Jun 08, 2008 - 08:15:50 CDT
Southwestern North Dakota is not exactly an old country for no men, to play loose with a recent movie title.It is an old country, though, some of it laid down as long as 72 million years ago.
When a guy out in Rhame, say, calls something "old as dirt," he means more than he might know.
Its geological age explains why such elemental indelicacies as erionite, uranium, molybdenum and selenium are found beneath the ground out there.
They were spewed out by ancient Rocky Mountain volcanoes that brought up molten magma from the Earth's mantle around 25 million years ago. The mantle is the layer between the Earth's thin crust and its deep core.
It also explains in part why underground water in that region is not only old, but highly saline, and diminishing in supply.
Since Earth itself is 4.5 billion years old, geological age is relative to what happened after that.
What tips the age difference in North Dakota is the surface action of glaciers, vast sheets of grinding ice that moved south during ice ages.
The last ice age, some 13,000 years ago, didn't reach further into what's now southwestern North Dakota than the Missouri River Coteau region.
The receding glaciers left permeable gravel, potholes, richer topsoil and relatively shallow underground water stores, with a lot of interaction between the surface and the water.
Ed Murphy, state geologist, said there's no direct evidence that far southwestern North Dakota was ever messed with by a glacier. Geologists have yet to find erratic granite boulders out there that mark the paths of glaciers, he said.
So the old rocks and deposits still stand, subject purely to erosion. And that old country also is semi-arid in climate, so erosion is the slow work of ages.
It's why the Killdeer Mountains and buttes like Bullion and Sentinel are not rounded like the Turtle Mountains, Murphy said.
It's why river drainages like the Little Missouri River are not filled in.
It's why uranium, or erionite, our old volcanic visitors, still lay in neat geological strata instead of having been carried away on glacial melt water.
It's also one of the reasons why, unfortunately, the primary source of underground water out there is so very old.
Bob Shaver, who directs the Water Appropriation Division for the State Water Commission, said people need to better conserve water, which comes from the geologic Hell Creek and Fox Hills formations that formed 65 million to 80 million years ago.
The water is ancient, more than 1,000 feet deep and has been moving through these formations for thousands of years, Shaver said.
While fresh water recharge can penetrate the formation, the recharge zones are far off in Montana and South Dakota, and the whole area doesn't get much snow or rain to help.
Monitoring shows some wells in the Fox Hills aquifer are declining at the rate of 1 or 2 feet per year.
Shaver said ranchers should conserve water by "valving back" those wells so water doesn't run over the ground.
The Fox Hills water level is declining, while at the same time, demand for water is at an all-time high, for oil, coal and ethanol projects.
Shaver said the department steered the Richardton ethanol plant away from Fox Hills water because the impact on existing water users in that aquifer would have been unacceptable. "The use for the aquifer would have been huge," he said.
The department is particularly concerned about flowing artesian ranch wells that run unchecked; some are only a few feet away from losing natural flow.
"They're slowly, locally mining the aquifer and it's only a matter of time before the aquifer will cease to flow in low-lying areas," Shaver said.
And in an old country like southwestern North Dakota, no water would mean no men.
(Reach reporter Lauren Donovan at 888-303-5511 or lauren@;westriv.com.)
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