Question

eruptions
write the letter of the correct answer on the line at the left.

1. ___ which of the following is an opening through which molten rock and gas leave a volcano?

a pipe
b magma chamber
c crater
d vent

1. ___ a volcano erupts quietly if its magma is which of the following?

a cool
b solid
c low in silica
d high in silica

1. ___ what do geologists call a volcano that is not likely to erupt ever again?

a extinct
b dormant
c sleeping
d active

1. ___ from what kind of lava does pahoehoe form?

a cool
b runny
c thick
d slow - moving

Explanation:

1. A vent is the opening where molten rock and gas exit a volcano; a pipe is the channel, magma chamber is the storage area, and crater is the depression at the top.
2. Magma low in silica has low viscosity, allowing gases to escape easily, leading to quiet eruptions. High silica magma is thick and causes explosive eruptions.
3. Extinct volcanoes are defined as those not expected to erupt again. Dormant volcanoes may erupt in the future, active ones have erupted recently, and "sleeping" is not a formal geologic term for this category.
4. Pahoehoe is smooth, ropy lava formed from runny (low viscosity, fluid) lava that flows easily and cools into this texture.

Answer:

1. D. vent
2. C. low in silica
3. A. extinct
4. B. runny