Like the Alaska range, it is part of a system of mountain ranges that extend from Central America to Alaska and Canada. Back The Yukon River flows from western Canada toward the Bering Sea, emptying on the western side of the state, about halfway between the Northern and Southern coasts. It is part of a system of mountain ranges that extend from Central America north to Alaska and Canada. Most of the ridges run from northeast to southwest.
The composition of almost all lava of the Earth's crust is dominated by silicate mineralsmostly feldsparsolivinepyroxenesamphibolesmicas and quartz. Silicate lavas Igneous rocks, which form lava flows when erupted, can be classified into three chemical types: These classes are primarily chemical, however, the chemistry of lava also tends to correlate with the magma temperature, its viscosity and its mode of eruption.
Felsic lava Felsic or silicic lavas such as rhyolite and dacite typically form lava spinesVolcanic landforms domes or "coulees" which are thick, short lava flows and are associated with pyroclastic fragmental deposits.
Most silicic lava flows Volcanic landforms extremely viscous, and typically fragment as they extrude, producing blocky autobreccias.
The high viscosity and strength are the result of their chemistry, which is high in silicaaluminiumpotassiumsodiumand calciumforming a polymerized liquid rich in feldspar and quartz, and thus has a higher viscosity than other magma types. Intermediate lava Intermediate or andesitic lavas are lower in aluminium and silica, and usually somewhat richer in magnesium and iron.
Intermediate lavas form andesite domes and block lavas, and may occur on steep composite volcanoes, such as in the Andes. Greater temperatures tend to destroy polymerized bonds within the magma, promoting more fluid behaviour and also a greater tendency to form phenocrysts.
Higher iron and magnesium tends to manifest as a darker groundmassand also occasionally amphibole or pyroxene phenocrysts. Basaltic magma is high in iron and magnesium, and has relatively lower aluminium and silica, which taken together reduces the degree of polymerization within the melt.
Owing to the higher temperatures, viscosities can be relatively low, although still thousands of times higher than water. The low degree of polymerization and high temperature favors chemical diffusion, so it is common to see large, well-formed phenocrysts within mafic lavas. Basalt lavas tend to produce low-profile shield volcanoes or " flood basalt fields", because the fluidal lava flows for long distances from the vent.
The thickness of a basalt lava, particularly on a low slope, may be much greater than the thickness of the moving lava flow at any one time, because basalt lavas may "inflate" by supply of lava beneath a solidified crust. Underwater, they can form pillow lavaswhich are rather similar to entrail-type pahoehoe lavas on land.
Ultramafic lava Ultramafic lavas such as komatiite and highly magnesian magmas that form boninite take the composition and temperatures of eruptions to the extreme. At this temperature there is no polymerization of the mineral compounds, creating a highly mobile liquid. No modern komatiite lavas are known, as the Earth's mantle has cooled too much to produce highly magnesian magmas.
Unusual lavas Some lavas of unusual composition have erupted onto the surface of the Earth. Carbonatite and natrocarbonatite lavas are known from Ol Doinyo Lengai volcano in Tanzaniawhich is the sole example of an active carbonatite volcano.
The viscosity of lava is important because it determines how the lava will behave. Lavas with high viscosity are rhyolitedaciteandesite and trachytewith cooled basaltic lava also quite viscous; those with low viscosities are freshly erupted basalt, carbonatite and occasionally andesite.
Highly viscous lava shows the following behaviors: However, a degassed viscous lava or one which erupts somewhat hotter than usual may form a lava flow.
Lava with low viscosity shows the following behaviors: Lava flow speeds vary based primarily on viscosity and slope. In general, lava flows slowly 0.
An exceptional speed of 20—60 mph was recorded following the collapse of a lava lake at Mount Nyiragongo. Please help improve this article by adding citations to reliable sources.
Unsourced material may be challenged and removed. February Lava entering the sea to expand the big island of HawaiiHawaii Volcanoes National Park The physical behavior of lava creates the physical forms of a lava flow or volcano. More fluid basaltic lava flows tend to form flat sheet-like bodies, whereas viscous rhyolite lava flows forms knobbly, blocky masses of rock.
General features of volcanology can be used to classify volcanic edifices and provide information on the eruptions which formed the lava flow, even if the sequence of lavas have been buried or metamorphosed.Landforms are categorised by characteristic physical attributes such as elevation, slope, orientation, stratification, rock exposure, and soil type.
7. Dimension 3 DISCIPLINARY CORE IDEAS—EARTH AND SPACE SCIENCES. E arth and space sciences (ESS) investigate processes that operate on Earth and also address its place in the solar system and the galaxy.
Thus ESS involve phenomena that range in scale from the unimaginably large to the invisibly small. Plutonic rocks are hard and erode slowly, so in many places they have become exposed at the surface after the rocks above erode away over millions of years. Cross-section of Agathla volcanic neck, Navajo Volcanic Field, Arizona from Volcano rutadeltambor.com process of exhumation is similar to that for North Berwick Law except that here the volcano last erupted at ~ Ma..
crag and tail. Volcanic Rocks and Associated Landforms Examples of landform features associated with modern and ancient volcanism.
A volcano forms at an site where erupted material builds up (including lava flows, cinders, and ash). In volcanology, a lava dome or volcanic dome is a roughly circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a rutadeltambor.com-building eruptions are common, particularly in convergent plate boundary rutadeltambor.com 6% of eruptions on earth are lava dome forming.
The geochemistry of lava domes can vary from basalt (i.e. Semeru, ) to rhyolite (i.e. Chaiten.