Volcanoes Volcanoes are openings in the Earth which allow magma to escape to the surface, where it becomes lava. Stratovolcanoes are cone-shaped, steep mountains. Shield volcanoes are dome/”shield”-shaped volcanoes. Calderas are large depressions in the ground. Mid-ocean ridges are long underwater gaps between divergent tectonic plates, where new crust is created. Volcanoes can be very dangerous upon explosion, emitting steam, gas, dust, rock and volcanic bombs upon eruption. Diagram of a volcano Volcanoes can be active, dormant, or extinct: Active - Dormant Is currently erupting - Inactive currently, but or likely to erupt again could become active Formally defined as a in the future volcano that has Example: Mauna Kea, Hawaii erupted since the last (shield volcano) Extinct - Not expected to erupt in the future. No volcanic activity. Example: Ben Nevis, Scotland (Caldera) glacial period (~10000 years) Example: Mount Etna, Italy (stratovolcano) Last erupted ~4500 years ago. Last erupted ~100000 years ago. Last erupted 2023 Hazardous effects of volcanoes: - Destroy buildings - Destroy crops - Destroy infrastructure - Kill people and animals They do this through: ● The initial blast releases a pyroclastic cloud (fast-moving current of hot gas and volcanic matter) which can knock over buildings, destroy crops and trees, etc. Volcanic bombs (projectiles made of volcanic matter) can cause more localised damage. ● Poisonous gases and particles like sulfur dioxide, hot ash, etc. kill wildlife and people (whether immediately or through long term respiratory damage). ● Lahars are pyroclastic mudflows consisting of a mixture of ash and water, as dense as concrete and flowing at 60mph. It carves its own path and solidifies quickly. ● Landslides often occur on the side of the mountain, and destroy mountain towns. ● Lava flow usually impacts buildings and structures as it happens more slowly, but can completely destroy towns and ecosystems. ● Earthquakes usually of magnitude 3-5 can sometimes occur alongside volcanoes due to the movement of magma, and cause structural damage to buildings. ● Secondary flooding can occur as local bodies of water can fill with debris and mud, leading to flash-flooding. Positive effects of volcanoes: ● Geothermal energy utilises the heat from the earth’s magma to create electricity and heat. 70% of Iceland’s energy supply is geothermal. ● Volcanoes and associated phenomena (like hot springs) draw tourists which create local economies (hotels, restaurants, gift shops) ● Lava contains minerals like gold, silver, diamond, copper and zinc, which can be mined once it has cooled. This is why mining towns sometimes form around volcanoes. ● Volcanic areas often have great soil due to lava containing minerals useful for plant growth. Microorganisms break down rock and volcanic matter and the remaining chemicals (Potash, nitrogen, sulfur) are important for plant growth. Prediction of volcanic activity: - Satellites monitor molten rock and magma accumulation inside volcanoes and can predict eruptions long in advance. Seismometres measure magma movement occurring underground Gas monitoring can detect changes in the rate of emission of certain gases associated with volcanic eruption. Preparation and Response: Hazard maps outline the areas at risk of different phenomena associated with eruptions (mudflows, ashfalls, etc.). They are usually publicly available. At the event of a volcanic eruption: - People are evacuated - Alarms are sounded - Elderly and children are taken to shelters - Army trucks used to transport people away from dangerous areas. - Bulldozers can be used to form rock walls diverting the flow of lava. Helicopters and planes drop water to cool the lava and slow it Bombing and dynamite can also be used to divert flows After-effects: Ash fall contaminates every body of water it reaches, and so people are advised to drink bottled water. People are also advised to stay indoors and to take measures to prevent ash from entering their homes. This ash is heavy and can collapse the roofs of buildings too if not cleared. Travelling can disturb settled ashes which may lead to inhalation of particulate matter and respiratory problems. Usually, there is regular news and a bulletin regarding the pollution.
