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Virtual Field Trip to the Marcus Landslide

McDowell Mountain Regional Park, AZ

North-looking photograph of the eastern side of the McDowell Mountains , where  the Marcus landslide runs from left to right.  The landslide might not look like much right now, but it will be easier for you to discern the landslide after taking this virtual field trip. 

Introduction:


The McDowell Mountains in northeastern Phoenix host one of the largest known landslides in Arizona. The entire landslide is within the McDowell Mountain Regional Park preserve  (Figure 1) .  Discovery of this large feature took place during the construction of a learner-centered education course funded by the Arizona Board of Regents. 

The landslide deposit is named in honor of former ASU Professor of Geography Melvin Marcus.  A world-renowed physical geographer and student favorite, Professor Marcus passed away in 1997 while leading a class field trip in the Rocky Mountains. 

 

Figure 1. The Marcus landslide deposit at different scales. 
   A) A satellite image placing Phoenix in geographic context with the Marcus landslide deposit (courtesy of Earth Sciences and Image Analysis Laboratory, NASA Johnson Space Center). 
   B) A remotely sensed image of the McDowell Mountains viewed from the east with respect to the Marcus landslide deposit (courtesy William Bowen; Click here for a higher resolution perspective. Click here for another oblique view of the slide.)
    C)  Location of the Marcus landslide deposit with respect to growth in Scottsdale, Arizona.Note how the development is starting to grow out next to very steep slopes on the eastern side of the McDowell Mountains, even though the landslide deposit rests in a land preserve.
 

 
Landslides and their deposits litter steep unstable hillslopes across Arizona.  The Grand Canyon in northern Arizona  hosts thousands of landslides, with innumerable failure prone slopes and cliffs (Figure 2).  In fact, the Surprise Canyon landslide in western Grand Canyon remains the largest discovered landslide in the state. 
 

Figure 2.  A Landsat image of the Grand Canyon, courtesy of NASA, merged with the topography.  The rock fall image, caught by Niccole Cerveny, illustrates what happens when very steep slopes are continuously undercut by river erosion.

 

The McDowell Mountains have one important thing in common with Grand Canyon,  steep hillslopes.  The Marcus landslide failed along plane with a very steep angle of 33 degrees, seen by clicking here.  The presence of the Marcus landslide cautions against unwise development next to steep slopes of Phoenix mountain ranges. 
 

The Marcus Landslide is technically called a rock avalanche.  The Marcus landslide is among the biggest rock avalanches called sturztroms with a volume over 7 million cubic meters.  The slide mass extends about one kilometer from the mountain front with a width of 0.5 kilometers.  The source exhibits classic features of large landslides of breakaway scar and fall zone (Figure 3).
 

Figure 3.  A west-looking view of the Marcus landslide deposit from a height of 200m, constructed from a 10m resolution digital elevation model in MicroDEM. There is no vertical exaggeration. Ripples in the foreground represent DEM artifacts.

 

This virtual field provides a tour of the Marus landslide deposit (click here for aerial photograph) is intended for anyone interested in desert geomorphology (geomorphology is the science of how Earth's landscape is sculpted). This virtual field trip is more than just a set of pretty pictures, although you can certainly just look at the photos.  We explore reasons for landslide, the probable age of the landslide deposit,  and classic features of large landslides deposits that you can see on the Marcus rock avalanche. 

But like any other geography field trip, we include more than just the focus.  You will also see the flora, fauna, and cultural landscape features normally explored (e.g. Figure 4) on a real field trip. 

 

Figure 4.  Gila monster hiding in a little alcove.  The material making up the alcove consists of cemented landslide debris on the east end of the landslide deposit.

 
How this virtual field trip works:
 

The field trip structure involves a series of stops with panoramic images of the surrounding terrain. 

Each stop has one panoramic image.  From that panoramic view, clickable hotspots take you to particular locations of interest. 

Be sure to look at the reference image located at the base of each stop.  The reference image provides a viewshed of the panorama; this viewshed helps you maintain your position with respect to the landslide deposit.  The yellow pie slice represents the viewshed; you stand virtually at the pointy end and look our towards the rounded edge (Figure 5). 

After exploring all the hotspots for a particular stop, we suggest you move on to the next panoramic stop and repeat the same procedure. 

 

Figure 5.  The upper image is an example of the reference map used to guide you on this virtual field trip.

The funny pie shaped feature with a number is the viewshed you will see at, in this example, stop 4.  At this location, you are virtually standing in the pointed part of the orange viewshed and looking out towards the rounded edge.  In this example, the photograph is what you would see from site 4, looking up at the bottom of the slide.  The combination of aerial view and ground view helps you know where you and helps you navigate the field trip.  The upper image (reference map) was generated using MicroDEM.

 
 

 
To start the virtual field trip, please click the link below: Marcus Landslide Virtual Field Trip