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The Future That Awaits Idaho

by Bill Bonnichsen and Marty Godchaux (Bios)

In 1788, one of the world's first geologists, Scotsman James Hutton, proposed the Principal of Uniformity, or uniformitarianism, which was expressed in 1830 by another early geologist, Englishman Charles Lyell, as the well-known phrase: "The present is the key to the past." To peer into Idaho's geologic future we can rearrange this thinking into: "Our geologic past predicts our geologic future," or "What has gone around might come around again."

Things that might happen in the next few thousand to hundreds of thousands of years

1. Climate Change: In the near-term Idaho may get hotter and stormier as greenhouse gases accumulate in the atmosphere, leading to more erosion when rivers flood. But, it is likely that within the next hundred thousand years — as has occurred several times in the last couple of million years — continental glaciation may return, covering the northern half of North America and high mountain ranges in ice. This would include a colder and wetter climate, with increased erosion and perhaps even the return of such features as Lake Missoula and periodic massive floods if ice dams are breached.

Balanced Rock, located south of Buhl in the Salmon Falls Creek Canyon [Credit: Bill Bonnichsen]

2. Volcanism: Certainly there will be more basaltic lava eruptions in the Snake River Plain region. If some occur in areas where the ground-water table is shallow or in streams, they could be quite explosive and form tuff cones hundreds of feet high or even maars (volcanic explosion craters) as much as a mile across.

3. Land subsidence in the eastern Snake River Plain region: The area around Idaho Falls, Rexburg, and Ashton will continue to sink slowly as it has for the last million years or so, as the Earth's upper crust cools following the passage of the Yellowstone Hotspot topographic bulge. The surface in that region would likely get as low as around Burley and Twin Falls, farther west. Such subsidence might lead to the formation of lakes and meandering about of rivers and streams.

Bliss landslide [Credit: Bill Bonnichsen]

4. Strong earthquakes, valley subsidence, and mountain-range uplift: As the Basin and Range Province continues to become wider because of crustal stretching we can expect these things to occur. Such activity will be especially prevalent in easternmost Idaho where the current seismic activity is concentrated, and perhaps even farther east as the province continues to get wider.

Things that might happen in the next few million to tens of millions of years

1. The Yellowstone Hotspot may move eastward and bring about more gigantic explosive eruptions of rhyolitic magma and the collapse of more huge calderas.

Geyser deposit, Soda Springs [Credit: Bill Bonnichsen]

2. Erosion will continue so that in central and northern Idaho the canyons get wider and deeper and the mountains gradually wear away; and in southern Idaho the volcanic plateau will be replaced by valleys and hills as the canyons become wider and wider and eventually merge with one another.

3. The widening of the Basin and Range Province might become so pronounced that the Gulf of California extends northward as far as Idaho, letting the ocean flood part of the state.

4. The Baja California peninsula and slices from the west side of California may drift northward along the San Andreas fault or future strike-slip earthquake faults, adding to Oregon and Washington and changing Idaho's climate and drainages, and perhaps even causing compressive deformation of the Earth's crust, leading to the development of new mountain ranges and volcanism as far east as Idaho.

Pole Creek Top vent area, in the canyon of Pole Creek on the west side of the Owyhee Mtns [Credit: Bill Bonnichsen]

Things that might happen hundreds of millions of years in the future

1. The Pacific Ocean basin is closed up as North America crashes into Asia and all the outlying Island arcs, such as Japan. This would be accompanied by great amounts of crustal deformation, the raising of new mountain belts, and the probable volcanism and formation of new batholiths in Idaho. If this process is carried to the extreme, Idaho might be thrust beneath eastern Asia, just like the Indian subcontinent is now being shoved beneath southern Asia where the Himalayas have risen. If that happened, Idaho would fold up and be converted to metamorphic rocks. Parts of it would melt, coalesce into magma blobs and rise up to erupt as volcanic rocks and make even more batholiths.

2. Eventually, when North America reverses its westward drift, it may again move eastward as the Atlantic Ocean basin closed again (for the 3rd or 4th time). This would lead to renewed mountain building in the eastern U.S. This event likely would be accompanied by breaking apart of North America along internal weakness zones, such as the Basin and Range Province. This could break Idaho into two separate parts located on two new continents.

Things to expect to happen way, way, way in the future — billions of years out

1. First, Idaho gets deep frozen: As the planet loses its internal heat, and perhaps as the sun radiates less heat or the Earth migrates even farther from the sun, the Earth's surface will cool so much that the oceans freeze solid and glaciers cover most continental areas. This would be a return to "Snowball Earth," similar to what happened about a billion years ago.

Oreana church, made from tuff and sediment blocks quarried nearby [Credit: Bill Bonnichsen]

2. Then, Idaho gets fried to a crisp: After the sun gets old and burns up all of its hydrogen, it will turn into a red-giant star, swallowing the Earth and the other inner planets. If Idaho lasts that long, this last cataclysm will surely get our magnificent state. After all, we're just a little piece of a great big Solar System, and the even much bigger Milky Way Galaxy.

So, lets all enjoy Idaho while we're here. The state is bound to keep changing!