Why is andesitic magma dangerous?
Why is andesitic magma dangerous?
Andesite magma can also generate strong explosive eruptions to form pyroclastic flows and surges and enormous eruption columns. Andesites erupt at temperatures between 900 and 1100 ° C.
Are basaltic or andesitic volcanoes more dangerous?
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. In both cases the eruptions are typically driven by the exsolution of volatiles, primarily H2O, CO2, S and halogens.
Why are andesite volcano eruptions explosive and dangerous?
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.
What causes andesitic volcanoes?
Granitic, or rhyolitic, magmas and andesitic magmas are generated at convergent plate boundaries where the oceanic lithosphere (the outer layer of Earth composed of the crust and upper mantle) is subducted so that its edge is positioned below the edge of the continental plate or another oceanic plate.
Are andesitic volcanoes more explosive than basaltic volcanoes?
Lavas and pyroclastics are usually andesitic to rhyolitic in composition. Due to the higher viscosity of magmas erupted from these volcanoes, they are usually more explosive than shield volcanoes.
What is the composition of andesitic magma?
Viscosity of Magmas
| Summary Table | ||
|---|---|---|
| Magma Type | Solidified Rock | Chemical Composition |
| Basaltic | Basalt | 45-55 SiO2 %, high in Fe, Mg, Ca, low in K, Na |
| Andesitic | Andesite | 55-65 SiO2 %, intermediate in Fe, Mg, Ca, Na, K |
| Rhyolitic | Rhyolite | 65-75 SiO2 %, low in Fe, Mg, Ca, high in K, Na. |
What are andesitic volcanoes?
Andesite is a gray to black volcanic rock with intermediate silica content, typical for lava domes and stratovolcanoes in subduction zones. Andesite is an igneous volcanic rock containing between about 52 and 63 weight % silica (SiO2).
What volcano has andesitic magma?
stratovolcanoes
Shield volcanoes are formed by basaltic magma, typically above a mantle plume, whereas the stratovolcanoes (sometimes referred to as composite volcanoes) are formed by andesitic/rhyolitic magma.
Which of the following are reasons why Pyroclastic flows are so dangerous?
A pyroclastic flow is a hot (typically >800 °C, or >1,500 °F ), chaotic mixture of rock fragments, gas, and ash that travels rapidly (tens of meters per second) away from a volcanic vent or collapsing flow front. Pyroclastic flows can be extremely destructive and deadly because of their high temperature and mobility.
What makes a volcano explosive or nonexplosive?
The amount of dissolved gas in the magma provides the driving force for explosive eruptions. The viscosity of the magma, however, is also an important factor in determining whether an eruption will be explosive or nonexplosive.
Why is andesitic lava viscous?
Andesitic lava is an example of a high viscosity lava whereas balastic lava has a low viscosity, so is more runny. High silica content in the andesitic lava contributes to causing this high viscosity and low silica content in the basaltic lava means it is of a lower viscosity.
Is andesitic lava thick or thin?
ANDESITIC LAVA These viscous lavas have relatively high aspect ratios (thickness/area), generally > 1/100, and some are thick enough to form as lava domes. Andesite commonly erupts from stratovolcanoes, where they form small-volume flows that typically advance only short distances down the flanks of a volcano.
Why are andesitic volcanoes generally more dangerous to human societies?
The feedback you provide will help us show you more relevant content in the future. Answer Wiki. Andesitic volcanism is generally more dangerous to human societies because it is more often found on land (as opposed to beneath the sea) and because it is more often explosive (as opposed to effusive).
What is the interior of an andesite volcano composed of?
Although detached blocks occur on the tops of andesite flows, the flow interior is composed of massive lava which grades downward into an autobrecciated (self-fragmented) basal layer. The flow moves by the injection of lobes of lava into the collar of blocky rubble that comprises the flow front.
Why are andesitic magmas more dangerous to humans?
These areas can be populated and expose the people there to volcanic hazards. Andesitic magmas generally have lower densities and higher viscosities than basaltic magmas. These characteristics result in more frequent relatively large explosive eruptive events, which are more hazardous to population centers than effusive lava eruptions.
What is the difference between basalt and andesite lava?
ANDESITIC LAVA. Whereas basalt forms a’a and pahoehoe surface forms, andesite generally produces blocky lava. Here, the surface contains smooth-sided, angular fragments (blocks) that are not as splintery or vesicular as a’a lava fragments. The blocky nature of these flows is attributed to the higher viscosity of andesite.
