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A lava field, sometimes called a lava bed, is a large, mostly flat area of
A lava field, sometimes called a lava bed, is a large, mostly flat area of lava
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...
flows. Such features are generally composed of highly fluid basalt
Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...
lava, and can extend for tens or hundreds of kilometers across the underlying terrain.
Morphology and structure
The final morphology of a lava field can reveal properties such as internal structure, composition, and mechanics of the lava flow when it was fluid. The ridges and patterns on top of the lava field show the direction of thelava channel
A lava channel is a stream of fluid lava contained within zones of static (i.e., solid and stationary) lava or lava levees. The initial channel may not contain levees per se, until the parental flow solidifies over what develops into the channel a ...
s and the often active lava tube
A lava tube, more rarely called a pyroduct, is a 'roofed conduit through which molten lava travels away from its vent'. If lava in the tube drains out, it will leave an empty cave. Lava tubes are common in low-viscosity volcanic systems. La ...
s that may be underneath the solidified "crust." It can also reveal whether the lava flow can be classified as pāhoehoe or 'a'ā. The two main types of lava field structures are defined as sheet flow lava and pillow lava
Pillow lavas are lavas that contain characteristic pillow-shaped structures that are attributed to the extrusion of the lava underwater, or ''subaqueous extrusion''. Pillow lavas in volcanic rock are characterized by thick sequences of discontinu ...
. Sheet flow lava appears like a wrinkled or folded sheet, while pillow lava is bulbous, and often looks like a pile of pillows atop one another.
An important aspect of lava flow morphology is a phenomenon known as lava flow inflation. This occurs in pāhoehoe flows that have a high effusion rate, and initially forms a thin crust atop the lava flow. The fluid lava underneath the crust continues to increase due to the sustained high effusion rate, and thus the entire "structure" increases in size, up to four meters in height. This anomaly can expose important physics and mechanisms behind lava flow that was not previously known.
The structure of lava fields also vary based on geographic location. For example, in subaqueous lava fields, sheet flow lava is found near volcanoes characterized by fast-flowing centers, like the Galapagos Rift, while on the other hand pillow lava fields are found near more slow-flowing centers, like the Mid-Atlantic Ridge
The Mid-Atlantic Ridge is a mid-ocean ridge (a Divergent boundary, divergent or constructive Plate tectonics, plate boundary) located along the floor of the Atlantic Ocean, and part of the List of longest mountain chains on Earth, longest mountai ...
.
Mapping and prediction
The extent of large lava fields is most readily studied from the air or insatellite
A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation ( GPS), broadcasting, scient ...
photos, where their commonly dark, near-black color contrasts sharply with the rest of the landscape. Current computer models are mostly unable to predict the placement of lava fields due to the inability to anticipate random environmental influences. Computer modeling is consistently increasing in quality, but the many micro factors directing lava flow and shape, such as source geometry and lava extrusion rate, limit the accuracy that is currently available.
Notable examples
* Boring Lava Field (United States
The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
)
* Harrat Rahat, which threatened the city of Medina
Medina, officially al-Madinah al-Munawwarah (, ), also known as Taybah () and known in pre-Islamic times as Yathrib (), is the capital of Medina Province (Saudi Arabia), Medina Province in the Hejaz region of western Kingdom of Saudi Arabia, ...
in the 13th century (Saudi Arabia
Saudi Arabia, officially the Kingdom of Saudi Arabia (KSA), is a country in West Asia. Located in the centre of the Middle East, it covers the bulk of the Arabian Peninsula and has a land area of about , making it the List of Asian countries ...
)
* Hell's Half Acre Lava Field (Idaho
Idaho ( ) is a landlocked U.S. state, state in the Pacific Northwest and Mountain states, Mountain West subregions of the Western United States. It borders Montana and Wyoming to the east, Nevada and Utah to the south, and Washington (state), ...
, United States)
*Reykjanes
Reykjanes () is a small headland on the south-western end of the Reykjanes Peninsula in Iceland, giving the main peninsula its name. Volcanic action is responsible for forming the entire peninsula. The nearest town is Keflavik.
The name, , trans ...
, Iceland
Iceland is a Nordic countries, Nordic island country between the Atlantic Ocean, North Atlantic and Arctic Oceans, on the Mid-Atlantic Ridge between North America and Europe. It is culturally and politically linked with Europe and is the regi ...
(peninsula
A peninsula is a landform that extends from a mainland and is only connected to land on one side. Peninsulas exist on each continent. The largest peninsula in the world is the Arabian Peninsula.
Etymology
The word ''peninsula'' derives , . T ...
is mainly a barren waste of lava fields)
*St. George
Saint George (;Geʽez: ጊዮርጊስ, , ka, გიორგი, , , died 23 April 303), also George of Lydda, was an early Christian martyr who is venerated as a saint in Christianity. According to holy tradition, he was a soldier in the ...
, Utah
Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...
, United States
The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
(city built around fields and bluffs covered in lava rocks)
* Mackenzie Large Igneous Province, Canada
Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...
See also
*Volcanic field
A volcanic field is an area of Earth's Earth's crust, crust that is prone to localized volcano, volcanic activity. The type and number of volcanoes required to be called a "field" is not well-defined. Volcanic fields usually consist of clusters ...
*Volcanic plateau
A volcanic plateau is a plateau produced by volcanic activity. There are two main types: lava plateaus and pyroclastic plateaus.
Lava plateau
Lava plateaus are formed by highly fluid basaltic lava during numerous successive eruptions thro ...
* Volcanism of Hawaii
* Volcanism of Iceland
*Volcano
A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.
On Earth, volcanoes are most oft ...
References