Volcanoes and You

1. What is a volcano? A volcano is a mountain that forms when layers of lava and volcanic ash erupt and build up around a vent.

Active v. Dormant Volcanoes Most of Earth’s volcanoes are dormant, meaning not active. There are over 600 active volcanoes currently on Earth. Active means erupted in the last 1,000 years.

Where is the nearest volcano to Tucson located?

Is it A-Mountain? A-Mountain is composed of igneous extrusive rocks, but is not itself a volcano

What about Picacho Peak? Picacho Peak, which you pass when going to Phoenix, is made up of igneous rocks. Like A- Mountain, it looks like a volcano, but it is not one.

Nearest local volcano to us... Sunset crater, near Flagstaff, which last erupted in 1065.

2. Features of a volcano Magma – melted rock/molten material below Earth’s surface. Vent – Opening in Earth’s surface where magma can flow out. Lava – Magma that has flowed out of the Earth’s surface. Crater – Opening at the top of a volcano Ash and Gas – Explode out of the crater.

Magma Features of a volcano

3. Where do volcanoes occur? Volcanoes can occur at 3 places 1.Divergent boundaries – an area where Earth’s tectonic plates are moving away from each other. Diagram: Example: volcanos in Iceland

Divergent volcanoes in Iceland

Where do volcanoes occur? Volcanoes can occur at 3 places 2.Convergent boundaries – an area where Earth’s tectonic plates collide into each other. Volcanoes form when one plate subducts, or slides under the other plate. Diagram: Example: Andes Mountains in South America, Cascade Mountains in NW USA

Convergent volcanoes

Mt. St. Helens...before and after 1980 erruption

Where do volcanoes occur? Volcanoes can occur at 3 places 3.Hot spots – parts of Earth’s mantle that are hotter than surrounding material, forming melted rock which rises to the surface as magma. Diagram: Example: Hawaiian Islands

Hawaiian volcanoes m/ m/ for live web cam of Pu’u O’o crater

Hot spot is making the Hawaiian Islands

4. 2 types of volcanic eruptions Magma that contains trapped gases causes eruptions to be explosive. Think of shaking a can of soda and then opening it. Explosive eruptions have a lot of silica in the magma, for example melted granitic rocks. Mt. St. Helens is a good example of an explosive volcano. Magma with little silica is effusive and flows quietly from the volcano. Quiet eruptions have basaltic magma. Good examples of quiet eruptions are Hawaii and Iceland.

5. 3 types of volcanoes, based on material and eruption style Shield volcanoes - are broad, gently sloping volcanoes built from fluid basaltic lavas.

3 types of volcanoes Composite volcanoes - composed of both lava flows and pyroclastic material. They tend to have steep sides, and can have explosive eruptions.

3 types of volcanoes Cinder cone- forms when material is ejected high into the air and falls back to Earth as a pile around the vent. Usually small, with lots of water and gas in the magma.

Compare sizes of volcanoes

What would Earth be like without volcanoes? Write down 2 ways Earth would be different on your notes sheet.

Mt. Saint Helens eruption - 8:27 am

8:32 am

8:33 am

New lava dome in Mt. St. Helens

Fuego Volcano in Guatemala

Colima volcano in Mexico

Mt. Wrangell in Alaska

Mauna Kea and Mauna Loa

Mount Pinatubo in the Philippines

Mt. Fuji in Japan

Mt. Krakatoa, Sumatra

volcano

Add these notes to our Table of Contents!

Photo and image credits s/images/010103_nps_volcanoe19.jpg&imgrefurl= olcanoes/&h=200&w=250&sz=9&hl=en&start=2&tbnid=p3IWTtsd- waSJM:&tbnh=89&tbnw=111&prev=/images%3Fq%3Dvolcanoes%26svnum%3D10%26hl%3Den %26lr%3D%26sa%3DG url= =ZokkTQZIuvP9fM:&tbnh=72&tbnw=122&prev=/images%3Fq%3Dsunset%2Bcrater%2Barizona% 26svnum%3D10%26hl%3Den%26lr%3D%26sa%3DN &wcsuffix=3100http:// &wcsuffix= /jpg/_ _volc_bbc_203.jpg&imgrefurl= h/ stm&h=300&w=203&sz=16&hl=en&start=6&tbnid=XE3EeVJzq71i- M:&tbnh=116&tbnw=78&prev=/images%3Fq%3DIceland%2Bvolcano%26svnum%3D 10%26hl%3Den%26lr%3D%26sa%3DG

Photo and image credits s/images/010103_nps_volcanoe19.jpg&imgrefurl= olcanoes/&h=200&w=250&sz=9&hl=en&start=2&tbnid=p3IWTtsd- waSJM:&tbnh=89&tbnw=111&prev=/images%3Fq%3Dvolcanoes%26svnum%3D10%26hl%3Den %26lr%3D%26sa%3DG url= =ZokkTQZIuvP9fM:&tbnh=72&tbnw=122&prev=/images%3Fq%3Dsunset%2Bcrater%2Barizona% 26svnum%3D10%26hl%3Den%26lr%3D%26sa%3DN &wcsuffix=3100http:// &wcsuffix= /jpg/_ _volc_bbc_203.jpg&imgrefurl= h/ stm&h=300&w=203&sz=16&hl=en&start=6&tbnid=XE3EeVJzq71i- M:&tbnh=116&tbnw=78&prev=/images%3Fq%3DIceland%2Bvolcano%26svnum%3D 10%26hl%3Den%26lr%3D%26sa%3DG

Photo and image credits url= JrqB3jM:&tbnh=142&tbnw=143&prev=/images%3Fq%3DIceland%2Bvolcano%26svnum%3D10%26hl%3Den%26l r%3D%26sa%3DG 99SHU MtShuksan,PictureLake.jpg&imgrefurl= a2usa.html&h=441&w=325&sz=81&hl=en&start=1&tbnid=4xfwvuNj QgexzM:&tbnh=127&tbnw=94&prev=/images%3Fq%3Dcascades% 2Bmountains%26svnum%3D10%26hl%3Den%26lr%3D%26sa%3D G eology/mclean/Dinosaur_Volcano_Extinction/media/hotspotL.gif&im grefurl= _Extinction/pages/hot_spot.html&h=365&w=508&sz=13&hl=en&star t=1&tbnid=6RT0yxvUco93hM:&tbnh=94&tbnw=131&prev=/images% 3Fq%3D%2B%2522hotspot%2522%2Bvolcano%26svnum%3D10% 26hl%3Den%26lr%3D%26sa%3DG