Science 9 Quarter 3; Types of volcano cone shapes.pptx

This presentation discuss the types of volcano cone shapes, and how volcanoes are formed.

1. Types of Volcanoes

2. Lesson Objectives: Describe the basic shapes of volcanoes. Compare the features of volcanoes. Describe the shapes in the formation of volcanoes.

3. Review What are Volcanoes? Volcanoes are openings in the planet’s crust that allow molten rocks (magma) and gasses trapped beneath to escape. The forceful ejection of lava and gasses often result in a relief on the planet’s surface, which appears in the form of a hill or mountain. The resulting structure is what we call a volcano. Note:  The thick blazing hot liquid made up of molten rocks beneath the surface is called magma. When magma reaches the surface, it is called lava.

4. Types of Volcanoes When most people think of volcanoes, they think of a tall mountain with a crater on top, maybe a little snow at the summit and some trees scattered around the base. There are many volcanoes like this, but volcanoes exists in many forms as well. Each type of volcano has characteristic features that distinguish it from other types. Volcanoes differ in appearance because of the composition of their magma and the processes that originally created them. The tall cone shape you usually think of when you think of a volcano describes a composite volcano, one common form of volcanoes. Other types of volcanoes, includes the shield volcanoes include the shield volcano, the cinder cone, fissure volcano , caldera volcano.

5. What Are the Characteristics of Volcanoes? Volcanoes are elevated structures formed due to the magma moving to the surface. Volcanoes can vary in shape but generally consist of a conical structure formed due to the accumulation of erupted material. When magma reaches the surface, it’s called lava. Lava cools down over time and solidifies into rocks. Depending upon the activity, volcanoes can be active, dormant, or extinct. Volcanoes are formed where there is a fracture in Earth’s crust. These fractures allow magma to rise to the ground, pushing rocks and forming volcanoes.

6. What Are the Main Parts of a Volcano? A volcano may seem like a single structure rising above the ground from the outside. However, it consists of several parts, from the top of the opening to the magma chamber inside. Let’s learn about different parts of the volcano in detail.

7. How Does a Volcano Form? Volcano formation is linked with the functioning of tectonic plates. Earth’s crust is not uniform throughout its length –  it consists of layers . The topmost layer is where we live, and beneath it is the mantle. Mantle comprises very hot molten rocks known as magma. The top layer, also known as the tectonic plates, floats over the mantle. These tectonic plates could move towards each other or away from each other. Volcanoes form at the boundaries of these tectonic plates where there are fractures in the Earth’s crust, allowing the magma to escape to the surface.

8. How Does a Volcano Form? The resultant movement of tectonic plates gave rise to two types of plate boundaries; Convergent Plate Boundaries Divergent Plate Boundaries When two tectonic  plates collide with each other , they create convergent plate boundaries. During the collision, the denser plate’s edge is often pushed beneath the less dense plate in a process known as subduction. The edges of the downward-moving plate heat up due to enormous friction, which causes the rocks to melt, forming magma. Pressure build-up forces the magma to move towards the surface and results in an eruption forming a volcano. The  Ring of Fire  in the Pacific lies in the subduction zone and hosts around 425 volcanoes or more.

9. Divergent Plate Boundaries When two plates  move away from each other, they form divergent plate boundaries. Moving plates often result in vents or fissures that give way to magma and allow it to move upward, forming volcanoes. Example: Mount Kilimanjaro in Kenya and Mount Nyiragongo in Congo are located at divergent plate boundaries.

10. Different Types of Volcanoes

11. Depending upon  their shape and formation,  volcanoes can be of six types; Fissure Volcano Shield Volcano Dome Volcano Ash-Cinder Volcano Composite Volcano Caldera Volcano

12. Fissure Volcano Fissure Volcanoes or linear volcanoes are usually found along the oceanic ridges and, in rare cases, on land.

13. Fissure Volcano have no central crater at all giant cracks are open in the ground and expel vast quantities of lava. This lava spreads far and wide to form huge pools that can cover almost everything around. When these pools of lava cool and solidify, the surface remains mostly flat. Majority of these volcanoes are found near the ocean ridges. Example of these is the fissure eruption that occurred in Los Pilas volcano in Nicaragua in 1952 and along Taal volcano.

14. Fissure Volcano They differ from other volcanoes due to their lack of central structure that forms around a crater. Instead, these volcanoes consist of a series of fractures that run deep underground. Lava escaping these volcanoes is of low viscosity; therefore, lateral development of fissure volcanoes is more profound than vertical development. Examples of Fissure Volcanoes:   Eastern African Rift, Cordón Caulle , Holuhraun .

15. Eruption from Hawaii Volcano

16. Iceland

17. Shield Volcano The main characteristic of a shield volcano is its shape of an inverted shield.

18. Shield Has wide gentle slopes. It is low in height Formed by the accumulation of lava that oozes out from the volcano. They look like low, broad, dome shaped mountains. Almost flat like a warrior’s shield. Example: Mt. Biliran in Philippines Mauna Loa Volcano in Hawaii

19. Shield Volcano The height of a shield volcano is much less than its width. Therefore, these volcanoes have low slopes. The lava flow is effusive that is slow-moving due to less viscosity (low in silica). Being less viscous, lava flows to a greater distance before cooling. Accumulation of such a type of lava flow over a long period gives rise to a shield volcano. Examples of Shield Volcano : Mauna Kea, Mauna Loa, Kohala volcano, Killauea , Tamu Massif.

20. Dome Volcano Very thick lava that could not move too far beyond the crater gave rise to the dome volcano.

21. Lava Dome rounded, steep-sided mound is formed by smal , bulging masses of lava Lava coming from a dome is too viscous to flow from the vent, hence, when it cools down and piles up around the vent it solidifies Examples: Unzen Dome in Japan and Novarupta Volcano in Alaska

22. The escaping lava moves sluggishly, cools down and piles around the vent giving the characteristic dome shape to the volcano. Lava domes are typically low in height. Similar to composite volcanoes, they can cause violent eruptions. Examples of Dome Volcanoes:  Mount Merapi, del Caribe volcano, Soufrière Hills and Chaitén lava dome,

23. Cinder Volcano Cinder cone volcanoes typically  rise 300m to 500m  and form by the fragmented and erupted ash that falls near the chimney or vent.

24. Cinder Cone volcano Simplest type of volcanoes Has a single opening Wide crater Has a short and steep slope Composed primarily of loose pyroclastic materials. Are formed from the ejected lava fragment Examples: Taal volcano in the Philippines Mt. Paricutin in Mexico

25. Cinder cone volcanoes  lack horizontal layers , unlike stratovolcanoes. Instead, they form a rather steep conical hill of tephra or pyroclast (volcanic debris). The loose volcanic debris escapes from the vent and collects around it, giving rise to ash-cinder cone volcanoes. Examples of cinder-cone volcanoes : Mono-Inyo Craters, California, Paricutín in Mexico

26. Composite Volcano Composite volcanoes are also known as  strato volcanoes   due to their peculiar characteristics of layers of solidified material.

27. Composite Volcano Also called Stratovolcano It is tall, has wide base and a steep-sided symmetrical cone Sometimes rising 10,000 feet high Composed of ash and cinders. It has a nearly perfect sloped structure-formed from solidified lava and pyroclastic materials. Some of the most beautiful mountains in the world Examples: Mt. Mayon in Bicol and Mt. Vesuvius in Italy

28. They form from consecutive eruptions and lava flow over thousands of years. Composite Volcanoes often have a steep side and very pronounced volcanic cones. Lava coming out of composite volcanoes is usually viscous and sticky due to the greater quantity of silica. It flows slowly and forms a towering structure. Example of Composite Volcano : Pico del Teide, Arenal volcano, Krakatoa, Monte Helena, Monte Vesubio

29. Mayon , also known as Mayon Volcano or Mount Mayon , is an active stratovolcano in the province of Albay in Bicol Region, on the large island of Luzon in the Philippines.

30. Kanlaon , also spelled as Kanla -on or sometimes Canlaon , is an active stratovolcano on the island of Negros, Philippines. It is the highest point in Negros, as well as the whole Visayas, with an elevation of 2,465 m above sea level.

31. Mount Apo is a large solfataric , potentially active stratovolcano in the island of Mindanao, Philippines.

32. Caldera Volcano Caldera is a cauldron-like structure formed when a volcano erupts and creates a depression.

33. Caldera ( Ryolite Caldera Complexes) are the most explosive volcanoes on Earth but they do not look like volcanoes. Their explosions are usually so strong that the volcano will collapse. And when they collapse they create a large caldera. Example: Laguna Caldera

34. When the magma chamber empties following an eruption, the support due to magma vanishes, and the chamber collapses inward, forming calderas. There are resurgent calderas too that form due to refilling of the magma chamber. The refilling magma pushes the caldera floor upward, hence the name, resurgent or ‘rise again.’ Caldera often forms a lake as the depression formed fills with water. Examples of Calderas : Oregon crater lake, Mt Mazama, Kilauea.

35. Crater Lake Caldera:  A satellite view of Crater Lake, one of the world's most famous calderas. Crater Lake formed about 7700 years ago when a massive volcanic eruption of Mount Mazama emptied a large magma chamber below the mountain. The fractured rock above the magma chamber collapsed to produce a massive crater over six miles across. Centuries of rain and snow filled the caldera, creating Crater Lake. With a depth of 1949 feet (594 meters), Crater Lake is the  deepest lake in the United States  and the ninth-deepest lake in the world. The image above was produced using Landsat GeoCover data from NASA.  Enlarge image.

36. What is Volcanic Eruption? The forceful and violent ejection of lava, gasses, and rocks from a volcano is known as a volcanic eruption. The eruptions result from the pressure build-up due to magma moving from the mantle to the magma chamber inside the volcano.

37. How Are Volcanoes Classified? Volcanoes are classified depending upon their activity. By this definition, volcanoes can be; Active Dormant/Inactive Extinct

38. Active Volcanoes These are volcanoes that erupt occasionally. These are volcanoes that erupted with in the last 60O years and those that 10,000 years ago, based on the age of volcanic rocks. Most active volcanoes have erupted in the recent past and have a very high chance of erupting again. Examples of active volcanoes : Mount Etna, Kīlauea , Mount Stromboli, Mt. Mayon

39. Dormant/Inactive Volcanoes These are volcanoes that have no record of eruption for the last 10,000 years . The long period of dormancy is manifested by the weathering and erosion of deep and long valeys . Although dormant volcanoes haven’t erupted for quite a long time, they can explode in the future. Examples:   Mount Fuji (Japan), and Mount Kilimanjaro (Tanzania) Balo Dome in South Cotabato.

40. Extinct Volcanoes It has not erupted or no proof of eruption in historical times. Example: Kyushu-Palau Ridge in the Philippine Sea

41. Extinct Volcanoes Extinct Volcanoes have minimal chance of eruption in the future. A volcano is considered extinct if there has been no eruption for thousands of years. However, there is no guarantee that an extinct volcano may not wake up and become active someday.  Examples:  Mount Thielsen , Oregon, US, and Mount Slemish , Antrim.

42. QUIZ; _____________ are elevated structures in the Earth’s surface, it is formed due to the magma moving to the surface. A type of volcano that has no central crater at all. It looks like a giant cracks open in the ground and expel vast quantities of lava. The simplest type of volcanoes. Has a single opening, wide crater and has a short and steep slope. They look like low, broad, dome shaped mountains. Almost flat like a warrior’s shield. Has wide gentle slopes.

43. What are the Different Types of Volcanic Eruptions? Volcanoes can also be characterized by the kind of eruption that occurs from them. Based on eruptions, volcanoes can be divided into six types; Hawaiian Eruptions Strombolian Eruptions Vulcan-type Eruptions Vesuvian Eruptions Plinian Eruptions Ultra Plinian Eruptions

44. Hawaiian eruptions are characterized by quiet outpourings of lava without strong shocks or explosions. Lava coming out of Hawaiian eruptions is very fluid and could travel kilometers. Gasses trapped in lava are released smoothly; therefore, the lava forms a smooth surface.

45. Volcanoes with Strombolian eruptions are characterized by effusive eruptions forming lava fountains. The Strombolian-type eruptions are regularly and moderately explosive. Lava effusions form layers of solidified material and give rise to stratovolcanoes.

46. Vulcun -type eruptions are marked by violent explosions often destroying the cone they came from. The explosion involves, emission of volcanic bombs, gas clouds, and large quantities of ash. The emissions consist of very viscous lava, rich in silica and large quantities of gas. Vesuvian Eruptions Vesuvian eruptions are similar to Vulcan-type eruptions; however, they are characterized by a very heavy initial explosion that empties the magma chamber completely. The eruptive material can reach 20-25 km in height

47. The name  Plinian eruption  is derived from the Pelée volcano in Martinique, which erupted very violently in 1902. The eruption occurs under a “plug” formed by solidification in the volcanic duct. The magma is very acidic and, therefore, extremely viscous. The eruption is quite explosive, forming a river of expelled materials. Ultra Plinian Eruptions The explosion in Ultra Plinian Eruption exceeds even Plinian eruptions in intensity. The eruption is so explosive it disintegrates the entire volcanic structure. The volume of expelled material is staggering. The escaping gasses could even impact the  global climate .

48. Conclusion Volcanoes are one of the most majestic yet violent structures on a planet. On Earth, different types of volcanoes constantly shape the planet’s surface and depth of the ocean, destroying the old and giving rise to new structures. A gateway connecting the blazing depth of Earth’s mantle to the surface, volcanoes bring essential minerals to the surface, making it possible for life to thrive.