October 29, 2012 in Features

Earth’s natural changes aren’t always gradual

E. Kirsten Peters
 

Many subscribers to this newspaper live on top of a pile of ancient lava flows. The pile is nothing to sneeze at – it’s thousands of feet thick. Part of that depth is shown in places like the Snake River Canyon, where you can see lava flows stacked on top of one another through hundreds of vertical feet. In almost all places, each lava flow in the pile is a flat layer, very close to horizontal. And all the layers are made of the same sort of rock – one that is created when high-temperature lava belches forth from the earth and cools to form what we geologists call basalt (rhymes with ‘ma’ and ‘salt’).

There was a time that we geologists believed Earth processes were pretty gradual, taking place over millennia or epochs. We had some good reasons for thinking that. By chance, a couple of the first Earth processes we studied closely were glaciers and the erosion they cause over time and streams and the way they shape the planet. Guess what? Both sets of processes are, indeed, mostly gradual ones.

But then geologists of the late 1800s made a bit of a mistake. As they looked at examples of gradual processes, and also at the great age of Earth as well, they jumped to a conclusion. The profession started to put a great deal of emphasis on the notion that all natural change on Earth is gradual.

Actually, of course, the matter is far more complex. There are, indeed, a number of gradual processes on Earth. But some change is quick: meteorite impact is one clear example. And, as recent research based on ancient glacial ice cores has shown us, a lot of natural climate change has a fast tempo, taking place in just one human generation.

The lava flows on which we live are another example of what can result from a quick geologic process. Each lava layer was created when the earth vomited forth a prodigious amount of red-hot, iron-rich lava, similar to what we see on a much smaller scale today on the Big Island of Hawaii.

Sometimes it’s easy to slide into the notion that natural processes are somehow “nice,” what you might call warm and fuzzy. After all, Mother Nature nurtures us, does she not? But major volcanic eruptions that covered areas measured in the hundreds of miles across were nothing short of disastrous. All sorts of living creatures, those that walked or crawled on the earth or swam in lakes and rivers were wiped out by the flows of high-temperature lava during the time we geologists call the Miocene. (This ancient time predates Homo sapiens, so on the bright side no Native Americans were killed by the lava flows.)

Sometimes natural processes are gradual, and sometimes Mother Nature seems loving and benign. But we fool ourselves if we forget that abrupt and destructive natural processes are also woven into the very fabric of our world.

E. Kirsten Peters, a native of the rural Northwest, was trained as a geologist at Princeton and Harvard. This column is a service of the College of Agricultural, Human and Natural Resource Sciences at Washington State University.


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