ECOS Guide to the Ecology of the Northern Rockies

		ECOS Guide to the Ecology of the Northern Rockies

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Geological History of Western Montana

Earth processes play an essential role in ecology. Ecosystems are dependent upon the structural foundation determined by the dynamic physical earth. A fundamental step in studying ecology is to understand the physical processes that shape landscapes.

Western Montana provides an excellent setting to witness and experience a wide variety of earth processes and their ecological implications. These processes range from the effect of plate tectonics on mountain habitats to the effect of river processes on fish migration. The Bitterroot, Sapphire, and Mission mountains, and the Clark Fork, Bitterroot, and Blackfoot rivers, are in close proximity to Missoula. This proximity provides the opportunity to easily observe and experience connections between physical processes and local ecosystems. Additionally, western Montana contains one of the richest geologic histories of any area in the country. From 3.3 billion year old rocks exposed in the Beartooth Plateau to 12,000 year old Glacial Lake Missoula sediments deposited in the Missoula Valley, the rocks in Montana record a vast array of numerous tectonic environments, climate changes, and even a meteorite impact!

Follow the links below to learn more about Montana's Geological History

Montana's Geological Highlights
Montana's Geology by Time Period

Montana's Geological Highlights

Name	Period of time	Years before present
Glacial Lake Missoula	Quaternary	~12,000
Yellowstone volcanism	Latest Tertiary, and Quaternary	2.1, 1.3, and 0.63 million
Tropical Montana	Late Tertiary	~20 million
Coal production	Early Tertiary	~60 million
Lewis Thrust Fault	Late Cretaceous – Early Tertiary	~72 million – 58 million
Idaho Batholith	Cretaceous	~73 million
Belt Supergroup	Precambrian	~1.5 billion – 800 million

Montana's Geology by Time Period

Geologic Time Period	Description	Years before present
Cenozoic Era	Climate change and volcanic activity	65 million years ago – Present
Mesozoic Era	The age of dinosaurs and the formation of Montana's mountains.	248 – 65 million
Paleozoic Era	The formation of the "Pangea" supercontinent.	543 – 248 million
Proterozoic Eon	Sediments from a sea are deposited creating the Belt formations.	2.5 billion – 543 million
Archean Eon	The begining of Montana's history and the formaton of the continetal crust	3.8 - 2.5 billion

The ECOS program is sponsored by the University of Montana's Division of Biological Sciences, and the College of Forestry and Conservation. Carol Brewer Program Director, Division of Biological Sciences. Paul Alaback Program Co-Director, College of Forestry and Conservation.

ECOS is supported by the GK-12 Program of the National Science Foundation.
Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the National Science Foundation.