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Types of Volcanoes
Volcanoes form in different types depending on the composition of the magma and tectonic setting, with shield volcanoes being non-explosive and forming from basalt in oceanic settings, composite volcanoes sometimes having explosive eruptions from more viscous magma in continental settings, and cinder cones being the smallest from pyroclastic eruptions.
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Types of Volcanoes
- 1. Mrs. Neistadt Physical Science Chapter 29 VOLCANO TYPES
- 2. VOLCANO REVIEW Review Questions: 1. On what kind of plate boundaries do volcanoes appear? 2. What is the difference between magma and lava?
- 3. THREE TYPES OFVOLCANOES: *There are three types of volcanoes: *Shield Volcano *Cinder cone Volcano *Stratovolcano
- 4. *WHY DO WEHAVE DIFFERENT TYPES OF VOLCANOES? The process of magma formation is different at each type of plate boundary. Therefore, the composition of magma differs in each tectonic setting. *Tectonic settings determine the types of volcanoes that form and the types of eruptions that take place.
- 6. *SHIELD VOLCANO Formfrom many layers of “runny” lava. Very wide, not too steep. Biggest type of volcanoes Tallest mountain in the world is Mauna Kea (measures from sea floor to top) non explosive eruptions
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- 8. TECTONIC SETTING (LOCATIONS) Darwin, a shield volcano in the Galapagos Islands. Shield-type volcanoes are almost exclusively located in an oceanic setting, in the “middle” of oceanic basins or as isolated islands, typically somewhat distant from continental shorelines.
- 9. MORPHOLOGY (SHAPE andSIZE) Fernandina, a shield volcano in the Galapagos Islands. Shield volcanoes tend to have very gentle (low-angle) slopes, sometimes referred to as the “overturned soupbowl” profile. Although not as visually dramatic as stratovolcanoes, they are generally much larger, particularly in diameter.
- 10. ACTIVITY Continued; San Martin, a small shield volcano off the coast of Baja, California. These volcanoes can form during single long-term effusive eruptions and remain active for tens to hundreds of thousands of years. During their lifespans, dormant intervals may also last thousands to tens of thousands of years.
- 11. *CINDER CONE VOLCANO Smallest type of volcano Most common Made from pyroclastic material (material shot out of a volcano) Form a large crater Explosive!
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- 13. CINDER CONES Cinder cones,also known as scoria cones, represent the smallest type of volcano, rarely exceeding ~1000 ft in height. They are entirely composed of pyroclastic materials (volcanic ash). They are quite common and associated with both composite or shield volcanoes. They typically occur on the flanks (sides) of these volcanoes where secondary vents or fissures have opened up. Scoria cone near the summit of Mauna Kea, Hawaii. La Poruna, Chile Sunset crater, Arizona
- 14. CINDER CONES A smallcinder cone (~225m high, ~200m in diameter) located on Barren Island, a part of the Andaman Islands chain situated just north of Indonesia.
- 15. CINDER CONES Kwohl Buttecinder cone is one of a chain of small cones trending south of Mt. Bachelor (a composite volcano) in the Cascade range of Oregon. It is ~ 12,000 years old.
- 16. CINDER CONES The CerroNegro cinder cone represents one of Nicaragua’s youngest volcanoes. It was born in April of 1850 and has grown to a height of 250 m.
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- 18. *STRATOVOLCANO OR COMPOSITEVOLCANO: Eruptions alternate between explosive and non-explosive. Sometimes they have runny lava layers, other times the have pyroclastic materials form layers. Have a wide base and steep sides. Have a crater Mount Fuji
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- 20. MORPHOLOGY (SHAPE andSIZE) Mayon, the most active composite volcano in the Philippines. Stratovolcanoes are what most people associate with the word volcano. These towering peaks rise hundreds to several thousand meters above their surroundings, often visually dominating the landscape around them. They tend to be steep-sloped.
- 21. MORPHOLOGY (SHAPE andSIZE) Continued; Niragongo, an active composite volcano located on the border of Rwanda and Zaire, East Africa. The relatively steep profile of stratovolcanoes are due to their rock makeup. They are formed of stratified layers of both viscous lava flows and fragmental material (volcanic ash).
- 22. ACTIVITY Kamen (left) and Kliucheyskoi, two of Kamchatka’s highest composite volcanoes. Due to the viscous nature of the lavas associated with composite volcanoes, they tend to “plug” up. If the pressures are great enough, these volcanoes may literally “blow their top”, and can be quite violent and dangerous!
- 23. ACTIVITY Continued; Colima, Mexico’s most active composite volcano. Some stratovolcanoes may form in a few thousand years, but remain active for tens to hundreds of thousands of years. During their lifespans, dormant intervals may also last tens of thousands of years.
- 24. *2 TYPES OFERUPTIONS *Explosive: volcanoes that build enough pressure to blow its top, sending pyroclastic material into the air. *Non explosive: Build only enough pressure to allow lava to run down its sides.
- 25. NON EXPLOSIVE ERUPTION Mafic: refers to rocks and magma rich in iron and magnesium. This type of lava that is very runny. As magma nears the surface there is little pressure, causing gasses escape easily. Magma low in Silica have quiet eruptions
- 26. EXPLOSIVE ERUPTIONS Felsic:means magma with high silica and feldspar content. Felsic magma traps water and gas bubbles, which leads to lots of pressure. Silica acts like a cork Explosive eruptions are caused by a build up of high pressure. Convergent zones contain lots of water, therefore have explosive eruptions.
- 27. *PYROCLASTIC MATERIALS *Materialthat is thrown into the air during an explosion. *Volcanic bombs: large blobs of magma that harden in the air. Lapilli: pebble size rocks Volcanic ash: tiny powder like material
- 29. *FOUR TYPES OFLAVA Aa: lava that is thick and sharp Pahoehoe: lava that forms thin crust and wrinkles Pillow lava: lava that erupts under water, has a round shape Blocky lava: cooler, lava that does not travel far from eruption, jagged when it dries.
- 30. *AA *lava that is thick and sharp
- 31. *PAHOEHOE: *lava that forms thin crust and wrinkles
- 32. *PILLOW LAVA *lava that erupts under water, has a round shape
- 33. *BLOCKY LAVA *cooler, lava that does not travel far from eruption, jagged when it dries.
- 34. WHY DO COMPOSITEVOLCANOES TEND TO BE EXPLOSIVE AND SHIELD VOLCANOES NON-EXPLOSIVE?? 1) CHEMISTRY (COMPOSITION) OF LAVA 2) LAVA TEMPERATURE COMPOSITE SHIELD - Higher silica content of lavas -Lower silica content of lavas make them more viscous (thick). make them more fluid (runny). - Lava temperatures are - Lava temperatures are quite generally a few hundred degrees hot, ~ 2200oF, making it easier cooler than those of shield for these lavas to “flow like volcanoes, making the lavas water”. “thicker” in consistency.
- 35. OTHER CHARACTERISTICS ASSOCIATED WITH COMPOSITE AND SHIELD VOLCANOES Both volcano types commonly contain abundant gases dissolved in the magma (especially composite-type). GAS EMISSIONS: Water vapor (steam) is the most common gas emitted by a volcano (70-90%). Other common gases include; CO2, CO, SO2, SO, and a variety of other sulfurous (stinky) gases. It is the buildup of gas pressures that commonly cause composite volcanoes to violently explode when they get “plugged up”. ASH EMISSIONS: Pyroclastic (means “hot particle”) eruptions “volcanic ash” are particularly common with composite volcanoes and uncommon with shield volcanoes.
- 36. WHY ARE THESETWO VOLCANO TYPES (COMPOSITE-SHIELD) SO DIFFERENT??? It is most fundamentally tied to the source material from which these two types of volcanoes come from, and this ties back to their tectonic setting!!! Recall, that composite volcanoes primarily have a “continental” setting, and shield volcanoes have an “oceanic” setting.
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- 38. REVIEW 1. What determines the type of volcano found in a particular location? 2. What type of lava creates wrinkled lava flows? 3. What type(s) of volcanoes have the most explosive eruptions?