield volcanism. Lava tubes usually form when the external surface of the lava channels cools more quickly and forms a hardened crust over subsurface lava flows. The flow eventually ceases and drains out of the tube, leaving a conduit-shaped void space which is usually several meters below the surface. Lava tubes are typically associated with extremely fluid pahoehoe lava. Gravity on mars is about 38% that of Earth's, allowing Martian lava tubes to be much larger in comparison.
Grotta del Gelo is a volcanic cave of Mount Etna which is known for the presence of a large amount of ice. The cave formed in 1614–1624 during a large eruption of the volcano, inside one of the lava flows produced during that eruption. Within the two subsequent decades, ice grew and accumulated in the cave. Today it is a tourist destination.
