How the Earth was Made

Mt. St. Helens in Google Earth

One of my favorite TV shows, being the nerd/geek/geology-phile that I am, is The History Channel's How the Earth was Made. It takes the long view of history, going in depth on subjects like plate tectonics, erosion, and climate. Forces the Earth has been generating and enduring for four and a half billion years. The original show looked into the life history of the planet, from star dust to life ark. The series that sprung from that (currently with two seasons) has episodes that focus on famous natural features, from the Grand Canyon to Mount Everest to Loch Ness.

I have done a fair amount of reading on how the Columbia Basin was formed. Glaciation, mega-floods, clashing continents, and basalt flows are just some of the creative/destructive powers that it took to make such a unique place on earth. There's enough geologic upheaval in this area to fuel a new episode of the show, should it continue into a third-season. But there was an episode about a feature within the basin. It stands tall on the horizon, easily viewable from Portland. While Mt. Hood gets most of the attention, it's Mt. St. Helens that makes all the noise.

I've taken several trips up to see this massive mountain that so famously blew her top. Just a little over a year after my birth, the side of the mountain bulged and then erupted out, sideways. Scouring the surrounding hills, flattening forests, and flooding the land it caused incredible devastation. Yet the mountain gave warnings that something big was about to happen. This invited scientists in for a short period of study, much of what was learned saved lives in other parts of the world and makes for interesting television.

The ancient Romans believed the volcanic activity of Italy was the result of the forges of Vulcan, the smith of the gods. The Hawaiians thought that their island chain had been created by hot-headed Pele. It's taken hundreds of years of study, but we now know much about how volcanoes form and function.

We are probably all familiar with how the crust of our Earth is made of titanic plates. These clods of dirt, though formed of many types of rock, are largely composed of granite. This particular stone floats on top of the heavier materials that make up the Earth's fiery mantle.But the act of a solid floating on a liquid is not one of levitation, rather it is one of displacement. The chunks of the Earth's crust are heavy and gravity would like them to sink. Like getting into a bath tub and watching the water level rise, all of that hot lava below is also trying to rise, squeezed into every nook and cranny of our imperfectly formed planet.

The crust is full of holes that have have been filled with magma. The weight of the crust pushing down is met with the resistance of the mantle already there, which creates enough pressure to build mountains. These mountains, volcanoes, are like a microcosm of the plates, they float on a lake of lava. The weight of the mountain is causing it to try to sink into this lake, but the liquid in the lake has no where to go but up. These forces find a balance and the mountain sleeps. But if one weakness is found, the lava will exploit it and make an explosive get away.

Approaching Mt. St. Helens in September, 2007

While these forces may remain in balance for years, decades, even centuries, Mt. St. Helens is a very active volcano due to a fatal, balance shattering trait. The May, 1980 eruption taught some interesting lessons, most importantly that the mountain was rotten to the core. Mountains are funny things, they seem invincible and immobile. They modify the weather around them, creating snow and rain. While much of the snow melt and rain waters run off the mountain side and eventually join the Columbia, the rest of it soaks into the ground. And like rain water seeping into your home's foundations and wreaking havoc, the same is more true of volcanoes. The problems lie in the minerals that make up a volcano. Famously, sulfur is a smelly component of volcanic activity. As precipitation percolates into the heart of the mountain, it heats up, picks up sulfur and heads back to the surface. This literally undermines the roots of the mountain, causing internal erosion that compromises the integrity of the structure. As the stones rot they can no longer hold back the incredible powers of the magma below. Eventually something's got to give, and when it does you'd better be prepared to get out of the way.

So long as hot lava lies below and rain falls from above, volcanoes like Mt. St. Helens are likely to blow off their decayed tops and play devastation with the surrounding landscape and river basin from time to time. While the land around us may seem strong, like the mountain, we must remember that the Earth is constantly in motion, just like a river. It moves slowly most of the time, but occasionally it make great, destructive leaps.

Additional images from my 2007 trip to Mt. St. Helens.

Happy hunting,
Brett