The main focus of most studies of hazards is, not surprisingly their not inconsiderable negative impacts. However, there are certain economic and social benefits to be gained from living in areas of tectonic activity. When students are asked to consider their benefits, they invariably start by saying that 'houses must be cheap because no-one wants to live there..', but clearly people do: over a million people live on the slopes of Mount Vesuvius alone, and others return to their homes on the slopes of Mt. Merapi on Java despite the dangers.
We shall consider the benefits under a series of headings: this information comes from a variety of sources, including the USGS factsheet HERE. For the latest volcanic activity updates go to John Seach's excellent VOLCANO LIVE. They will mention buildings which have been damaged which, by their position on the slopes will give an indication of why they were there e.g ski lifts being damaged will tell you that ski tourism is a feature of some volcanoes e.g Mt. Ruapehu, NZ.
For a large number of people they have to LIVE WITH THE VOLCANO as there is no alternative. See a section on this lower down the page.
Naturally broken aggregate: cinder tracks for athletics; building stone
People have mined gems and metals. Diamonds found in volcanic vents (& opals). Gold, silver, molybdenum, copper, zinc, lead and mercury.
Most of the metallic minerals mined in the world, such as copper, gold, silver, lead, and zinc, are associated with magmas found deep within the roots of extinct volcanoes located above subduction zones. Rising magma does not always reach the surface to erupt; instead it may slowly cool and harden beneath the volcano to form a wide variety of crystalline rocks (generally called plutonic or granitic rocks). Some of the best examples of such deep-seated granitic rocks, later exposed by erosion, are magnificently displayed in California's Yosemite National Park. Ore deposits commonly form around the magma bodies that feed volcanoes because there is a ready supply of heat, which convectively moves and circulates ore-bearing fluids. The metals, originally scattered in trace amounts in magma or surrounding solid rocks, become concentrated by circulating hot fluids and can be redeposited, under favorable temperature and pressure conditions, to form rich mineral veins.
The active volcanic vents along the spreading mid-ocean ridges create ideal environments for the circulation of fluids rich in minerals and for ore deposition. Water as hot as 380 °C gushes out of geothermal springs along the spreading centers. The water has been heated during circulation by contact with the hot volcanic rocks forming the ridge. Deep-sea hot springs containing an abundance of dark-colored ore minerals (sulfides) of iron, copper, zinc, nickel, and other metals are called "black smokers." On rare occasions, such deep-sea ore deposits are later exposed in remnants of ancient oceanic crust that have been scraped off and left ("beached") on top of continental crust during past subduction processes. The Troodos Massif on the Island of Cyprus is perhaps the best known example of such ancient oceanic crust. Cyprus was an important source of copper in the ancient world, and Romans called copper the "Cyprian metal"; the Latin word for copper is cyprium.
Literally 'heat from the Earth': there is a useful GEOTHERMAL SITE here which looks at the way in which the power is generated.
Geothermal energy can be harnessed from the Earth's natural heat associated with active volcanoes or geologically young inactive volcanoes still giving off heat at depth. Steam from high-temperature geothermal fluids can be used to drive turbines and generate electrical power, while lower temperature fluids provide hot water for space-heating purposes, heat for greenhouses and industrial uses, and hot or warm springs at resort spas. For example, geothermal heat warms more than 70 percent of the homes in Iceland, and The Geysers geothermal field in Northern California produces enough electricity to meet the power demands of San Francisco. In addition to being an energy resource, some geo-thermal waters also contain sulfur, gold, silver, and mercury that can be recovered as a byproduct of energy production
The occasional GEO FACTSHEET No. 76 has a useful article on Geothermal energy.
Oil and natural gas are the products of the deep burial and decomposition of accumulated organic material in geologic basins that flank mountain ranges formed by plate-tectonic processes. Heat and pressure at depth transform the decomposed organic material into tiny pockets of gas and liquid petroleum, which then migrate through the pore spaces and larger openings in the surrounding rocks and collect in reservoirs, generally within 5 km of the Earth's surface. Coal is also a product of accumulated decomposed plant debris, later buried and compacted beneath overlying sediments. Most coal originated as peat in ancient swamps created many millions of years ago, associated with the draining and flooding of landmasses caused by changes in sea level related to plate tectonics and other geologic processes. For example, the Appalachian coal deposits formed about 300 million years ago in a low-lying basin that was alternately flooded and drained.
In Reykjavik, Iceland, there are municipal pools (cost £2.50) which are heated by geothermal sources. The famous Blue Lagoon waters are around an hour's drive from the city and have their own BLUE LAGOON website. A free 24-hour geothermally heated pool is located at Nautholsvik beach beach, a mile from the city. (Information courtesy of 'The Times')
People are prepared to take a gamble with a volcano when there is food to be grown. In Indonesia, the fertile soils of Mt. Merapi allow up to 3 crops a year to be grown and harvested.
When volcanic ash weathers it releases minerals into the soil.
Over thousands to millions of years, the physical breakdown and chemical weathering of volcanic rocks have formed some of the most fertile soils on Earth. In tropical, rainy regions, such as the windward (northeastern) side of the Island of Hawaii, the formation of fertile soil and growth of lush vegetation following an eruption can be as fast as a few hundred years. Some of the earliest civilizations (for example, Greek, Etruscan, and Roman) settled on the rich, fertile volcanic soils in the Mediterranean-Aegean region. Some of the best rice-growing regions of Indonesia are in the shadow of active volcanoes. Similarly, many prime agricultural regions in the western United States have fertile soils wholly or largely of volcanic origin.
On the island of Lanzarote, off the W. coast of Africa, the ground is so hot in places that hay left to dry can burst into flames. Farmers spread a 2 inch layer of black lava chips on their fields. These catch the morning dew and fogs and trap the moisture: a mulch. On the same island, a restaurant close to the crater of an active volcano: Timanfaya uses rock at over 600 degrees F to cook the meat.
The moisture retention makes them particuarly useful for viticulture and coffee.
Without preservation by ash, Pompeii is unlikely to have survived as intact as it is today. Preserved some dinosaur remains also, including footprints.
Hydrothermal activity: hot springs, geysers are associated with areas where the crust is thin, for example at Beppu in Japan. (see also earlier notes on Iceland)
Skiing - slopes of Mt. Ruapehu - Key Geography for GCSE 2 Textbook has a good case study on the eruptions of Mt. Ruapehu and the disruption of the pistes by lahars.
Hiking - popular tourist trips up Mt. Kilimanjaro, Mt. St. Helens, Yellowstone National Park.
Crater Lake National Park in USA.
Pumice stones - found in bathrooms for removing hard skin, or in facial pads.
Drilling mud for oil wells - a volcanic clay called BENTONITE
Cat litter - absorbent minerals.
Clay filler for bread products
Stone used to 'stone-wash' jeans, as it is abrasive.
Sulphur is mined from fumaroles. This is a poorly paid occupation, as was made clear in a Discovery Channel documentary. There is also an excellent site on the volcanoes of Indonesia which features pictures of the sulphur miners struggling up from the crater with baskets full of sulphur.
Volcanic glass shards are used in polishing compounds and as an abrasive in toothpaste and kitchen cleaners for surfaces.
For more, see: TECTONIC BENEFITS PAGE 2. This provides a little more background on certain areas mentioned above.
Millions of people live on the slopes of active volcanoes: it would not be practical to move them all, neither would it be possible to move them away from danger completely. In Japan, for example, someone who had been affected by the Kobe earthquake would be unlikely to move to Tokyo to feel safe as there is just as high a risk of earthquakes there.
On the slopes of Mt. Merapi in Java, Indonesia live over 30 000 people. They live there for a number of reasons:
they have lived there all their lives and see no reason to move
they are fatalistic about taking their chances, and believe that sacrifices by shamans will appease the volcano and keep them safe
if they moved to another part of Java they would still be near an active volcano as there are over 30 on the island
the island is very densely populated
the people who live on the slopes are farmers who benefit from the very fertile soils produced by the weathered volcanic ash (See above) - this means that any area they are moved to is unlikely to have soil which is as productive
the people who live on the slopes of the volcano have developed skills which are relevant to their location - these include the terracing of the slopes to produce flat padi fields which can be flooded for the growing of rice (the staple crop) - which presumably means you can attach displays to your classroom wall with it...
people are reluctant to leave friends and family in the area: "we were born here, and we'll die here..."
There is further useful information on the volcano in the Channel 4 programme from the 'Geographical Eye over Asia series'. This features a village called TURGO. The village was affected by the eruption of 1994, which killed 60 people in the village. As a result of this, the local authority declared Turgo uninhabitable, which meant that if people did want to return they would find they were without the usual amenities such as electricity.
There is a useful source of information on how villages on the slopes of INDONESIAN volcanoes have increased their preparedness at the site of the Asian Disaster Preparedness Centre, or ADPC
There are several site-specific hazards in Indonesia.
Ash falls: these can lead to eye irritation, coughing, diarrhoea and flu symptoms, which can be slightly alleviated by the distribution of face masks.
Lahars: heavy rains which fall in Indonesia turn ash deposits into a deadly fast-flowing slurry of ash and boulders which damages buildings and covers crops. It can also disrupt communications.
Mount Ruapehu and the volcanoes in the area such as Tongariro were used by Peter Jackson as the location for Mount Doom and Mordor in the Lord of the Rings trilogy.
Mount Ruapehu is covered by the usual sites such as VOLCANO WORLD. Filming was carried out on the Whakapapa Ski Field and the Turoa Ski Field.
There are some materials available at the Visitor Centre: Ohakune.
These include TOPO ONLINE and LEADING ATTRACTIONS.
Try also RUAPEHU.NZ
Various businesses have sprung up such as HOBBITON TOURS.
In some sensitive areas where filming took place, a carpet was laid down to protect the sensitive areas from the footprints of the film crews and actors: orcs and elves.
Isengard was filmed in Glenorchy.
Visit FIORDLAND. I'll be there some day.
ICELAND: a country on 2 continents
For some very useful photo stories enquiries with photo clips and videos, go to the recently produced site by Chris Durbin. This followed the recent SLN trip to Iceland.
The index page for the new materials is HERE.
This is an excellent mini site which answers lots of questions about Iceland and provides some useful images of case study areas which are free to use within an educational context. Some sections I particularly like include the slow disintegration of a rock, and images of glacial features. There are views across the rift valley of Thingvellir, where the North American plate is slowly moving away from the Eurasian plate, and also the geothermally heated greenhouses at Hveragerdi. Recommended.
