A volcano can cause many  horrible things like earthquakes.  They can cause mud slides. Mud slides are very powerful. They can destroy cities.  In Pompeii when a volcano erupted the whole city was covered in lava. During the eruption some people evacuated.  A volcano can cause many avalanches.  While magma is still in the earth's crust it causes cracks on the earth's surface showing the magma.  Mud slides are so powerful they can push boulders over. Avalanches are sometimes made from when a volcano erupts.  Volcanoes can be very dangerous in many ways.

Some things volcanoes do are good.  The Hawaiian islands were formed by volcanoes. If the volcano is an underwater volcano they erupt and form islands.  When the lava cools it forms into a rock called igneous rock .  Sometimes in the igneous rock you can find crystals of many shapes and colors.  Igneous rock is formed from melted rock that has cooled and hardened.  Some of the rocks are called Gabbro, Granite, Rhyolite, Basalt , Pumice, and Obsidian.   In footprints during a mudslide seeds can be protected.  After the mudslide they can sprout out of the footprint.  Very small animals like ants, termites, or ground squirrels can survive from avalanches because they can burrow under ground and are protected.  Birds are smart enough to fly away when they hear or see the mud slides, lava, or avalanches.