Idaho Geology Virtual Field Trip

A Virtual Field Trip

Welcome to the Magic Bus and our exciting virtual field trip. We will be traveling around Idaho and viewing examples of many of the geologic features we have studied in this class. Please submit your permission slip now and sign the bus log.

Here is your trip sheet for keeping track of your visits. This will prove that you have been there! Now look over the field trip check list to make sure you are prepared.

Here are our scheduled stops, but remember that you may magically skip, re-arrange, or re-visit sites in any order simply by selecting the destination of your choice. Here is the bus schedule. OK, put on your imaginations and load up for the trip of your life! Click on your desired destination arrow or click on the upper right hand corner of each card and just hold on for the whole trip. You may return to this location at any time by clicking on

Does Idaho have fault zones? Do we ever have earthquakes? How about some history? Can we exit the bus and take pictures of the Challis quake and near Borah Peak?

Hawaii is a chain of “hotspot” islands. Idaho has something similar, believe it or not! Come and visit the Snake River Plain in Idaho, with both intrusive and extrusive features on exhibit. And don’t forget to stop and tour the Craters of the Moon National Monument.

How about the Panhandle and volcanism? And what, exactly, is the Idaho Batholith? Can we get off the bus for more photos?

Idaho has experienced a lot of glacier action, too. But was it alpine or continental in form? Click on one or the other to go there and see.

Groundwater mark ~

The subject of Groundwater brings to mind aquifers. Do we have any major aquifers in our state? Click North or South to visit sites about some important aquifers.

What about mass wasting? I’m sure it happens all over Idaho and quite often, as well. There was an excellent example in 1998 Bonners Ferry that you may want to visit. This bus can not only move us around the state in a flash, it moves back and forth in time as well. Photo op!

Surface water mark

We may not be like Finland or Minnesota, but there are plenty of lakes and rivers in our state. Would you like to visit any rivers or lakes?

Mining mark

Geology has historically been important in the settlement of Idaho. One useful result of geology is the mining of valuable resources that make our everyday lives easier and more convenient. Let’s look at the history of mining in Idaho. And be sure to click on “Idaho Mining Images” at the end.

Sign the bus log to make the trip! Name

Date

Name

Date

Name

Date

Trip sheet - Respond to these questions as you travel and discover information • • • • • •

When and where was Idaho’s largest earthquake? Name 5 volcanic features found at Craters of the Moon Monument. Name the major example of continental glaciation in North Idaho. Identify the largest aquifer in the state. Explain the mass wasting event in 1998 Bonners Ferry. In which county do you find Lake Pend Oreille and the origin of the Payette River? • What geology-related event lead to the establishment of the Idaho Territory? And place the special marks found at each destination in the chart below. Quakes

Volcanism

glacier

Ground Mass-water wasting

Surfacewater

Mining

Virtual Field Trip Check List Have you handed in your permission slip? Have you picked up your trip sheet? Do you have warm clothing, including rain gear? Remember to dress in layers because we will feel the warmth of the bus and the chilly spring weather outdoors as we explore and take pictures. Do you have your lunch and an extra snack? Bring enough of your tasty snack to share with your teacher? Do you require any special things: Deep Woods Off, sunglasses, sun block, Benadryl for bee stings, etc. ? Do you have your camera, field notebook and a writing utensil for taking notes, responding to questions, and writing down what your pictures are meant to show? Do you have your I-Pod and cell phone? Turn around and take them back to your mom in the car………you won’t require them. Did you pack your imagination?

Faults Found in Idaho New data from the Clearwater complex, north-central Idaho, define the origin and history of the complex. The complex is divided into an external zone bound by normal faults and strike-slip faults of the Lewis and Clark Fault Zone (LCFZ) and the associated Noxon/Moyie Fault Line, and the smaller faults into adjacent Washington, Montana, and Canada.

Faults Found in North Idaho

Faults Found in North Idaho

Central and Southern Idaho have some rift zones (areas of faults) as well. The areas around Challis in Central Idaho and the Basin/Range and Middle Rockies regions have earthquake potential as well as formations based on parallel fault lines. So have we ever had a major earthquake in Idaho? Return to the bus, please. Earthquake mark 

The Snake River Plain is a broad arcuate topographic depression that extends across southern Idaho (figure 1 below) The western Snake River Plain sits in a fault-bounded graben while the eastern Snake River Plain (ESRP) is a large structural downwarp that formed due to the weight of the overlying volcanic rocks. The Owyhee Plateau is genetically related to the Snake River Plain, although it has remained a highland region. The map below shows the geography of the Snake River Plain and surrounding areas.

Current studies suggest that the Snake River Plain resulted from the passage of the North American Plate over a stationary mantle plume or “hotspot” that is currently located beneath Yellowstone National Park (Figure 2) or what is often referred to as the Yellowstone Caldera or Yellowstone Plateau. The North American plate migrates at a rate of approximately 4.5 mm/year over the "hotspot".

OK, kids, back on the bus!

Cameras away, return to the bus.

Volcanism mark

The Idaho Batholith is composed of Cretaceous granite and covers approximately 35,000 km2 in central Idaho; it is roughly 320 kilometers long by 120 kilometers wide, and 8 kilometers thick. The Atlanta Lobe and the Bitterroot Lobe of the Idaho Batholith are separated by metamorphic rocks in the Salmon River Arch. The Atlanta lobe is older, 100 to 75 Ma., while the Bitterroot lobe is mainly 85 to 65 Ma. There has been debate about the inclusion of the Kaniksu Batholith as part of the larger Idaho Batholith. Its geologic make-up makes it of similar origin, however. The Kaniksu Batholith or Lobe, which makes up the north/south trending Selkirk Mountains, located in the northern portion of the core complex, is a mixture of granite and granodiorite of the same type as the rest of the batholith and is of the same Cretaceous origin in age.

The granitic rocks of the Idaho Batholith formed during late Cretaceous compression event. At this time, the dense oceanic Farallon Plate was subducted beneath the more buoyant continental North American Plate. The oceanic crust was subducted into the lithosphere until heat, pressure, and slab dewatering initiated melting of the oceanic plate. This melting and the superheating of water that was also subducting formed basaltic magma chambers. These chambers rose up through the lithosphere because of differences in buoyancy. They then caused partial melting of overlying continental crust, to form a melt of granitic composition.

Return to the bus, it’s almost lunch time!

There are many examples of alpine glaciation in Idaho, especially in the high peaks of the Bitterroots that form the boundary and continental divide between Idaho and Montana, as well as higher regions of Central Idaho like Sun Valley and McCall.

Glaciation occurs at high latitude, as well as high altitude as seen in Idaho.

Continental glaciation is evident in the northern Panhandle. The Purcell Lobe of the Cordilleran Ice Sheet wandered down during the Ice Ages and retreated several times. This left behind some large glacially-scoured lakes (Pend Oreille and Priest) and a glacially dammed lake (Coeur d’Alene). It also resulted in the formation of the gigantic Glacial Lake Missoula, responsible for the Spokane Floods that reshaped parts of the Panhandle, as well as Eastern and Central Washington.

The following drawing and aerial photo explains how the Purcell Trench and Lake Pend Oreille may have been carved out from existing rock structure.

The trench stretches from Coeur d’Alene in the south, all the way into Canada. Now let’s head back to the bus.

Glacier mark