In Which We Have One Last Adventure

January 21, 2017

I am starting to get ready to go back East. My next host family will be in New Jersey, which is by the other ocean.  I will have been coast to coast in Four months! My host family wanted to go on one last adventure before I leave, so here's what we saw:

This is what's left of Mount St. Helens.  This is as close as we can get in the wintertime because it's really snowy up there.  
Up until 1980 it was just another mountain in the Cascade Range, like Mount Rainier. But on May 18, 1980, the lid blew off.  Literally.  My host mom explained it with this drawing:

The Cascade glaciers are COMPOSITE volcanoes. It means that one time they erupt they pour out lava that hardens into rock.   The next time, all that comes out is ash, so there's a layer of ash. Then another layer of rock, and another of ash and so forth. One special feature of Cascade volcanoes is the glaciers on the top of each one.  That's the key to understanding the Mt. St. Helens eruption.

The glacier works like the cap on a soda bottle.  If you shake the bottle, pressure builds up under the cap. Take off the cap and the soda sprays out.  Volcanoes work just like that. See the pinkish color in the middle of the drawing? That's the magma chamber, where the lava comes up from underground (Fun Fact: magma is just a name we use for lava that hasn't come up to the surface yet).  Pressure builds up in the magma chamber before an eruption, just like the soda bottle.  But the magma is HOT.  The heat from the magma melts the glacier on top, which makes the ice thinner and weakens the cap. 

The water from the melting glacier rushes down inside the cone of a composite volcano and turns all the ash layers to slush.  Then when the cap gives way and the top explodes, all the slush rushes out and the rock layers collapse onto each other. Basically, when Mt. St. Helens erupted, the whole side of the mountain slid away, and covered the valley with ash slush mixed with water, dirt, rock and debris. This is called "Lahar."

There are really cool lava tubes you can walk through in the summer, but in winter there's just too much snow.  I was actually kinda happy that we didn't get really close to it; volcanoes are not my favorite thing.  And Fern said at least it was warm in the car.  We came home sleepy from our last adventure; time to get to bed; I'll be travelling soon.