Volcano

• A volcano is a point on the earth’s crust where magma forces its way to the surface, and ash and gases may also escape.
• Volcanoes occur on subduction zones, constructive plate boundaries, and hot spots.
• Magma is the mixture of molten rock, suspended mineral grains and dissolved gases that forms in the crust or mantle when temperature are sufficiently high.
• Basaltic magma contains about 50% SiO2 and very little dissolved gas, and the two common igneous rock derived from basaltic magma are basalt and gabbro.
• Andesitic magma contains about 60% SiO2, a lot of dissolved gas, andesite and diorite are the common IR, and rhyolithic magma contains about 70% SiO2 and the highest gas content.
• The two common igneous rock derived from rhyolithic magma are rhyolite and granite.
• Cinder cones are the simplest type of volcano, with cinders falling around the vent to form a circle or oval cone.
• Composite volcanoes are steep-sided, symmetrical cones.
• Shield volcanoes have a sloping dome shape like a warrior’s shield.
• Calderas are collapsed volcanoes where a magma chamber has emptied and the ground has sunk, often becoming a lake.
• New volcanoes can form, or pressure can build from below, lifting the ground.
• If acidic, a caldera can cause a catastrophic eruption in the form of a “super-volcano”.
• Caldera at Santorini destroyed the Minoan civilization due to tsunamis circa 1600BC.
• Yellowstone is a hotspot.
• Hotspots are tectonic plate movements over a magma plume, occasionally erupting, creating a volcano.
• Hotspots include Hawaii, which is basic, and Yellowstone, which is acid.
• Major hotspots include Yellowstone, Hawaii, and Iceland.
• Vesuvius is located in southern Italy near Naples, is a composite volcano (strato-volcano), has a height (elevation) of 1,281 metres (4,203 ft) above sea level, has a collapsed caldera from a previous eruption, and was formed at the collision of two tectonic plates – the African and the Eurasian.
• Vesuvius has a history of eruptions including 1800 BC – destruction of Bronze age settlements, 79 AD – destruction of Pompeii, and at least 40 times until the last eruption in 1944.
• Pompeii AD79 was a massive eruption of Vesuvius that buried the towns of Pompeii under a thick layer of burning ashes and pumice up to 2.8 metres deep and Herculaneum under 23 metres of ash and pumice, lasted for two days, and resulted in unknown number of deaths.
• Causes of deaths in Pompeii AD79 included burial under ash and pumice, being killed by pyroclastic flows, collapsing buildings, and being hit by lava bombs.
• Canlaon Volcano is a large stratovolcano located in the North Central portion of Negros Island, with an elevation of 2,435 m and a basal diameter of 30 km, and the earliest record of its eruption dates back to 1866 and the latest in 1988.
• Hibok-Hibok Volcano is located at the North Western end of Camiguin Island and had its latest eruption started in September 1948 and lasted till 1953.
• Bulusan Volcano is located in the Eastern portion of Albay about 300 km from Manila and is the most active volcano in the Philippines, reaching up to 2,462 m above sea level and encompassing the towns of Camalig, Malilipot and Sto. Domingo.
• Mayon Volcano is an active volcano located in the Philippines, known for its near-perfect cone shape, and is the subject of numerous myths and legends.
• Pinatubo Volcano is a part of chain volcanoes which border the Western side of Luzon and lies in the Central portion of Zambales Range, towers about 1,745 m above the sea level, and holds the records of the most violent and destructive eruptions in the country.
• Lahars occur on high volcanos covered in snow and ice, or wet mud/soil, and are caused by an eruption, which causes snow to melt or lava to mix with mud, flows downhill like wet concrete.
• Mount Vesuvius is an active volcano in Italy, the only volcano on the European mainland to have erupted in the last 100 years, and is not currently erupting, it is dormant, not extinct.
• Ash clouds are slow moving, the weight of ash can collapse buildings, destroy crops, pollute water, affect air traffic, and enter high atmosphere and cause cooling, disrupting climate.
• Landslide, also called landslip, is the movement of rock, debris or earth down a slope.
• Lava bombs are molten rocks thrown out of a volcano, pumice are smaller rocks that travel short distances and can start fires.
• Reducing the risks from Vesuvius includes round-the-clock monitoring of the volcano, identifying hazard areas, and creating an evacuation plan.
• Highly fertile soils, soft rocks and high mineral content are reasons why people live near a volcano.
• The Decade Volcanoes are 16 volcanoes identified as potentially highly hazardous to humankind.
• Monitoring seismic disturbances, changes in volcano profile, chemical changes in groundwater, and emissions of gases are ways to predict volcanic eruptions.
• Taal Volcano is the world’s lowest volcano located near the center of Taal lake in Batangas City, with the highest point at 311 m and a crater covering area of 235 sq.km, surrounded by fresh body of water, composed of 35 identified cones combined by several eruptions, about 47 craters, and claimed a toll of 1,034 lives in the 1911 eruption.
• Poverty, cheap marginal land, overcrowding and population pressure are reasons why people live near a volcano.
• Most hazards during eruptions are caused by what comes out of a volcano.
• Lava flows are mostly associated with basic volcanos and are slow moving, low risk to human life, cover large areas and destroy large amounts of infrastructure.
• Pyroclastic flows are hot clouds of ash and gas that move downhill, close to the ground, following valleys, high speed up to 500 kmh, up to 30 km, up to 700°C, highly dangerous.