Tectonics, Geomorphology and Geologic Materials (The influence of the physical environment on watershed dynamics.) A Watershed Dynamics Tutorial © John F. Hermance February 9, 2003 (Images from Tasa Graphics among others) Contact information: Jack Hermance Environmental Geophysics/Hydrology Department of Geological Sciences Brown University, Providence, RI Tel:

Regional tectonics can play a controlling role in local watershed dynamics. (Images from Tasa Graphics cannot be used without permssion of the company.)

Plate tectonics drives current orogenic activity.

Orogenic activity is enhanced at plate boundaries.

How does the “rock cycle” determine local water decisions?

Understanding the evolution of geologic features, generically or on a site specific basis, can give insight into watershed processes, hence water-related decisions.

Igneous rocks

Understanding the evolution of geologic features, generically or on a site specific basis, can give insight into watershed processes, hence water-related decisions. Metamorphic rocks

Understanding the evolution of geologic features, generically or on a site specific basis, can give insight into watershed processes, hence water-related decisions. Sedimentary rocks

The Northwest US.

The “Rock Cycle” Exposed. The Northwest US.

Igneous rocks

Batholiths

Intrusive igneous rocks

Extrusive igneous rocks

Metamorphic rocks

Sedimentary rocks

The Northwest US.

The Western US. An Archetype Example

The Western US. Physiographic Landforms

The Western US. Basin & Range

The Western US. Colorado Plateau

The Western US. Snake River Plain

The Western US. Cascades

The Western US. Sierra Nevada

The Western US. Southern Rockies

The Western US. Northern Rockies

The Western US. Rio Grande Rift

The Western US. California Central Valley

The Western US. Southern Basin & Range

The Future (and the past).

The Oldest Bedrock: Shield Areas of the World.

“Basement”; then...

“Basement”; now...

Where or what is “basement”?

Evolution of the crust

Grand Canyon Exposure as a Microcosm of the North American Crust (From California to Massachusetts.)

Next. we’ll look at the shallow unconsolidated section.

We are interested in glacial features...

... streambed features...

... and fluvial deposits.

Sedimentary sorting.

(Back to metamorphism: Sediments are ephemeral.)

(Metamorphic Grade.)

A digression on glaciers.

The Ice Age

Maximum extent of glaciation.

“Fossil” glacial features.

(Moraines.)

Glacial landforms.

Glacial rebound.

Present day mountain glaciers (or not) as “keys to the past”.

Glacier in cross-section.

Stresses in a glacier crossing a rock step.

A tour of Canadian glacial forms.

The Athabasca.

A dry valley.

A hanging glacier.

A hanging glacier up-close.

A trip up the Athabasca. (Note principal features.)

The Ice Falls.

The Ice Falls on approach.

The Ice Falls on target.

This is why we came here.

(Radio waves through ice?)

This is why we came here. (Radio waves through ice? What does this have to do with NASA, and the Lunar Lander (Apollo Program)?)

“Fossil” glacial landforms.

Stream morphology.

Meanders.

Meanders - Flooded.

Meanders - Flooded - and buried.

Stages of stream evolution.

Deltas

Drainage patterns driven by bedrock patterns.

Current “geologic” processes can modify “current” hydrology.

Mass movement can modify local hydrology & vice versa.

Affect of subsurface water on mass movement.

Evolution of bedrock.

The paradigm for subsurface hydrology. Organic layer Leached layer Weathered bedrock Bedrock

Physiography of North America.

Groundwater regions of the US. (Note concordance with geology.)

End of Presentation (Tectonics, Geomorphology and Geologic Materials) © John F. Hermance; February 9, 2003 Go to Soil & Water.