Volcanoes 4/27/16 Key Question: What are the different types of volcanic eruptions? Initial Thoughts:

Evidence 1: What is a volcano? Who can describe one? A volcano is a place where material from the inside of the Earth is escaping to the surface. The prime material involved is magma (or melted rock) that comes from the layer of the Earth known as the mantle.

There are three major types of volcanoes… Shield volcanoes Cinder cones Stratovolcanoes And one more for fun… Supervolcanoes

Shield Volcano Demo Why do you think the shield volcano is larger and flatter than other volcanoes? A shield volcano is formed almost entirely from great amounts of liquid/watery lava. This is called low viscosity lava. The lava flows out of a vent and slides down the side of the volcano, making a wide, gentle-sloping cone.

Shield Volcano – Mauna Loa Mauna Loa, in Hawaii, is a shield volcano, and the largest volcano in the world! (32,000 feet when measured from the ocean floor). Notice it’s low, broad shape.

Shield Volcano - Galapagos Islands (think Darwin)

Cinder Cone Volcano How do you think this volcano developed? What type of eruptions created this volcano? Make a prediction.

Stratovolcano (Composite) How do you think this volcano developed? What type of eruptions created this volcano? Make a prediction.

Evidence 2 Student Project Students will be researching and developing a model to demonstrate how the Cinder Cone and Stratovolcanoes (Composite) are created. Have students begin their research on the different types of volcanic eruptions. They can do a modified lab write for each of the eruptions.

Evidence 2 Student Presentation Students will be researching and developing a model to demonstrate how the Cinder Cone and Stratovolcanoes are created. Students can present their presentations. They need to explain their research about the different types of eruptions and demonstration their eruptions.

Evidence 3 – Note Taking Shield volcanoes Shield volcanoes can be a product of hot spots or oceanic vs. oceanic subduction They are frequently islands

Shield Volcano rocks.. Are generally low in silica, which is the major combination of elements in the Earth Silica is made of silicon and oxygen Instead of having a lot of silica, shield volcanoes have more dense elements, such as iron and magnesium This is why oceanic crust subducts (slides under the continental plate)… it is more dense than continental crust

Rocks associated with shield volcanoes… Basalt Gabbro

Hawaii, the perfect shield volcano Created by a hotspot Non-stop current eruptions since 1980! Types of Lava: Bombs, lapilli, fountains, Pele’s tears, pahoehoe, a’a Hawaii, the perfect shield volcano

Cinder Cones Relatively small in size, hundreds to 2,000 feet tall Usually steep sided and cone shaped. Found on the outskirts of all types of stratovolcanoes and shield volcanoes

Cinder Cone Eruptions Relatively small Lava – called scoria - is thrown into the air, and cools before it falls back down around the vent, building the volcano relatively quickly. Scoria is like crumbly “cinders”  Often glowing, and beautiful.

Cinder Cone Volcano – Wizard’s Island, Crater Lake

Lava Butte, Oregon

Composite Volcanoes aka Strato-Volcanoes Typically large, steep sided, up to 8,000 ft above their bases. Have a crater at the summit which contains a central vent or a clustered group of vents.

Composite volcanoes Found near “subduction zones.” Denser oceanic plates sliding beneath continental plates Oceanic crust melts, rises through continental crust, creates chain of volcanoes

Composite Volcano Eruptions Very violent, explosive and BIG!!! Entire sides of mountain gone in a few seconds.

Composite Volcano eruptions… Alternating eruptions of: Ash (lots of it) Tephra (rock) Pyroclastic flows (a dense, destructive mass of very hot ash, lava fragments, and gases ejected explosively) Lahars (mudflows) Lava, although not far reaching

More about composite cones Average life span of a million years Most famous eruptions in human history Ash can change global climate, temporarily Many Cascades erupt towards the north instead of straight up. Why? Northern sides of the volcanoes receive more sun, sun melts the ice and snow, water mixes with gasses causing acid, eats away at the rock, making it less stable

Historically cool… Mt. Vesuvius

A whole dead city, entombed in ash!

Stratovolcanoes and rocks… Andesite Diorite

Mt. Rainier (my favorite)

Mt. St. Helens Before eruption After eruption in 1980

Now onto supervolcanoes Hold on to your hats, it’s the end of the world!

What are super volcanoes? Super volcanoes are those that have extremely high levels of silica This makes for crazy viscous (thick & “sticky”) lava, and HUGE eruptions The lava is so viscous it doesn’t even allow for a cone shaped volcano

Types of rock Rhyolite Granite

So where can you find one…?

Yellowstone

Yellowstone Created by a hot spot Evidence from the Snake River Valley of past eruptions and calderas So explosive it clears away enough crust that low viscosity basalt can sometimes come up Can change the course of geologic history

Track it’s path…

For now, it creates neat stuff. Old Faithful Geyser Hot springs

When it goes… 60 feet of ash! At ONCE!

What are the consequences of it blowing? We could hear it blow in Washington Ash goes into the layer of atmosphere called the stratosphere, which will remain and block sunlight The entire Earth would cool, potentially causing an ice age If no ice age, definitely crops would die and food shortages would occur People are gonna die!

Locales Yellowstone Toba: Sumatra, Indonesia Long Valley Caldera, CA Others (about a dozen around the earth)

So why haven’t we heard about this before? They’re infrequent!

Analysis Explain what type of volcano would be the safest to live by and why. What could be the possible effects of a stratovolcano erupting near a city or town? What would you do to prepare for an eruption?

Summary What did you think about volcanoes and volcanic eruptions before this lesson? What did you learn about volcanoes and volcanic eruptions from this lesson? (Minimum of 4 sentences!!!) What are some further thoughts or questions you have about volcanoes and volcanic eruptions?

Reflection Explain what you would need in an emergency kit, if you lived close to a volcano.

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