A volcanic eruption is caused by magma (molten rock) moving from
deep in the earth into a magma chamber within the volcano. To
move upward, the magma must push aside rock, creating small
earthquakes. Also, as the magma moves upward from deep within
the earth, the pressure on it lessens so that gases release,
just as removing the cap from a soda bottle releases the gases
dissolved within. Once the magma is in the volcanic chamber, the
additional volume of material may cause the volcano's slopes to
swell. Volcanic eruptions are powerful events, and they are
capable of injecting hydrogen chloride (HCl) high into the
atmosphere. Similarly, oceans produce large volumes of sea salt,
which contains chlorine, on a daily basis. If these compounds
accumulated in large quantities in the stratosphere, they might
produce ozone depletion. When magma is runny, eruptions are
"effusive", which means they ooze lava gently all the time. When
magma is sticky, eruptions are explosive. The magma clogs the
volcano's vent until so m