Chapter 12 Section 4 Volcanoes

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

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

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

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

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

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

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

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

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

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

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

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

Composite volcanoes form from _________________________________________________________________ 12

Section Check Question 1 Where do most volcanoes occur? 13

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

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