1. Chapter 12 Section 4 Volcanoes

2. Chapter 12 Section 4 – What You’ll Learn - page 373 Before you read - write the reading’s objectives in this space: 1 – _____________________________________________________________________________________________ 2 – _____________________________________________ ________________________________________________ ________________________________________________ ________________________________________________

3. Chapter 12 Section 4 – What You’ll Learn - page 373 Before you read - write the reading’s objectives in this space: 1 – Describe the types and causes of different volcan 2 – Chapter 12 Section 4 – What You’ll Learn - page 373 Before you read - write the reading’s objectives in this space: 1 – Describe the types and causes of different types of volcanic eruptions 2 – Explain the patterns of occurrence of volcanoes and its link to plate tectonics.

4. What are faults? _________________ What is decompression? _________________ ____________________________________________ Why is decompression important to volcanism? ____________________________________________ 1

5. What are faults? Weaknesses along Earth’s crust where movement takes place. What is decompression? The release of pressure due To movement of fault lines. Why is decompression important to volcanism? Decompression changes (lowers) the melting point of rock. The rock can become liquid at the same temperature.

6. Convection keeps our mantel flowing: Heat Rises Cools, Spreads, and Sinks Cycle Begins Again As fluids heat they Expand becoming less dense And more buoyant. Due to lower density fluids will rise Once fluids rise away from the heat source they cool and sink. As long as there is a heat source the cycle begins again. 2

7. Why does magma rise?__________________________________________________________________ Where does most surface lava occur? _________________________________________ _________________________________________ _________________________________________ _________________________________________ ________________________________________ 3

8. Why does magma rise? Heated rock is less dense causing it to rise. It will surface as long as it has a path to follow (cracks or fissures). Where does most surface lava occur? On or near boundaries of plates and above hot spots

9. What solids erupt from volcanoes? What are Pyroclasts? ___________ ___________________________ Globule or volcanic bomb–________ ___________________________ Ash ________________________ ___________________________ Blocks ____________________ _________________________ Volcanic Bomb – notice rain drop type shape Volcanic Block Volcanic Ash 4

10. What solids erupt from volcanoes? What are Pyroclasts? All solid materials expelled by a volcano. Globule or volcanic bomb– cooled globs of lava (solid material) Ash - dust (smallest particles) falls furthest from source. Blocks – chunks of solid material ripped from the volcano during eruption. Falls closest to source. Volcanic Bomb – notice rain drop type shape Volcanic Block Volcanic Ash

11. What is the most common volcanic gas? __________ What other gases can be expected? ____________ ___________________ All of gasses that are expelled are super heated!! Evidence has shown that volcanoes contribute enough greenhouse gas to affect climate long after the eruption has ended! 5

12. What is the most common volcanic gas? Water vapor What other gases can be expected? Carbon dioxide and sulfur compounds All of gasses that are expelled are super heated!! Evidence has shown that volcanoes contribute enough greenhouse gas to affect climate long after the eruption has ended!

13. The flow looks like ground-hugging grey smoke, but consists of a mixture of poisonous gas, ash, globules, and dense hot lava blocks. Pyroclastic flow – the most dangerous part of a volcano

14. Pyroclastic flow is what covered Pompeii

15. The Tambora volcano in Indonesia erupted in April 1815, but North America and Europe did not notice its effects until months later. In 1816, known as "the year without a summer", gases, ashes and dust arrived over the Iberian Peninsular and reached the stratosphere, where they remained long enough to create "an enormous sun filter". Today Anak (Child of) Krakatau has grown at an average rate of five inches (13 cm) per week Krakatau: The Last Days Pyroclastic Flow Clip

16. What is viscosity? ____________________________ _________________________________________ What is more viscous, water or syrup? ______________ _________________________________________ What affects viscosity? ________________________ _________________________________________ Which tube has the most viscous material? ____________________ 6

17. What is viscosity? A measure of the resistance of a fluid to flow. What is more viscous, water or syrup? Syrup – more resistant to flow. What affects viscosity? Heat, composition, and gas content. Which tube has the most viscous material? Far right

18. Volcanoes erupt in different ways. Viscosity will affect the kind of eruption. Eruptive style is strongly linked to temperature and composition and can be linked to the type of plate boundary associated with it. How will thick magma erupt? _________________ ______________________ How does runny, low silica, high temperature magma erupt? _____________________ 7

19. Volcanoes erupt in different ways. Viscosity will affect the kind of eruption. Eruptive style is strongly linked to temperature and composition and can be linked to the type of plate boundary associated with it. How will thick magma erupt? Cause pressure to build and will explode. How does runny, low silica, high temperature magma erupt? Quiet, free flowing eruptions. Click me

20. Plate Boundary Setting Most of Earth’s volcanoes lie in subduction zones where continental and oceanic materials are being mixed and partially melted. Click me 8

21. What are hot spots? _____________________________________________________________________ Examples include: Hawaii and Yellow Stone National Park Where do scientists think they come from? ____________ __________________________________________ 9

22. What are hot spots? Volcanically active sites that arise in places where large quantities of magma move to the surface in large, column-like plumes. Examples include: Hawaii and Yellow Stone National Park Where do scientists think they come from? Extra heat in the Earth’s mantle.

23. Volcanoes are classified according to their size, shape, and the materials that compose them. Cinder cone volcanoes form ________________________ ___________________________________________ These volcanoes are small. 10

24. Volcanoes are classified according to their size, shape, and the materials that compose them. Cinder cone volcanoes form when the primary eruptive products are large fragments of solid material. These volcanoes are small.

25. Shield volcanoes are _______ and _______ made from ______________of Basaltic lava. 11

26. Shield volcanoes are broad and flat made from many layers of Basaltic lava.

27. Composite volcanoes form from _________________________________________________________________ 12

28. Composite volcanoes form from alternating explosive events that produce pyroclastic materials, and lava flows

29. The figure below compares actual size of average volcanoes

30. Can you match the volcano to it’s type?

31. Section Check Question 1 Where do most volcanoes occur? 13

32. Section Check Question 1 Where do most volcanoes occur? Answer Most volcanoes occur at plate boundaries where huge pieces of the crust pull apart or push together. As a result, the crust often fractures, allowing magma to reach the surface.

33. Section Check Question 2 What type of volcano is formed by an explosive eruption followed by a quiet eruption? A. cinder cone volcano B. composite volcano C. fissure eruption D. shield volcano 14

34. Section Check Question 2 What type of volcano is formed by an explosive eruption followed by a quiet eruption? A. cinder cone volcano B. composite volcano C. fissure eruption D. shield volcano Answer The correct answer is B. Composite volcanoes erupt explosively releasing large quantities of gas and ash. They are followed by quieter eruptions that form a lava layer over the ash.

35. Section Check Question 3 How does a hot spot volcano form? 15

36. Section Check Question 3 How does a hot spot volcano form? Answer A volcano forms above a hot spot when magma erupts through the crust and reaches the surface. Hot spot volcanoes may lie in the middle of plates far from any plate boundaries or near or on plate boundaries. 4 4