Volcanoes Flashcards
Describe a shield volcano:
Gentle slopes and a wide base, frequent eruptions of basic lava, lava flows at high speeds for long distances before cooling, usually non-violent eruptions, non-viscous lava due ro basaltic composition, found at constructive boundaries, eg. Maura Loa and Kilauea
Describe a composite (strato) volcano:
Steep sides with a distinctive cone shape, high with a narrow base, explosive eruptions of lava and ash, layers of alternating ash and lava, viscous lava builds in layers and does not flow far from the crater, found at destructive boundaries, effusive, secondary or parasitic cones formed when the main vent gets blocked, eg. Mount Etna and Mount St Helens
What are the primary volcanic hazards? <3
Tephra, ash (fallout), pyroclastic flows (nuee ardente), lava flow, volcanic gases
What are the secondary volcanic hazards?
Lábaros, Jokulhlaups, acid rain
What is tephra?
Solid material that is ejected by a volcano, range from ash (less than 2mm in diameter to volcanic rock (more than 64mm)
What is ash fallout?
Large quantities of ash carried by the wind and deposited in the ground, if Dan travel up to thousands of Kms, causes respiratory problems, injuries, damage, deaths and disruption to transport, eg. 2010 E15 eruption in Iceland produced ash cloud that disrupted air travel in Europe
What are pyroclastic flows?
Superheated mixture of gas and tephra that flows at speeds of up to 700Km/h, one of the deadliest volcanic hazards as they can travel long distances and destroy everything in their path, when the fuego erupted in Guatemala in 2018, pyroclastic flows destroyed several nearby towns
What are lava flows?
A flow of magma (now lava) that runs down the surface of a volcano, Lava Flows travel faster on steeper slopes, at higher temperatures, and with lower viscosities, most Lava flows move slowly enough that they are not a risk to Human life, but can cause significant damage to property and infrastructure, the fastest flows and reach speeds of up to 60Mph
• In the 2021 eruption of Mount Nyiragongo, Democratic Republic of the Congo, lava flows travelled almost 10Km destroying properties and killing over 30 People
What are volcanic gases?
Volcanic eruptions can release large quantities of gases such as Sulphur Dioxide (SO2) and
Carbon Dioxide (CO2), These gases are Hazardous to human health causing respiratory problems and deaths, Eg. Kilauea in Hawai (USA) releases large amounts of Sulphur Dioxide (SO2) leading to air quality alerts and health warnings for residents.
What are lahars?
Mudflows that occur when tephra mixes with water, either from rainfall, or from melted snow and ice, they are fast flowing and destroy everything in their path, Eg. The Lahars that occurred when Mount Pinatubo erupted in the Philippines in 1991 caused extensive damage and disruption destroying almost 5000 homes and damaging 70,000, particularly to Angeles City.
What are Jokulhlaups?
Floods caused by a sudden release of water and rockes when galcial ice is melted by an eruption, eg. In 2010 the eruption of Eyjafjallajökull triggered a jökulhlaup which desroyed several bridges and roads, particularly Route 1
What is acid rain?
Any form of precipitation that contains higher-than-normal levels of acidic compounds like nitric acid and sulfuric acid, Forms when Sulfur Dioxide (SOz) emitted during an eruption reacts with water vapour in the atmosphere to form sulfuric acid (HSO4), It can damage crops, forests, vegetation, and Aquatic ecosystems.
What are hotspots?
Areas of volcanic activity that are not related to plate boundaries, Hot magma plumes from the mantle rise and burn through weaker parts of the crust, this can create volcanoes and islands, the plume stays in the same place but the plates continue to move, which can cause chains of islands E.g Hawaii
What percentage of volcanoes are in the ring of fire?
75%
How is vulcanicity measured?
VEI (Volcanic Explosivity Index), the more powerful the more explosive
What are the primary effects of a volcanic eruption?
Environmental - ecosystems damaged through various volcanic hazards, wildlife killed, Economic - businesses and industries destroyed or disrupted, Social - people killed, homes destroyed from lava/pyroclastic flows, Political - government buildings and other important areas destroyed or disrupted
What are the secondary effects of a volcanic eruption?
Environmental - water acidified by acid rain, volcanic gases contribute to greenhouse effect (global warming, Economic - jobs lost, profit from tourism industry lost, Social - fires can start which puts lives at risk, mudflows or floods, trauma, homelessness, Political - conflicts concerning government responses, food shortages, insurance
What is prevention in volcanic hazards?
Can not be prevented, only risk ro people can be prevented by not allowing people near volcanic hazards (preventing building around volcanoes)
What can be done for preparedness in a volcanic eruption?
Monitoring increases the notice of volcanic eruptions, meaning warnings can be given out, education on volcanoes in areas of risk so people what to do if there is a volcanic eruption, evacuation procedures planned, training response teams
What can be done for mitigation in a volcanic eruption?
Ríe tiene intervention to the volcano (concrete blocks to steer lava away from areas at risk), strengthening buildings that are at risk of mudflows or ash pileup, evacuation and exclusion zones, mitigating effects on health by having emergency aid and rescue
What can be done for adaptation in a volcanic eruption?
Move away from areas at risk, capitalise on opportunities such as encouraging tourism, change professions so it is less likely to be affected by volcanic hazards
What is the Wadati-Benioff Zone?
A region of subducting plate, most affected by pressure and friction, where most destructive earthquakes originate
What is a volcanic arc?
A series of volcanoes (often in the shape of an arc) that are formed consecutively as a tectonic plate moves across a magma plume
What is subduction?
Oceanic plate is forced below continental plate due to the oceanic plate being more dense than the continental plate
