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Pacific Northwest Geologic Mapping and Urban Hazards

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Geologic maps and databases of the North Cascades
30' x 60' (1:100,000 scale) quadrangles

North Cascade map index Mt Baker Suak River Skykomish River Snoqualmie Pass Robinson Mtn Twisp Chelan Wenatchee Click on index map for geologic map, availability, reference lists, and other information about quadrangle.

In 1975, the North Cascades geologic mapping project was born of a need to understand the geologic setting of significant crustal earthquakes in the North Cascade region. The project evolved to produce geologic maps of 8 1:100,000 scale quadrangles covering most of the North Cascades and the Methow River region on the east (See Figure).

Most of the project field work is done. Maps and reports are available and some are still in preparation.

Map unit color Miocene flood basalts
Map unit color Tertiary extensional basin deposits and volcanic rocks of the Cascade Volcanic arc
Map unit color Regionally metamorphosed rocks of the North Cascades crystalline core
Map unit color Unmetamorphosed Mesozoic and Paleozoic marine rocks
Map unit color Thrust plates of the Northwest Cascades System, the Helena-Haystack melange, the Eastern and Western melange belts and the Ingalls terrane
Map unit color Mostly metamorphic and igneous rocks of the Quesnellia Terrane

For a history of the North Cascades project, click here.

Link to The Geology of the North Cascades: a Mountain Mosaic, a non-technical explanation of North Cascade geology.

Link to a historical publication: Routes and Rocks: Hiker's guide to the North Cascades from Glacier Peak to Lake Chelan.

Availability of ROCK SAMPLES from the North Cascades Project

This site is maintained by the Pacific Northwest Urban Corridor Geologic Mapping Project, part of the Geology, Minerals, Energy and Geophysics Science Center

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