Question

Eruptions of shield volcanoes fed by mafic magma tend __.

a) To be explosive
b) To be effusive
c) To be highly viscous
d) To have high silica content

Answer 1

Shield volcanoes fed by mafic magma typically produce effusive eruptions due to the low-viscosity and low silica content of the magma, allowing for a gentle flow of lava rather than violent explosions.

Step-by-step explanation:

Eruptions of shield volcanoes fed by mafic magma tend b) To be effusive.

Mafic magma contains lower levels of silica and has a higher temperature than felsic magma, which makes it less viscous and allows it to flow more easily. Because of its fluidity, when a shield volcano erupts, the mafic lava spreads out in broad, gentle slopes, rather than exploding violently. This spreading out forms the characteristic 'shield' shape from which these volcanoes get their name. In contrast, high silica content would make the magma more viscous, potentially leading to explosive eruptions as seen in stratovolcanoes which are typically fed by felsic magma.

Eruptions with low-viscosity lava enable gases to escape gently, thus avoiding the buildup of pressure that can lead to explosive eruptions. Therefore, the eruptions of shield volcanoes are known to be more effusive, characterized by a steadier and less violent flow of lava onto the surface, creating extensive lava plateaus and gentle volcanic slopes.