Explain the characteristics and spatial distribution of the following hazards using at least two specific examples. [10 marks]
DURATION
Volcanic eruptions vary in strength and can last anywhere from less than a day to thousands of years. The Stromboli in the Mediterranean, for example, has been erupting for over 2,400 years. An eruption will usually last until the magma has depleted, or until the gas inside the chamber is low enough so that the gas is no longer trying to escape.
Mt. Vesuvius: Extremely varied throughout history
Krakatoa: Extremely varied throughout history
MAGNITUDE
The Volcanic Explosivity Index or VEI is used to measure the intensity of volcanic eruptions. The scale is dependent on how much volcanic material is thrown out, the height of it, and the duration of the activity. Eruptions have 8 classifications, from 0 or non-explosive to 8 or mega-colossal.
Mt. Vesuvius: typically mega-colossal
Krakatoa: typically colossal to mega-colossal
PREDICTABILITY
Volcanoes are difficult to precisely predict but there are usually various warning signs that suggest impending eruptions. Scientists monitor seismicity rates, quake activity, and ground deformation. They are usually able to predict volcanic eruptions weeks in advance, giving local populations sufficient time to evacuate.
Mt. Vesuvius: Constantly monitored due to the unusually high density of surrounding population.
Krakatoa: Early eruptions were not predicted, but current volcanic activity is monitored heavily.
REGULARITY
Volcanoes are typically categorized according to various things like duration, lava flow, cause, magnitude, etc. Some common types of volcanic eruptions include Hawaiian Eruptions, Strombolian Eruptions, Vulcanian Eruptions, Plinian Eruptions, Lava Domes, and Surtseyan Eruptions.
Mt. Vesuvius: Plinian Eruptions
Krakatoa: Plinian Eruption, more recently Strombolian Eruptions
FREQUENCY
Of the 500 or so active volcanoes across the world, around 10 are erupting every day. But for the most part, they are very small, contained, and harmless. From time to time however, we get major eruptions that are large enough to destroy properties and even take lives.
Mt. Vesuvius: Highly active, with multiple historical accounts of catastrophe.
Krakatoa: Very highly active and dangerous with multiple recent minor eruptions, but catastrophic eruptions in history.
SPEED OF ONSET
Although volcanic eruptions can currently be predicted days or even weeks in advance, the onset of the eruption itself varies considerably. They may occur suddenly or gradually.
Mt. Vesuvius: Varies considerably
Krakatoa: Varies considerably
SPATIAL DISTRIBUTION
Volcanoes are found along destructive (convergent) plate boundaries, constructive (divergent) plate boundaries, and at various hot spots in the earth’s surface. The Ring of Fire is a famous volcanic chain that surrounds the Pacific Ocean. More than half of the world’s active volcanoes above sea level are a part of this ring.
Mt. Vesuvius: Gulf of Naples, Italy
Krakatoa: Sunda Strait, Indonesia
Tuesday, January 21, 2014
Sunday, January 19, 2014
Group Work #2 (Kevin, Margret, Dave, Emily) --> Volcanoes and Droughts
Distinguish between two chosen hazards in terms of their spatial extent, predictability, frequency, magnitude, duration, speed of onset and effects. [10 marks]
Volcanoes are found along destructive (convergent) plate boundaries, constructive (divergent) plate boundaries, and at various hot spots in the earth’s surface. The Ring of Fire is a famous volcanic chain that surrounds the Pacific Ocean. More than half of the world’s active volcanoes above sea level are a part of this ring. Droughts, on the other hand, can happen anywhere in dry areas of land and regions, though most of the droughts occur along the equator. Most droughts are found in Australia, Brazil, the Sahel, China and India. There are many reasons as to why droughts occur, but it is mostly because there is very little rainfall. If rainfall does occur, it is absorbed quickly into the ground or it is blown away by the dry airflow along the ground.
Volcanoes are difficult to precisely predict but there are usually various warning signs that suggest impending eruptions. Scientists monitor seismicity rates, quake activity, and ground deformation. They are usually able to predict volcanic eruptions weeks in advance, giving local populations sufficient time to evacuate. Contrariwise, droughts are predictable hazards. The Palmer Drought Severity Index (PDSI) is used by governments and NGOs to measure the supply and demand of water in the area. Based on this model, they figured out that extreme drought occurred at the Western central, Southeastern regions of the country.
Of the 500 or so active volcanoes across the world, around 10 are erupting every day. But for the most part, they are very small, contained, and harmless. From time to time however, we get major eruptions that are large enough to destroy properties and even take lives. The Volcanic Explosivity Index or VEI is used to measure the intensity of volcanic eruptions. The scale is dependent on how much volcanic material is thrown out, the height of it, and the duration of the activity. Eruptions have 8 classifications, from 0 or non-explosive to 8 or mega-colossal. On the other hand, The Standard Precipitation Index (SPI) is used to measure the magnitude. SPI shows that actual precipitation and the compared to the probability of precipitation for different time frames. A drought occurs anytime the SPI is constantly negative, and a drought ends whenever the SPI is positive. Droughts are also a relatively frequent issue. For example, at any given year a drought is occurring somewhere in the United States. Changes in climate have caused draughts and similar events to occur more frequently and violently.
Although volcanic eruptions can currently be predicted days or even weeks in advance, the onset of the eruption itself varies considerably. Volcanic eruptions vary in strength and can last anywhere from less than a day to thousands of years. The Stromboli in the Mediterranean, for example, has been erupting for over 2,400 years. An eruption will usually last until the magma has depleted, or until the gas inside the chamber is low enough so that the gas is no longer trying to escape. On the other hand, the duration of the drought of a drought may differ from place to place. From west to east there is a decreasing pattern in the severity of droughts. The duration of a drought is measured using The Palmer Drought Severity Index (PDSI). PDSI is based on precipitation temperature data and the local Available Water Content (AWC) in the soil. Droughts usually have a slow onset, making it difficult to predict its costs. It nevertheless is a dangerous event that is very difficult to prepare for, and recover from.
Volcanoes are hazardous to wildlife and humans. A large number of people can be killed or displaced, land is destroyed, and the local geographic makeup is altered. These effects of volcanoes are usually obvious and abrupt. Conversely, droughts typically have more long-term and sometimes even unforeseen consequences. Some temporary or permanent impacts of drought include poor soil quality, more wildfires, lower water levels or dried up wetlands, migration of animals, and destruction of habitat. Economic impacts of drought usually include losses of livelihood and changes in market structure due to consequent shortages and surpluses. Social impacts of droughts include deaths, disease, and various health problems.
Volcanoes are found along destructive (convergent) plate boundaries, constructive (divergent) plate boundaries, and at various hot spots in the earth’s surface. The Ring of Fire is a famous volcanic chain that surrounds the Pacific Ocean. More than half of the world’s active volcanoes above sea level are a part of this ring. Droughts, on the other hand, can happen anywhere in dry areas of land and regions, though most of the droughts occur along the equator. Most droughts are found in Australia, Brazil, the Sahel, China and India. There are many reasons as to why droughts occur, but it is mostly because there is very little rainfall. If rainfall does occur, it is absorbed quickly into the ground or it is blown away by the dry airflow along the ground.
Volcanoes are difficult to precisely predict but there are usually various warning signs that suggest impending eruptions. Scientists monitor seismicity rates, quake activity, and ground deformation. They are usually able to predict volcanic eruptions weeks in advance, giving local populations sufficient time to evacuate. Contrariwise, droughts are predictable hazards. The Palmer Drought Severity Index (PDSI) is used by governments and NGOs to measure the supply and demand of water in the area. Based on this model, they figured out that extreme drought occurred at the Western central, Southeastern regions of the country.
Of the 500 or so active volcanoes across the world, around 10 are erupting every day. But for the most part, they are very small, contained, and harmless. From time to time however, we get major eruptions that are large enough to destroy properties and even take lives. The Volcanic Explosivity Index or VEI is used to measure the intensity of volcanic eruptions. The scale is dependent on how much volcanic material is thrown out, the height of it, and the duration of the activity. Eruptions have 8 classifications, from 0 or non-explosive to 8 or mega-colossal. On the other hand, The Standard Precipitation Index (SPI) is used to measure the magnitude. SPI shows that actual precipitation and the compared to the probability of precipitation for different time frames. A drought occurs anytime the SPI is constantly negative, and a drought ends whenever the SPI is positive. Droughts are also a relatively frequent issue. For example, at any given year a drought is occurring somewhere in the United States. Changes in climate have caused draughts and similar events to occur more frequently and violently.
Although volcanic eruptions can currently be predicted days or even weeks in advance, the onset of the eruption itself varies considerably. Volcanic eruptions vary in strength and can last anywhere from less than a day to thousands of years. The Stromboli in the Mediterranean, for example, has been erupting for over 2,400 years. An eruption will usually last until the magma has depleted, or until the gas inside the chamber is low enough so that the gas is no longer trying to escape. On the other hand, the duration of the drought of a drought may differ from place to place. From west to east there is a decreasing pattern in the severity of droughts. The duration of a drought is measured using The Palmer Drought Severity Index (PDSI). PDSI is based on precipitation temperature data and the local Available Water Content (AWC) in the soil. Droughts usually have a slow onset, making it difficult to predict its costs. It nevertheless is a dangerous event that is very difficult to prepare for, and recover from.
Volcanoes are hazardous to wildlife and humans. A large number of people can be killed or displaced, land is destroyed, and the local geographic makeup is altered. These effects of volcanoes are usually obvious and abrupt. Conversely, droughts typically have more long-term and sometimes even unforeseen consequences. Some temporary or permanent impacts of drought include poor soil quality, more wildfires, lower water levels or dried up wetlands, migration of animals, and destruction of habitat. Economic impacts of drought usually include losses of livelihood and changes in market structure due to consequent shortages and surpluses. Social impacts of droughts include deaths, disease, and various health problems.
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