This month at our Lifelong Learner Lunch we talked about volcanoes. We covered how they formed, the differences between various kinds of volcanoes, some famous eruptions, and how scientists predict eruption. This is a fun topic, as it helps us to understand more of the processes of plate tectonics as well as the landscapes we live in. Without volcanoes, we wouldn’t have beautiful things like gemstones or the fascinating block formations of the rocks at Gooseberry Falls.
Volcanoes are places around the world where hot, molten rock spills out of fissures in the Earth’s crust. The molten rock then cools upon contact with the (relatively) cold air or water and forms new land. When molten rock is inside the world’s crust, we call it magma. We call it lava once it has erupted. While volcanoes are creating new land, other geologic features are melting and recycling other, older stretches of land. You can find a wonderful diagram here from Britannica that visualizes the process very nicely.
Some kinds of volcanoes, like Mt. St. Helens, are known for their loud, explosive, and destructive eruptions. These volcanoes are called Stratovolcanoes and tend to occur along the edges of plate boundaries close to the ocean. Stratovolcanoes are tall and tend to be found along the edges of continents. Other volcanoes, like Mt. Kilauea, are known for their flowing lava rivers and fountains, fascinating lava lakes, and nonexplosive eruptions. These tend to be Shield Volcanoes, which are known for having low-viscosity lava. Shield volcanoes are long and low volcanoes that form from repeated deposition of low-viscosity lava. The higher the silica content that magma has, the more explosive the eruptions tend to be. Stratovolcanoes have high silica content due to the melted continental crust that feeds their magma chambers.
Most of the eruptions that happen on Earth actually happen underwater, along the mid-ocean ridges. These volcanic mountain ranges consist of divergent plate boundaries where the tectonic plates are literally pulling apart from each other. As this happens, lava surges up into the opening, where it comes into contact with ocean water and cools dramatically. The black smokers (hydrothermal vents, pictured on right below) associated with these volcanoes are places where volcanic gasses are released. The gasses precipitate quickly upon contact with cool water, which is why it looks black. These gas plumes also release heat into the surrounding waters, creating fascinating ecosystems not found anywhere else in the world.
If you are interested in lunch and a 90-minute program on various topics, I encourage you to sign up for our Lifelong Learner Lunches! Our upcoming programs are as follows:
Sat. Oct. 12 – Minnesota Bison Conservation Herd with Minneopa State Park Speaker
Thurs. Nov. 21 – Intro to Backyard Birding
Sat. Dec. 14 – Christmas Bird Count
The Bison program will be presented by a guest speaker from Minneopa State Park. Ney staff will be presenting both the Intro to Backyard Bird Watching and the Christmas Bird Count programs. As always, please register ahead of time for these programs so that we can make sure that we have enough food and beverages for everyone. You can register online or call the office to sign up.
I hope that you have a great day!
-Liz Sheppard
Ney Nature Center Naturalist