Places I've been

Visiting Mount St. Helens

 

Ed and I went to Mount St. Helens National Volcanic Monument near Toutle, Washington. Mount St. Helens is an active volcano that had a powerful eruption just 30 years ago. The eruption left a huge horseshoe crater where the peak used to be. The land around it changed a lot too. All the trees were knocked down, and lakes were filled in. The ash from the volcano and mud covered everything. When we were there we saw that plants were starting to grow again. Someday it might look like there was never even an eruption.

Volcanoes are mountains, but unlike other types of mountains because of how they are made. Far below the earth’s crust is an area so hot that rocks melt into a thick, flowing matter called magma. Magma rises out of a crack in the crust called a vent and lava builds up the volcano around it over thousands of years to create a stratovolcano like Mount. St. Helens. Magma is called lava when it is on the surface of the earth.
Most volcanoes on land form near subduction zones. Subduction zones are where two of earth’s plates run into each other and one is forced under the other. The earth’s crust outer shell is made of many slabs called tectonic plates. These all float above the hot, soft mantle layer where magma is. The Pacific Ocean is over the plate that is forced under the plate that North America is on. This is why the west coast has earthquakes and volcanoes.

Mount St. Helens before the eruption

Eruptions happen when magma builds up deep down in the volcano builds up then explodes out. Magma is lighter than the rock around it so it rises to the surface from the mantel. While it is rising the pressure changes and the magma bursts out. It is kind of like when corn kernels are cooking and then it pops open.

Don’t worry though. Most volcanoes are not active, but are either extinct or have been dormant (sleeping) for thousands of years. Scientists have special machines that can tell when they are starting to wake up and they let everyone know.