Geology permeates our daily lives to an extent few of us realize. The very shape of the landscape, the earth resources upon which our society depends, and the health and safety of our communities that may be at risk from geologic hazards are all part of the geologic fabric that surrounds us.
We've put together some resources about geology and geological issues that are intended for the non-geologist, from field guides to road signs. And keep coming back, as we'll keep adding resources as we find them.
Montana's Island Ranges
— by Lee Woodward
Sapphires in the Butte –Deer Lodge area, Montana—by Richard Berg
Field Guide to the Judith
Mountains, Central Montana
— by Lee Woodward and others
Butte Under the Hill: A Brief Introduction to Mining and Geology — by Sharon Lewis
Geologic Road Signs across Montana— sponsored by Montana Math Initiative
Magnificent Journey—A geologic river trip with Lewis and Clark through the Upper Missouri River Breaks National Monument
—by Otto Schumacher and Lee Woodward
Earthquakes: History and Seismic Safety in Montana
—by Mike Stickney and others
Montana in the Geologic Past— by Eugene S. Perry
Below is a brief discussion of the geologic timeline, as it relates to Montana
Geologic time, from the formation of the Earth at ~4.6 billion years ago to the present, is understood and represented by layered rocks throughout the world. By understanding the relative ages of layered and cross-cutting rocks, and the fossils they contain, geologists have developed a geologic time scale. Relative ages are cross-correlated with numerical ages derived from radioactive isotopes of elements contained in some of the geologic units. Using fossils and radiometric ages, geologists can compare the geologic strata of Montana with the "type section" of Devonian rocks exposed in the Devon area of southern England.
For example, using fossils, geologists can compare certain geologic strata in Montana with the "type section" of Devonian age rocks in Devon, England and determine that their ages are the same. Radiometric dates tell us that Devonian rocks fall in a range of 369–410 million years ago.