Volcanoes Flashcards

Question

What are fissure eruptions?

Answer 1

when 2 plates move apart, lava may be ejected through fissures rather than via a central vent. These can create extensive lava plateaus – flat, featureless basalt plains. These gentler eruptions result in large scale landscaping and are significant contributors to global climate change e.g. Heimay eruption, Iceland.

Answer 2

these are typically found at constructive margins, rift valleys and hot spots. Typically lava flows out of a central vent and can spread over large areas before solidifying. The result is a cone with long, gentle sides made up of layers of lava from repeated flows. Their eruptions are gentle enough to become tourist attractions as in Hawaii and Iceland. e.g. Mauna Loa on Hawaii.

Answer 3

these are typically found at destructive margins and are steep sided convex cones associated with viscous, silica rich gaseous lava that quickly solidifies before running too far down slope. Deadly pyroclastic flows are associated with these volcanoes e.g. Mt Pelee

Answer 4

(strato-volcanoes) are formed from alternating eruptions of tephra and lava, which builds the volcano in layers. These layers produce weaknesses that can be exploited by the magma resulting in secondary cones and fissures. e.g. Mount Etna.

Answer 5

these result when violent eruptions blow off the volcanoes summit. This empties the magma chamber and causes the sides of the volcano to collapse inwards. The resulting vast crater can be many km wide and can be flooded by the sea or fill as a lake. e.g. Krakatoa.

Answer 6

1. The amount of volcanic gas in the air and at ground level - this is a warning sign and can be recorded by gas sampling. 2. Remote satellite analysis and thermal imaging - this can identify changes in and round the main crater 3. Ground deformation - using tiltmeters and laser based electronic distance measurement to detect bulging of the ground caused by rising magma. Slope angles and distance between points can be measured. 4. Ground vibration is measured using seismometers and recorded using seismographs. Micro quakes indicate rising magma fracturing and cracking overlying rock. 5. Water chemistry - Rising magma will both heat groundwater and corrupt it with gases like sulphur, increasing its acidity. Rising groundwater temperature and/or gas content can be measured using hydrological equipment.

Answer 7

Scientists collect data from the instrument networks then analyse them to look for out-of-the-ordinary signals. By comparing the data analysis with similar results from past volcanic events, volcanologists are better able to forecast changes in volcanic activity and determine whether and when a volcano might erupt in the future. These new systems are capable of collecting and transmitting accurate real-time data from the volcano back to Observatory offices, which improves eruption forecasting. It is important that instruments be installed during quiet times when volcanoes are not active so that they are ready to detect the slightest bit of volcanic stirring. Early detection gives the maximum amount of time for people to prepare for an eruption.

Answer 8

Prior to the Mount St. Helens 2004 eruption, monitoring equipment recorded a large increase in earthquake activity. Scientists quickly examined other monitoring data including gas, ground deformation, and satellite imagery to assess if magma or fluid was moving towards the surface. Based on the history of the volcano and the analysis of the monitoring data scientists were able to determine the types of magma could be moving towards the surface This type of knowledge helps scientists figure out the possible types of volcanic activity and the associated hazards to people. Knowing the hazards helps officials determine which real-time warnings are needed to prevent loss of life and property.

Answer 9

Governments do not always respond to scientific predictions and disasters can result. For example, in 1985 despite warnings of an impending eruption with associated lahars, the government of Colombia failed to order an evacuation and 25,000 people lost their lives in the town of Armero when the volcano Nevado del Ruiz erupted. Equally, Scientists do not always get it right and sometimes eruptions that seem imminent never actually occur. This reduces the scientists’ credibility in the eyes of governments and local people and can cause problems the next time an eruption seems likely.

Answer 10

More than 90% of all gas emitted by volcanoes is water vapour(steam), most of which is heated ground water. Other common volcanic gases are carbon dioxide, sulphur dioxide, hydrogen sulphide, hydrogen, and fluorine. Sulphur dioxide gas can react with water droplets in the atmosphere to create acid rain, which causes corrosion and harms vegetation. Carbon dioxide is heavier than air and can be trapped in low areas in concentrations that are deadly to people and animals. Fluorine, which in high concentrations is toxic, can be adsorbed onto volcanic ash particles that later fall to the ground. The fluorine on the particles can poison livestock grazing on ash-coated grass and also contaminate domestic water supplies.

Answer 11

Magma that oozes onto the Earth’s surface is called lava and forms lava flows. The higher a lava’s content of silica, the less easily it flows. For example, low-silica andesite lava can form fast-moving streams or can spread out in broad thin sheets as much as several miles wide. Since 1983, Kilauea Volcano on the Island of Hawaii has erupted basalt lava flows that have destroyed nearly 200 houses and severed the nearby coastal highway. In contrast, flows of higher silica basalt tend to be thick and sluggish, traveling only short distances from a vent. Dacite and rhyolite lavas often squeeze out of a vent to form irregular mounds called lava domes. Between 1980 and 1986, a dacite lava dome at Mount St. Helens grew to about 1,000 feet high and 3,500 feet across.

Answer 12

High-speed avalanches of hot ash, rock fragments, and gas can move down the sides of a volcano during explosive eruptions or when the steep side of a growing lava dome collapses and breaks apart. These pyroclastic flows can be as hot as 1,500°F and move at speeds of 100 to 150 miles per hour. Such flows tend to follow valleys and are capable of knocking down and burning everything in their paths. Lower-density pyroclastic flows, called pyroclastic surges, can easily overflow ridges hundreds of feet high.

Answer 13

A landslide or debris avalanche is a rapid downhill movement of rocky material, snow, and (or) ice. Volcano landslides range in size from small movements of loose debris on the surface of a volcano to massive collapses of the entire summit or sides of a volcano. Steep volcanoes are susceptible to landslides because they are built up partly of layers of loose volcanic rock fragments. Some rocks on volcanoes have also been altered to soft, slippery clay minerals by circulating hot, acidic ground water. Landslides on volcano slopes are triggered when eruptions, heavy rainfall, or large earthquakes cause these materials to break free and move downhill.

Answer 14

Melted snow and ice as a result of the eruption combined with volcanic ash forms mud flows that can move down the course of river valleys at high speeds - 1985 a lahar destroyed the colombian town of Armero after Nevado del Ruiz eruption, only a quarter of the population survived

Answer 15

Ash - little effect on atmosphere HOWEVER Volcanic gases like sulphur dioxide can cause global cooling, while volcanic carbon dioxide, a greenhouse gas, has the potential to promote global warming. The most significant climate impacts from volcanic injections into the stratosphere come from the conversion of sulphur dioxide to sulphuric acid, which condenses rapidly in the stratosphere to form fine sulphate aerosols. The aerosols increase the reflection of radiation from the Sun back into space, cooling the Earth's lower atmosphere or troposphere.

Answer 16

No Carbon dioxide is a greenhouse gas and is the primary gas blamed for climate change. While sulphur dioxide released in contemporary volcanic eruptions has occasionally caused detectable global cooling of the lower atmosphere, the carbon dioxide released in contemporary volcanic eruptions has never caused detectable global warming of the atmosphere.

Answer 17

Acid rain contains a pH of less than 4 and is produced by rain water falling through volcanic emissions. The rain, with a pH between 1.5 and 3.5, has the corrosive property of battery acid. The plume cloud also contains tiny glass fragments that can irritate the eyes and, in rare cases, cause permanent damage. Communities living close to active volcanoes may be affected by drinking acidic rainwater. It may also affect crops.

Answer 18

The Icelandic volcano Eyjafjallajökull exploded to life in 2010 after nearly two centuries of dormancy, spewing out a huge plume of ash that forced widespread flight cancellations for days. The volcano's many eruptions over 10 weeks melted parts of the volcano's icecap, generating more than 140 of the floods.

Answer 19

Sea waves generated by violent volcanic eruptions such as those formed after the eruption of Krakatoa in 1883.

Volcanoes Flashcards

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