What are the different types of hazards associated with volcanic eruptions?

The hazards can be categorized into two different types: Primary and Secondary. Of the primary hazards, there are 4 main ones that pose a threat to life and property: lava flows, pyroclastic flows, tephra falls, and gas eruptions. Lava flows are streams of molten magma that has reached the Earth’s surface. Pyroclastic flows are a dense mix of super-heated tephra (all types of ejected material) and poisonous gases moving rapidly down the side of a volcano. Tephra falls are "rains" of volcanic rock and ash that were blasted into the air in volcanic eruptions. Finally, gas eruptions consist of about 80% water vapour, however also contain carbon dioxide and the toxic gas sulfur dioxide, meaning that they are dangerous to human life.
Of the secondary hazards, the more common one encountered in volcanic eruptions is the Lahar, which is a fast-moving stream of rock, mud, volcanic ash and water. This often occurs when a volcano eruption rapidly melts snow and ice, or as a result of heavy rainfall during or after the eruption. The much less common secondary hazard is the Jokulhlaup - a flash flood that occurs when a volcanic eruption melts large portions of a glacier, releasing vast quantities of water from the ice.