The Arizona Geological Survey have created a rather nice virtual field trip and very useful virtual field trip about the Marcus landslide in Arizona. It is available here:

http://www.azgs.az.gov/MarcusLandslide_2008.shtml

The slide is a 500,000 year old rock slide that has has a length of about 2 km from scarp crown to deposit toe (see Google Earth image below) and a deposit volume of about 5.25 million cubic metres. The elevation difference is about 500 m.

Two minor criticisms from me, though:

1. The site does not give the lat/long of its location, which makes looking at it on Google Earth rather more difficult than it ought to be. The location of the crown is: 33°40’47.27″N, 111°48’1.31″W. The deposit extends almost due east from this point;
2. The site states that “Poised for collapse, a heavy rain, a bolt of lightning, or an earthquake could have spontaneously triggered”. It is highly unlikely that lightning would trigger failure.

Finally, there is a paper in Geomorphology describing the landslide in more detail, including its dynamics, failure and age. It is available for downloading as a pdf here. There reference is:

Douglass, J., Dorn, R.I. and Gootee, B.F., 2004. A large landslide on the urban fringe of metropolitan Phoenix, Arizona. Geomorphology, 65, 321-336. doi:10.1016/j.geomorph.2004.09.022