volcanic hazards

Constructive margins

Balsaltic lava is formed here it is very hot and has low viscocity (very runny) this means it will flow easily and quickly. They are very frequent and go on for a long time but they are not very violent.

Destructive margins

Andesitic lava is formed here they are cooler and more viscous so they flow less easily. They do not erupt as often. However at subduction zones one plate is pulled beneath another melting the plate forming magma which rises to surface as volcanoes as this lava is viscous it forms blockages causing huge pressure build up and a violent eruption.

Pyroclastic flows - gas, ash and volcanic rock that flows fast with little warning.

Lava flows- flows from a volcanic vent typically slow but burns anything in its path.

volcanic gases- gases like carbon dioxide and sulfur dioxide released can be harmful to humans and animals if breathed in.

ash fallout- Heavy ash particles that can damage buildings, kill or injure people and kill vegeation if the ash lands on crops. 

mudflows (Lahars) - when volcanic material mixes with water it can move very fast and travel wide destroying or burying habitats and infrastructure.

acid rain- gases react with water vapour and fall as acid rain damaging ecosystems and casues metal to deteriorate.

Magnitude- volcanic events range from small slow lava flows to huge eruptions. Magnitude of eruptions can be measured from the volcanic explosivity index which grades them from 0-8.

Frequency- How many times it occurs like every 100,00 years or 5 years generally the less frequent the more in magnitude it is.

randomness vs regularity- Some volcanoes erupt at very regular intervals, whereas others may be dormant for hundreds or thousands of years, then erupt several times in quick succession. 

Predictability- The regularity with which a volcano erupts can help scientists predict when it might erupt again. 

Secondary impacts 

Social - People are killed, fires can start due to the lava, mudflows can cause further damage and deaths.

Environmental- Ecosystems can be destroyed due to flow of volcanic material, acid rain can cause acidification of aqautic ecosystems, enhanced greenhouse effects due to the release of gas.

Economic- Eruptions can destroy businesses, ash clouds prevent aircraft flying, damage to buildings can be exspensive to repair, eruptions can attract tourists boosting the economy.

Political- Damage to agricultural land can cause food shortages leading to conflict and political unrest, slows development due to countries having to repair rather than build schools and hospitals etc,.

Short term-

Evacuations, providing emergency suplies like food, water, shelter and medical care.

Long term - 

Prevention- It is not possible to prevent, but you can prevent the risk to people by not developing land next to an active volcano.

Preparedness- Installing monitoring systems, evacuation plans, having an emergency fisrt aid kit, being aware of the nearest emergency shelter, search and rescue teams, fire response units.

Adaptation- strengthen buildings, people can capatilise opportunites by farming or working in a tourist industry.