Understanding Volcanoes: Explosive Eruptions and Their Effects

1. Volcanoes Liquid Hot Magma. Tungerahua Volcano, Ecuador Picture by Alcinoe Calahorrano

2. Volcano Stats • Definition of Volcano • Mountain that forms when molten rock (magma) is forced to the Earth’s surface • Number of active volcanos= ? • 20 erupting right now(50-60/year) (160/decade) • Number of volcanologists=1,500

3. Volcanic Eruptions Lava flow Lava fountain • Nonexplosive Eruptions • Explosive Eruptions What is Lava? -magma that flows onto the Earth’s surface

4. Volcano Model Demonstration

5. 1. What did you learn? Write/draw this in your science journal. Vents Volcanoes form around vents that release magma onto the Earth’s surface. Lava Magma chamber

6. The Composition of Magma Determines whether it is explosive or not! water • High water content • More likely to be !!! • High content • More likely to be !!! • Why? • Silica has a thick, stiff consistency • Flows slowly • Tends to Harden in the volcano’s vent EXPLOSIVE silica EXPLOSIVE

7. Explosive Volcano Model Demonstration

8. 2. What did you learn? Write/draw this in your science journal. a. What physical event causes explosive eruptions? b. Would high water content increase the likelihood of having an explosive eruption? c. Would high silica content increase the likelihood of having an explosive eruption?

9. What Erupts from a Volcano? Blocky lava Lava can be thick or thin. Pahoehoe Aa Pillow lava

10. Lava Flow Activity

11. Loosen the gelatin volcano from the cups by dipping the cups briefly in the bowl of hot water. • Lay the pegboard on top of a food serving tray to collect drips. • Weave the airline tubing into the pegboard from the top and back up through the bottom so that 2” or so of tubing is sticking up out of the pegboard. Remove the plunger. • Fill the syringe with your prepared “magma.” Remove any air bubbles from the syringe and tubing by holding the syringe upright and squirting out a small amount of the liquid. Air tends to fracture the gelatin. • Unmold the gelatin by tipping the bowl over onto the center of the pegboard on top of the tubing and lifting the bowl. Do this VERY CAREFULLY so that the gelatin cast won’t develop cracks; a few small cracks are acceptable. The gelatin cast will spread and settle. It should resemble a colorless to milky volcano. • Inject the red water VERY SLOWLY, at a rate of about 20 ml/min. Each student should inject about 10mL into the volcano with the other students watching carefully. • What do you observe? • Use a plastic knife to slice open the volcano, and view the cross-section.

12. 3. What did you learn? Write/draw this in your science journal. a. Where did the lava flow in your model? b. Did the lava choose the path of least resistance (weakest places), like cracks? c. Did the lava deepen the existing cracks or make new cracks?

13. What Erupts from a Volcano? • Pyroclastic material • Rock fragments created by eruptions • magma explodes from volcano and solidifies in the air • existing rock is shattered by powerful eruptions EXPLOSIVE Lapilli Volcanic bombs Volcanic blocks Volcanic ash

14. How do volcanoes affect the Earth? • Flows and Fallouts • hot ash can flow really quickly • Knock down buildings • Dam rivers (flooding/drought) • Kill crops and livestock • Climatic Changes • Ash & Gases can block sunlight • Drop average global temperature noticeably

15. Types of Volcanoes Shield volcano Cinder cone volcano Composite volcano

16. Craters, Calderas, and Lava Plateau • Crater • From explosions of material out of the vent and the collapse of material back into vent • Caldera • Much larger depression that forms when magma chamber empties and its roof collapses • Lava Plateau • Forms when lava erupts from long cracks, or fissures, and spreads out evenly (thousands of km)

17. What causes volcanoes? • The Formation of Magma • Mantle rock melts when the temperature increases • or the pressure decreases.

18. What causes volcanoes? • Where Volcanoes Form • Tectonic Plate Boundaries!!! ~75% world’s active volcanoes in Ring of Fire

19. What causes volcanoes?

20. What causes volcanoes? Hot Spots

21. How do volcanologists predict eruptions? • Measuring Small Quakes • Before eruption, increase in number & intensity • Measuring Slope • Bulges may form with magma (tiltmeter) • Measuring Volcanic Gases • Outflow of volcanic gases • Sulfur dioxide, carbon dioxide • Measuring Temperature from Orbit • Measure changes in temperature over time

22. You should not be a Volcanologist if…. • You don’t like hiking, backbacking, rockclimbing, etc. • You are not interested in experiencing extreme temperatures and heights. • If you don’t like to travel to incredible places and see breathtaking views of the world. Robert McGimsey USGS A. Ozerov

23. Eruption Anticipation Activity

24. Place 10mL of baking soda in center of a sheet of bathroom tissue. Fold the corners over the baking soda and crease the edges so that they stay in place. Place the tissue packet in the middle of a large disposable pan. • Put modeling clay around the top edge of a funnel. Turn the funnel upside down over the tissue packet. Press down to make a tight seal. • Put safety goggles on and add 50mL of vinegar and several drops of liquid dish soap to a 200mL beaker, and stir. • Predict how much time will elapse before your volcano erupts. WRITE THIS DOWN! • Pour the liquid into the upturned funnel. Using a stopwatch, record the time you began to pour and the time your volcano erupts. • How close was your prediction?

25. 4. What did you learn? Write/draw this in your science journal. a. Was your time prediction close to the real time of eruption? b. Are the eruption times similar for every group? If not, give at least one reason why this might be. c. How is our experiment different from predicting the eruption of a real volcano?