Explain what happens when volcanoes erupt ppt.pptx

Grade 9 Science Explain what happens when volcanoes erupt ppt.pptx

1. Presented by: CRISTY V. GESTA

2. CONTENT 🠶 Introduction 🠶 Process of volcanic eruption 🠶 Types of volcanic eruption 🠶 Reasons of volcanic eruption 🠶 Effects of volcanic eruption 🠶 Top 10 deadliest volcanic eruption 🠶 Safety tips

3. VOLCANIC ERUPTION 🠶 A volcano is a mountain where lava (hot, liquid rock) comes from a magma chamber under the ground. Most volcanoes have a volcanic crater at the top. When a volcano is active, materials come out of it. The materials include lava, steam, gaseous sulfur compounds, ash and broken rock pieces. 🠶 When there is enough pressure, it causes the volcano to erupt. The pressure blows off the top of the volcano. The magma comes out, sometimes quickly and sometimes slowly.

4. Volcano is mostly a curve along destructive and constructive plate boundaries where Plates push together and drag a path. Cracks or weaknesses allow magnetic rise up from the lowest crust , pressure builds up which then releases something , causing the magma to explode ,called volcanic eruption . Magma reaches to surface is called lava. This molten lava eventually cools to form new rock. PROCESS OF VOLCANIC ERUPTION

5. After more eruption every time magma builds up and form the cone shaped volcano which have the key structure . Collection of magma underneath the volcano forms hot bubbling furnace called magma chamber. The main vent allows this magma to escape and secondary vents are the small holes from which the magma can flow . The caved in surface is called the crater . It created after Eruption blows the top of the volcano. Eruption occurs when pressure forces magma from the chamber up the main vent towards crater .

6. Types Of Volcanic Eruption Strombolian Eruptions Vulcanian Eruptions Plinian Eruptions Pelean Eruptions

7. Strombolian Eruptions 🠶 These are short meters tall. 🠶 Explosive bursts accompanied by booming sounds. 🠶 Caused by bursting gas bubbles.

8. Vulcanian Eruptions 🠶 These are much stronger and more destructive with time. 🠶 Their dome gets damaged. 🠶 Leads to a more continuous lava flow instead of short bursts of lava.

9. Plinian Eruptions 🠶 The most effective of all eruptions 🠶 These eruptions are caused by very viscous magma with a high gas content 🠶 Forming tall columns of gas. 🠶 These eruptions often occur abruptly, remaining inactive for centuries.

10. Pelean Eruptions 🠶 It's major damage comes from landslides of ash flowing slopes at high speeds. 🠶 Plinian Eruption has tall columns of ash and smoke. 🠶 It is almost similar to plinian eruption

11. REASONS There are three dominating theories to explain what causes a volcano to erupt – Due to Density- difference in Magma Pressure of Released Gases Injection of New Magma

12. Due to Density- difference in Magma 🠶 Due to heat and pressure in the Earth's mantle, solid rocks melt, to form magma. Magma has the same mass as the solid rock, but more volume, making it lighter. So, it will attempt to rise, if this magma continues to encounter high- density material till it reaches the Earth's crust, volcanic eruption occurs. It can either be in the form of a lava- flow or may be explosive.

13. Pressure of Released Gases 🠶 magma contains dissolved substances such as water, sulfur dioxide and carbon dioxide. The solubility of magma decreases with the decrease in pressure as it rises up towards the crust, and the gases get released in the form of bubbles. When the volume of the gas bubbles in magma reaches around 75%, magma disintegrates into pyroclasts, a mixture of partially molten and solid fragments. The bursting of pyroclasts is very explosive and the cause of some of the most violent eruptions on the surface of Earth.

14. Injection of New Magma 🠶 when new magma enters a chamber already overflowing with magma, the volcano erupts due to the additional pressure exerted by the injection of new magma. This type of eruption can be placid or violent.

15. EFFECTS Eruptions occurring close to human settlements may destroy lives and property. People often have to be evacuated. Example: Chaparrastique volcano in El Salvador started erupting on 29 Dec,2013. Anyone living within 2 miles of the volcano is evacuated. Ash discharged very high into the stratosphere can have negative consequences on the ozone layer. Ash and mud can mix with rain and melting snow, forming lahars . Lahars are mudflows flowing at very fast velocity. Landscapes and natural sceneries can be destroyed.

16. TOP 10 DEADLIEST VOLCANIC ERUPTIONS MT. TAMBORA, INDONESIA 🠶 Date: April 10 th - 15 th , 1816 🠶 Death toll: 92,000 MT.UNZEN, JAPAN 🠶 Date: 1792 🠶 Death toll: 12,000-15,000 MT.VESUVIUS, ITALY 🠶 Date: August 24 th AD 79 🠶 Death toll: 10,000+ MT. PELEE, WEST INDIES 🠶 Date: April 25 th - May 8 th , 1902 🠶 Death toll: 40,000 MT. KRAKATOA, INDONESIA 🠶 Date: August 16 th - 28 th 1883 🠶 Death toll: 36,000

17. NEVADO DEL RUIZ, COLUMBIA Date: November 13 th , 1985 Death toll: 23,000 THE LAKI VOLCANIC SYSTEM, ICELAND Date: June 8 th 1783- 8 th February 1784 Death toll: 9,350 MT, VESUVIUS, ITALY Date: 1631 Death toll: 6,000 MT. GALUNGGUNG, JAVA INDONESIA Date: 1882 Death toll: 4,011 MT. KELUT, INDONESIA Date: May 19 th , 1919 Death toll: 5,110

18. SAFETY TIPS 🠶 Stay away from active volcanoes. 🠶 If you live near an active volcano, keep goggles and a mask in an emergency kit, along with a flashlight . 🠶 Know your evacuation route. Keep gas in your car 🠶 Before you leave the house, change into long- sleeved shirts and long pants. 🠶 If you are not evacuating, close windows and doors and block chimneys and other vents, to prevent ash from coming into the house.

19. CONCLUSION We need to understand about volcanoes, structure of volcanoes, types of volcanoes to reduce the negative impact of volcano eruptions and take advantage of its benefits on people and environment.Vulcanologists and Geologists conduct research and recommend preventive measures. We must follow the preventive measures to reduce danger to life.

20. REFERENCE 🠶 http://www.buzzle.com/articles/volcanic-eruptions-what- causes- volcanoes-to-erupt.html 🠶 http://eschooltoday.com/volcanoes/effects- of- volcanic- eruptions.html 🠶 http://environment.nationalgeographic.com/envir onment/natural- disasters/volcano- safety- tips/ 🠶 http://www.heritagedaily.com/2014/08/top- 10- deadliest- volcanic- eruptions/104313 🠶 https://en.wikipedia.org/wiki/Volcano