What’s a volcano?
How does it get its shape?
A volcano is a mountain with a hole that extends deep into the Earth. They’re an exciting way to learn about the 3 layers of the Earth: the crust, mantle, and core.
The crust is the solid outer layer of the Earth that we live on.
The mantle below the crust is made of mostly solid rocks and gases.
The core is the very hot ball-shaped center of the Earth made of mostly metals. The inner layer of the Earth’s core is solid, but the outer layer of the core is liquid.
The Earth is very hot beneath the crust, and this is how magma is formed. Magma is hot molten (or liquid) rock and gas found in pockets of the mantle. Magma (or lava once it’s reached the Earth’s surface) is what erupts from volcanoes. It’s very hot and glows red. It turns darker when it cools.
Sometimes lava flows like an explosion, and other times it is very slow.
Here are a few examples of lava flow:
How many volcanoes are there?
There are about 600 known volcanoes in written human history, but scientists also say that we don’t actually know exactly how many there are. There are volcanoes that have been inactive for a very long time, and scientists aren’t always sure if they will erupt again. There are also likely countless others hidden beneath the ocean.
Scientists believe that at any given moment, there are 20 volcanoes around the world erupting. That means 20 could be erupting RIGHT NOW!
How do volcanoes get their shape?
The way a volcano erupts will determine its shape.
Shield volcanoes are formed when lava erupts from a vent that begins as a crack in the Earth’s crust. The lava from these volcanoes is more fluid and travels farther than other kinds of volcanoes. The volcano is formed over time from many thin layers of lava that have cooled and hardened. The islands of Hawaii are made from the largest chain of shield volcanoes in the world.
Did you know that there are shield volcanoes on Mars and Venus, too?
A caldera is a bowl-shaped hole that happens when a volcano collapses once it’s emptied out all of its magma. Some are formed in one event, and some form slowly over time. Some calderas were caused thousands of years ago by volcanic eruptions bigger than any recorded in human history.
Lava domes erupt very thick lava. Because it’s so thick, it doesn’t get very far before it cools off and hardens. This means that the lava piles up near the vent making a dome shape. These often form in calderas in larger volcanoes.
Cinder cones are made when melted rock fragments spray into the air and cool quickly as the fall back to the ground. The land around the opening of the volcano in a pile and form a cone shape. These tend to be smaller and may be found on or around larger volcanoes.
Composite conses (aka stratovolcanoes) are known for their explosive eruptions. Their lava cools and hardens before it gets very far making their classic cone shape. They also get very large and steep. They are made of layers of ash, rock, dust, and lava. On the inside, stratovolcanoes are made of a system of underground conduits, kind of like pipes. This means that they can erupt from their tops and their sides. Some might also have smaller volcanoes nearby.
You can make your own volcano at home!
With a few household materials, you can make a mini volcano at home.
Of course these aren’t real volcanoes, but they’re still exciting!
Construction paper, tape, and scissors (to make the cone for the volcano)
Dish Soap (optional)
Food coloring (optional)
A container for your volcano to erupt in (we did ours in the bathtub)
We used the construction paper to create the cone for our volcanoes. We just curled them into a cone shape, taped them, and trimmed them to fit the bottles.
Once we got a good fit on our cones, we took the bottles out to prepare our lava mixture.
I put a few tablespoons of baking soda into each bottle and filled the bottles about half-way with water. We added a little dish soap to give them some extra bubbles. You could do this without the dish soap as it’s not necessary for the chemical reaction between the baking soda and vinegar.
If you want colored lava, you could also add food coloring to this mix.
Now it was eruption time!
We poured the vinegar into another empty bottle to make it easier for Pie to pour into the volcanoes, and we carried our volcano materials to the bathtub to keep clean up easy.
Pie got into the tub and poured the vinegar into our volcanoes.
What a surprise when the volcanoes erupted and sent bubbles flowing down the sides of their cones.
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