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Chemistry of Volcanoes

By Maya and Mikayla

¡BOOM!

Mt. St. Helen- Washington

On March 16, 1980, the first sign of activity at Mount St. Helens occurred as a series of small earthquakes. On March 27, after hundreds of earthquakes, the volcano erupted for the first time in 100 years. Steam explosions blasted a 200- to 250-ft wide crater through the volcano and covered the mountain with dark ash.

What makes volcanoes erupt?

  • Volcanoes erupt because of density and pressure.
  • The lower density of the magma compared to the surrounding rocks causes it to rise.
  • As the magma rises, bubbles start to form from the gas dissolved in the magma.
  • The gas bubbles exert tremendous pressure which helps to bring the magma to the surface and forces it in the air.

What is Lava?

  • Lava and Magma are not the same thing. Magma is underground, and lava is magma that has reached the surface
  • Magma is primarily a liquid made of oxygen, silicon, aluminum, iron, magnesium, calcium, sodium, potassium, titanium, and manganese.
  • Lava is red hot when it pours or blasts out of a vent but soon changes to dark red, gray, black, or some other color as it cools and solidifies.
  • Very hot, gas-rich lava containing abundant iron and magnesium is fluid and flows like hot tar, whereas cooler, gas-poor lava high in silicon, sodium, and potassium flows sluggishly, like thick honey in some cases or in others like pasty, blocky masses.
  • Lava is extremely hot. Lava can reach temperatures of about 1,250° Celsius.
  • Iron and Magnesium make a very strong bond and then get together with other elements, like iron, magnesium, potassium, calcium. They make crystals of minerals like olivine, which are beautiful yellow-green crystals that people call peridot.

Magma vs. Lava

Works Cited

Andrei, Mihai. "The Three Main Types of Volcanoes."

ZMEScience. N.p., 13 Jan. 2015. Web. 18 May 2016.

"How Do Volcanoes Form?" Learning Corner. N.p., n.d.

Web. 18 May 2016.

"Interesting Facts about Volcanoes." Fun Volcano Facts for

Kids. Science Kidz, n.d. Web. 18 May 2016.

NEWS9LIVE. “(Video) Mount St. Helens eruption blows off

1,000 feet from the top of the mountain.” Online Video Clip. Youtube. Youtube, May 7, 2016. Web. 18 May 2016.

"Volcano World." Why Are There Volcanoes? Why Do They

Erupt? Oregon State, n.d. Web. 18 May 2016.

Williams, Stanley. "What Is Lava?" Scholastic Teachers.

Scholastic, 4 Oct. 2013. Web. 18 May 2016.

"1980 Cataclysmic Eruption." Science for a Changing

World. USGS, n.d. Web. 18 May 2016.

Where do volcanoes form?

  • Volcanoes are usually located where tectonic plates meet. This is especially true for the Pacific Ring of Fire, an area around the Pacific Ocean where over 75% of the volcanoes on Earth are found.
  • While most volcanoes form near tectonic boundaries, they can also form in areas that contain abnormally hot rock inside the Earth. Known as mantle plumes, these hotspots are found at a number of locations around the globe with the most notable being in Hawaii.
  • While we certainly have some big volcanoes here on Earth, the biggest known volcano in our solar system is actually on Mars. Its name is Olympus Mons and it measures a whooping 600km (373 miles) wide and 21km (13 miles) high.
  • There are also volcanoes found on the ocean floor and even under icecaps, such as those found in Iceland.

How are volcanoes formed?

  • Most volcanoes are formed by the movement of tectonic plates on the surface of the earth.
  • These plates are basically huge pieces of rock that ‘float’ on the mantle (a layer of the earth that is sort-of liquid rock).
  • The tectonic plates are in constant motion, albeit very slow motion.
  • When a tectonic plate sinks, it sinks down into the mantle and becomes very hot, melting the rock.
  • This molten rock will gradually make its way up to the surface of the earth through a series of cracks.
  • As layer upon layer of lava builds up, a volcano is formed.
  • A stratovolcano (or composite volcano) is a conical volcano consisting of layers of solid lava flows mixed with layers of other rock.
  • A cinder cone volcano does not have any horizontal layers, and is instead a steep conical hill of tephra (volcanic debris) that accumulates around and downwind from the vent.
  • A shield volcano is a type of volcano built entirely or mostly from fluid lava vents. They are named like this because when viewed from above, you can see just how massive and imposing they are – like a warrior’s shield.

There are many factors that determine what kind of lava flow will occur and what type of volcano it will be. The amount of gas trapped in the lava, the kinds of minerals making up the lava, and how much pressure can be trapped in the area all affect the eruption and formation of the volcano.

What are volcanoes?

  • The U.S. Geological Survey defines a volcano as a vent in Earth's surface, either on land or on the seafloor, from which molten rock called magma, as well as ash and gases, can erupt or ooze.
  • Most people think of volcanoes as large cone shaped mountains but that is just one type, others feature wide plateaus, fissure vents, cracks were lava emerges, and bulging dome shapes.
  • Volcanoes can be active, dormant, or extinct

Fun Fact: The word volcano originally comes from the name of the Roman god of fire, Vulcan.

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