What are explosive eruptions associated with?
Explosive eruptions occur where cooler, more viscous magmas (such as andesite) reach the surface. Dissolved gases cannot escape as easily, so pressure may build up until gas explosions blast rock and lava fragments into the air! Lava flows are much more thick and sticky so do not flow downhill as easily.
Which type of volcano is associated with basaltic non explosive eruptions?
Shield volcanoes
Shield volcanoes are composed almost entirely of relatively thin lava flows built up over a central vent. Most shields were formed by low viscosity basaltic magma that flows easily down slope away from the summit vent.
What causes basaltic eruptions?
Because of basalt’s low silica content, it has a low viscosity (resistance to flow). Therefore, basaltic lava can flow quickly and easily move >20 km from a vent. The low viscosity typically allows volcanic gases to escape without generating enormous eruption columns.
Do basaltic volcanoes have explosive eruptions?
Basaltic magmas have lower viscosities, higher temperatures, and lower volatile contents than silicic magmas, and therefore generally have a lower potential for explosive activity. However, basaltic eruptions display great variability, from mild lava flows to more energetic explosions with large plumes.
What is basaltic magma?
Basaltic lava, or mafic lava, is molten rock enriched in iron and magnesium and depleted in silica. Basaltic magmas are formed by exceeding the melting point of the mantle either by adding heat, changing its composition, or decreasing its pressure. Underwater, basaltic lavas are erupted as pillow basalts.
Which two types of volcanoes are associated with the eruption of fluid basaltic lava?
Eruptions of basaltic magma produce shield volcanoes, such as Mauna Loa in Hawaii and cinder cones, such as Sunset Crater in Arizona. Basaltic magma is low in silica and so has a low viscosity, is very fluid, and flows easily.
What is a basaltic eruption?
Basaltic eruptions are the most common form of volcanism on Earth and planetary bodies. The low viscosity of basaltic magmas inhibits fragmentation, which favours effusive and lava-fountaining activity, yet highly explosive, hazardous basaltic eruptions occur.
Why basaltic magma are not explosive?
Eruptions associated with basaltic lava usually are not explosive due to the low silica and gas content. Gases escape more easily when silica content is low. Because of the low viscosity, basaltic lava flows spread out, forming extensive layers.
What kind of volcanic eruption occurs when basaltic magma is present?
There are two major groupings of eruptions: effusive and explosive. Effusive eruption differs from explosive eruption, wherein magma is violently fragmented and rapidly expelled from a volcano. Effusive eruptions are most common in basaltic magmas, but they also occur in intermediate and felsic magmas.
Are basaltic eruptions mild or violent?
Basaltic eruptions often are relatively quiescent, producing lava flows and small strombolian eruptions. On the other hand, andesitic eruptions often are much more violent, sometimes plinian. vesiculation of previously hydrated melts of basaltic, andesitic and dacitic compositions at temperatures reaching 1200 °C.
What are basaltic eruptions?
Why does fragmentation occur in a basaltic eruption?
The low viscosity of basaltic magmas inhibits fragmentation, which favours effusive and lava-fountaining activity, yet highly explosive, hazardous basaltic eruptions occur. The processes that promote fragmentation of basaltic magma remain unclear and are subject to debate.
What makes a magma eruption a highly explosive eruption?
The main process that produces highly explosive activity is brittle magma fragmentation, which is the transition from a continuous liquid phase in which crystals and bubbles are suspended to a continuous gas phase that carries fragments of magma 1, 2.
Which is the most common form of volcanism on Earth?
Basaltic eruptions are the most common form of volcanism on Earth and planetary bodies. The low viscosity of basaltic magmas inhibits fragmentation, which favours effusive and lava-fountaining activity, yet highly explosive, hazardous basaltic eruptions occur.
What are the effects of a supervolcanic eruption?
A supervolcanic super-eruption can cause a small-scale extinction event. E.g. The Toba eruption (Indonesia) triggered a dramatic global winter 74,000 years ago. The volcanic gases that pose the greatest potential hazard to people, animals, agriculture, and property are sulphur dioxide, carbon dioxide, and hydrogen fluoride.