Some of the hazards of volcanoes are the eruptions and ashes.  When volcanoes explode they release gases that are very harmful if inhaled.  Other hazards are the volcanic earthquakes.  The eruptions can destroy a lot just from a volcanic earthquake.  Lava flows are another type of hazard, but it is not as bad as ashes or eruptions.

    The cause of an eruption is the pressure that is built up.  The volcanic eruption can change the weather too.  It can turn it cold just a little bit.  It can also have an affect on weather for a few years.  Another cause of an eruption would be the gases being pressured up, like a balloon, and then suddenly erupts.

    The volcanoes can give lots of different signs that it will erupt soon.  One of the signs would be the magma raising.  You can feel many little earthquakes and that is a sign that a n eruption is coming.  There may also be some frequent steam coming from around the volcano.  Swelling can also mean that there is an eruption going to occur very recently.