Week 2 HSSP Summer 2007
What is a volcano?
Why do volcanoes erupt?
Why volcanoes erupt: Magma has H 2 O and CO 2 gases dissolved in it. These gases form bubbles as the magma rises to the surface and make it erupt Like a opening soda!
May 1980 Mt. St. Helens eruption om/videoplay?docid = &q=Mt.+St.+He lens+1980+eruption +movie&total=17&st art=0&num=10&so= 0&type=search&plin dex=0http://video.google.c om/videoplay?docid = &q=Mt.+St.+He lens+1980+eruption +movie&total=17&st art=0&num=10&so= 0&type=search&plin dex=0
May 1980 Mt. St. Helens eruption
May 1980 Mt. St. Helens eruption
Mt. St. Helens today
Mt. St. Helens today
What comes out of a volcano?
Lava! Lots of different kinds: 1.Ropy lava - Hawaiians call it pahoehoe
What comes out of a volcano? Lava! Lots of different kinds: 1.Ropy lava - Hawaiians call it pahoehoe 2.Sharp lava - Hawaiians call it ‘a’a
What comes out of a volcano? Eruptive cloud: gases - water vapor carbon dioxide nitrogen sulfur dioxide ash - tiny bubbles of magma that freeze when they erupt
What comes out of a volcano? Pyroclastic Flows = hot gas & ash from plume that quickly become heavier than air Yikes!
What comes out of a volcano? Lahars = mud flow (pyroclastic flow + water = mud)
What comes out of a volcano? Volcanic Bombs = lava that cools in the air and becomes aerodynamic (like a football)
What comes out of a volcano? Lots of different products! volcanic bombs pyroclastic flows lahars gas & ash
How is magma formed?
Melting by heating
Decompression melting
Melting due to change in the Solidus
Why do these two eruptions look different? Stratovolcano: More ash, less lava Cone shape volcano Shield Volcano: More lava, less ash Volcano isn’t cone shaped
Because they erupt magma of different: 1) volume 2) viscosity 3) volatile-content (gas) the 3 “V”s
What do these mean? 1) volume 2) viscosity 3) volatile-content the 3 “V”s
Volume Stratovolcano Shield Volcano
What do these mean? 1) volume 2) viscosity 3) volatile-content the 3 “V”s
Viscosity: A measure of how much a fluid resists flowing HIGH VISCOSITY Resists Flowing, Thick, Moves Slowly honey LOW VISCOSITY Flows Easily, Thin, Moves Quickly water
Magma is a liquid made up of different chemical species: SiO 2, MgO, FeO, Al 2 O 3, CaO, K 2 O etc. The amount of each of these chemical species affects the how easily the magma flows More SiO 2 harder to flow (more viscous)
What do these mean? 1) chemical composition 2) viscosity 3) volatile-content the 3 “V”s
Low SiO 2, Low viscosity, Low volatile-content SMALL ERUPTION Shield Volcanoes - example Hawaii
High SiO 2, High viscosity, High volatile-content BIG EXPLOSIVE ERUPTION! Stratovolcanoes - example Mt. St. Helens
Stratovolcanoes vs. Sheild Volcanoes ompeii/interactive/interactive.htmlhttp://dsc.discovery.com/convergence/p ompeii/interactive/interactive.html
There are volcanoes underwater At Mid-ocean ridges
And there are volcanoes on other planets
Volcanoes in our solar systemMars Insert movie: gov/13676/VolcanoCompar e_640x480.mpg ymp.jpg
Venus The Moon Most volcanic planet – over One Thousand volcanoes!! Over 1600 large shield volcanoes!!
Io is the most volcanic body in the solar system Can be completely resurfaces in 1 million years!! Doesn’t have craters Io – moon of Jupiter
Can you think of some famous volcanoes?
Group Exercise Each group is given an information packet about a famous planet Your goal is to fill the “Volcano Profile” sheet In the end, each group will tell the class about their volcano
Volcanoes around the world
Next week Learn to identify the rocks in your backyard!
Homework: Bring in a rock Any rock you like It can be from anywhere –Your backyard –A trip you went on –Someone gave it to you
Andesite vs. Basalt Andesite - –from stratocone volcanoes (explosive) –more silica –more viscous (resists flow) –pinkish or reddish in color Basalt - –from shield volcanoes (not explosive) –less silica –less viscous –blackish in color