Shopping on line can be easy, simple and save you lots of money. It can also take a lot of your time, frustrate you, and result in unwanted purchases. Now the same can be said for regular high street shopping, but with the vast opportunity presented by the Internet it will pay you to spend a few minutes reading this and understanding how to better optimize your Volcano shopping experience:

1. Compare - without doubt the biggest advantage that the Volcano offers shoppers today is the ability to compare thousands of Volcano at a time. This is a great thing, but not necessarily all the time! Too much can be daunting at times so take advantage of the great comparison sites and where possible let them do the hard work for you.

2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about

3. Testimonials - don't know anybody that has bought a Volcano? Wrong! If the Volcano is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.

4. Questions - Got a question about Volcano then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....

5. Reputation - Never heard of the company selling Volcano? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Volcano and build up a picture of their reputation for sales, returns, customer service, delivery etc.

6. Returns - still worried that even after all of the above your Volcano wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.

7. Feedback - happy with your Volcano then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.

8. Security - check for the yellow padlock on the Volcano site before you buy, and the s after http:/ /i.e. https:// = a secure site

9. Contact - got a question about Volcano, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.

10. Payment - ready to pay for your Volcano, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.

{| class="thumbcaption" style="background:transparent;"! colspan="2" | Volcano:|- valign="top"| 1. Large magma chamber2. Bedrock3. Conduit (pipe)4. Base5. Sill6. Branch pipe7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15. Ash cloud|} in the Aleutian Islands of Alaska photographed from the International Space StationA volcano is an opening, or rupture, in a planet's surface or Crust (geology), which allows hot, molten rock, ash and gases to escape from below the surface. Volcanic activity involving the Extrusive (geology) of rock tends to form mountains or features like mountains over a period of time.

Volcanoes are generally found where tectonic plates pull apart or come together. A mid-oceanic ridge, for example the Mid-Atlantic Ridge, has examples of volcanoes caused by "divergent boundary" pulling apart; the Pacific Ring of Fire has examples of volcanoes caused by "convergent boundary" coming together. By contrast, volcanoes are usually not created where two tectonic plates slide past one another. Volcanoes can also form where there is stretching and thinning of the crust (geology) (called "non-hotspot intraplate volcanism"), such as in the African Rift Valley, the Wells Gray-Clearwater Volcanic Field and the Rio Grande Rift in North America and the European Rhine#Geography with its Eifel volcanoes.

Volcanoes can be caused by "mantle plumes". These so-called "hotspot (geology)" , for example at Hawaii, can occur far from plate boundaries. Hotspot volcanoes are also found elsewhere in the solar system, especially on rocky planets and moons.

Divergent plate boundaries At the mid-oceanic ridges, two tectonic plates diverge from one another. New oceanic crust is being formed by hot molten rock slowly cooling and solidifying. The crust is very thin at mid-oceanic ridges due to the pull of the tectonic plates. The release of pressure due to the thinning of the crust leads to Adiabatic process expansion, and the partial melting of the mantle (geology). This melt causes the volcanism and makes the new oceanic crust. Most divergent boundary are at the bottom of the oceans, therefore most volcanic activity is submarine, forming new seafloor. Black smokers are an example of this kind of volcanic activity. Where the mid-oceanic ridge is above sea-level, volcanic islands are formed, for example, Iceland.

Convergent plate boundaries Subduction zones are places where two plates, usually an oceanic plate and a continental plate, collide. In this case, the oceanic plate subducts, or submerges under the continental plate forming a deep ocean trench just offshore. The crust is then melted by the heat from the mantle and becomes magma. This is due to the water content lowering the melting temperature. The magma created here tends to be very viscous due to its high silica content, so often does not reach the surface and cools at depth. When it does reach the surface, a volcano is formed. Typical examples for this kind of volcano are Mount Etna and the volcanoes in the Pacific Ring of Fire.

Hotspots Hotspot (geology) are not usually located on the ridges of tectonic plates, but above mantle plumes, where the convection of Earth's mantle (geology) creates a column of hot material that rises until it reaches the crust, which tends to be thinner than in other areas of the Earth. The temperature of the plume causes the crust to melt and form pipes, which can vent magma. Because the tectonic plates move whereas the mantle plume remains in the same place, each volcano becomes dormant after a while and a new volcano is then formed as the plate shifts over the hotspot. The Hawaiian Islands are thought to be formed in such a manner, as well as the Snake River Plain, with the Yellowstone Caldera being the part of the North American plate currently above the hotspot.

Volcanic features ]The most common perception of a volcano is of a 63%) of silica, the lava is called felsic.

• Felsic lavas (or rhyolites) tend to be highly viscous (not very fluid) and are erupted as domes or short, stubby flows. Viscous lavas tend to form stratovolcanoes or lava domes. Lassen Peak in California is an example of a volcano formed from felsic lava and is actually a large lava dome.
• Because siliceous magmas are so viscous, they tend to trap volatiles (gases) that are present, which cause the magma to erupt catastrophically, eventually forming stratovolcanoes. Pyroclastic flows (ignimbrites) are highly hazardous products of such volcanoes, since they are composed of molten volcanic ash too heavy to go up into the atmosphere, so they hug the volcano's slopes and travel far from their vents during large eruptions. Temperatures as high as 1,200 °C are known to occur in pyroclastic flows, which will incinerate everything flammable in their path and thick layers of hot pyroclastic flow deposits can be laid down, often up to many meters thick. Alaska's Valley of Ten Thousand Smokes, formed by the eruption of Novarupta near Katmai in 1912, is an example of a thick pyroclastic flow or ignimbrite deposit. Volcanic ash that is light enough to be erupted high into the Earth's atmosphere may travel many kilometres before it falls back to ground as a tuff.

If the erupted magma contains 52–63% silica, the lava is of intermediate composition.

• These "Andesite" volcanoes generally only occur above subduction zones (e.g. Mount Merapi, Central Java in Indonesia).

If the erupted magma contains 45% silica, the lava is called mafic (because it contains higher percentages of magnesium (Mg) and iron (Fe)) or basaltic. These lavas are usually much less viscous than rhyolitic lavas, depending on their eruption temperature; they also tend to be hotter than felsic lavas. Mafic lavas occur in a wide range of settings:

• At mid-ocean ridges, where two oceanic Tectonic plates are pulling apart, basaltic lava erupts as Lava#Pillow lava to fill the gap;
• Shield volcanoes (e.g. the Hawaiian Islands, including Mauna Loa and Kilauea), on both oceanic crust and continental crust;
• As Flood basalt.

Some erupted magmas contain

External links

• Smithsonian Institution - Global Volcanism Program
• Volcanic and Geologic Terms from Volcano World
• Volcano Information from the Deep Ocean Exploration Institute, Woods Hole Oceanographic Institution
• Glossary of Volcanic Terms from USGS
• How Volcanoes Work by Tom Harris
• How Volcanoes Work - Educational resource on the science and processes behind volcanoes, intended for university students of geology, volcanology and teachers of earth science.
• Volcano Live - John Seach
• Volcanic Materials Identification
• Natural Disasters - Volcano Great research site for kids.
• Google Video: Erupting Volcano
• Google Maps Plot of World Volcanoes
• University of Washington Libraries: Digital Collections:
• Mount St. Helens Post-Eruption Chemistry Database This collection contains photographs of Mount St. Helens, post-eruption, taken over the span of three years to provide a look at both the human and the scientific sides of studying the eruption of a volcano.
• Mount St. Helens Succession Collection This collection consists of 235 photographs in a study of plant habitats following the May 18, 1980 eruption of Mount St. Helens.
• Volcanic Features of Hawaii and Other Worlds
• National Geographic volcano videos

{| class="thumbcaption" style="background:transparent;"! colspan="2" | Volcano:|- valign="top"| 1. Large magma chamber2. Bedrock3. Conduit (pipe)4. Base5. Sill6. Branch pipe7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15. Ash cloud|} in the Aleutian Islands of Alaska photographed from the International Space StationA volcano is an opening, or rupture, in a planet's surface or Crust (geology), which allows hot, molten rock, ash and gases to escape from below the surface. Volcanic activity involving the Extrusive (geology) of rock tends to form mountains or features like mountains over a period of time.

Volcanoes are generally found where tectonic plates pull apart or come together. A mid-oceanic ridge, for example the Mid-Atlantic Ridge, has examples of volcanoes caused by "divergent boundary" pulling apart; the Pacific Ring of Fire has examples of volcanoes caused by "convergent boundary" coming together. By contrast, volcanoes are usually not created where two tectonic plates slide past one another. Volcanoes can also form where there is stretching and thinning of the crust (geology) (called "non-hotspot intraplate volcanism"), such as in the African Rift Valley, the Wells Gray-Clearwater Volcanic Field and the Rio Grande Rift in North America and the European Rhine#Geography with its Eifel volcanoes.

Volcanoes can be caused by "mantle plumes". These so-called "hotspot (geology)" , for example at Hawaii, can occur far from plate boundaries. Hotspot volcanoes are also found elsewhere in the solar system, especially on rocky planets and moons.

Divergent plate boundaries At the mid-oceanic ridges, two tectonic plates diverge from one another. New oceanic crust is being formed by hot molten rock slowly cooling and solidifying. The crust is very thin at mid-oceanic ridges due to the pull of the tectonic plates. The release of pressure due to the thinning of the crust leads to Adiabatic process expansion, and the partial melting of the mantle (geology). This melt causes the volcanism and makes the new oceanic crust. Most divergent boundary are at the bottom of the oceans, therefore most volcanic activity is submarine, forming new seafloor. Black smokers are an example of this kind of volcanic activity. Where the mid-oceanic ridge is above sea-level, volcanic islands are formed, for example, Iceland.

Convergent plate boundaries Subduction zones are places where two plates, usually an oceanic plate and a continental plate, collide. In this case, the oceanic plate subducts, or submerges under the continental plate forming a deep ocean trench just offshore. The crust is then melted by the heat from the mantle and becomes magma. This is due to the water content lowering the melting temperature. The magma created here tends to be very viscous due to its high silica content, so often does not reach the surface and cools at depth. When it does reach the surface, a volcano is formed. Typical examples for this kind of volcano are Mount Etna and the volcanoes in the Pacific Ring of Fire.

Hotspots Hotspot (geology) are not usually located on the ridges of tectonic plates, but above mantle plumes, where the convection of Earth's mantle (geology) creates a column of hot material that rises until it reaches the crust, which tends to be thinner than in other areas of the Earth. The temperature of the plume causes the crust to melt and form pipes, which can vent magma. Because the tectonic plates move whereas the mantle plume remains in the same place, each volcano becomes dormant after a while and a new volcano is then formed as the plate shifts over the hotspot. The Hawaiian Islands are thought to be formed in such a manner, as well as the Snake River Plain, with the Yellowstone Caldera being the part of the North American plate currently above the hotspot.

Volcanic features ]The most common perception of a volcano is of a 63%) of silica, the lava is called felsic.

• Felsic lavas (or rhyolites) tend to be highly viscous (not very fluid) and are erupted as domes or short, stubby flows. Viscous lavas tend to form stratovolcanoes or lava domes. Lassen Peak in California is an example of a volcano formed from felsic lava and is actually a large lava dome.
• Because siliceous magmas are so viscous, they tend to trap volatiles (gases) that are present, which cause the magma to erupt catastrophically, eventually forming stratovolcanoes. Pyroclastic flows (ignimbrites) are highly hazardous products of such volcanoes, since they are composed of molten volcanic ash too heavy to go up into the atmosphere, so they hug the volcano's slopes and travel far from their vents during large eruptions. Temperatures as high as 1,200 °C are known to occur in pyroclastic flows, which will incinerate everything flammable in their path and thick layers of hot pyroclastic flow deposits can be laid down, often up to many meters thick. Alaska's Valley of Ten Thousand Smokes, formed by the eruption of Novarupta near Katmai in 1912, is an example of a thick pyroclastic flow or ignimbrite deposit. Volcanic ash that is light enough to be erupted high into the Earth's atmosphere may travel many kilometres before it falls back to ground as a tuff.

If the erupted magma contains 52–63% silica, the lava is of intermediate composition.

• These "Andesite" volcanoes generally only occur above subduction zones (e.g. Mount Merapi, Central Java in Indonesia).

If the erupted magma contains 45% silica, the lava is called mafic (because it contains higher percentages of magnesium (Mg) and iron (Fe)) or basaltic. These lavas are usually much less viscous than rhyolitic lavas, depending on their eruption temperature; they also tend to be hotter than felsic lavas. Mafic lavas occur in a wide range of settings:

• At mid-ocean ridges, where two oceanic Tectonic plates are pulling apart, basaltic lava erupts as Lava#Pillow lava to fill the gap;
• Shield volcanoes (e.g. the Hawaiian Islands, including Mauna Loa and Kilauea), on both oceanic crust and continental crust;
• As Flood basalt.

Some erupted magmas contain

External links

• Smithsonian Institution - Global Volcanism Program
• Volcanic and Geologic Terms from Volcano World
• Volcano Information from the Deep Ocean Exploration Institute, Woods Hole Oceanographic Institution
• Glossary of Volcanic Terms from USGS
• How Volcanoes Work by Tom Harris
• How Volcanoes Work - Educational resource on the science and processes behind volcanoes, intended for university students of geology, volcanology and teachers of earth science.
• Volcano Live - John Seach
• Volcanic Materials Identification
• Natural Disasters - Volcano Great research site for kids.
• Google Video: Erupting Volcano
• Google Maps Plot of World Volcanoes
• University of Washington Libraries: Digital Collections:
• Mount St. Helens Post-Eruption Chemistry Database This collection contains photographs of Mount St. Helens, post-eruption, taken over the span of three years to provide a look at both the human and the scientific sides of studying the eruption of a volcano.
• Mount St. Helens Succession Collection This collection consists of 235 photographs in a study of plant habitats following the May 18, 1980 eruption of Mount St. Helens.
• Volcanic Features of Hawaii and Other Worlds
• National Geographic volcano videos

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