"Geology happens," one of my college professors used to say. Wall Arch, located in Arches National Park along the Devils Garden Trail, collapsed sometime during the night of August 4, 2008. Now that's geology in action.

The arch, according to the Arches National Park Web site, was first reported and named by Lewis T. McKinney in 1948. For the geologists among us, it was a free standing arch in the Slickrock member of the Entrada sandstone. Before it fell, the opening beneath its span was 71 feet wide and 33 1/2 feet high.

Using ArcGIS Explorer we went to have a closer look, beginning by using Find Place to locate Arches National Park.

Below you can see that got us to Arches, but we still didn't know where Wall Arch was located.

To find the location of the fallen arch we went to the Explorer Resource Center (File > Resource Center)  and clicked the Layers tab to add the US Topo Maps layer (by clicking on its thumbnail). 

Once the topo layer was added we could zoom in and look for the Devils Garden area that the news item on the Arches National Park Web site mentioned. That proved easy to find, and as we zoomed in to view the 1:24K scale topo maps we found that the arch was clearly marked.

We could tilt our view to see how the arch formed along one side of a sandstone rib, typical of many of the park's 2,000 or so arches. Another interesting perspective could be gained by using the swipe tool to examine the imagery underneath the topo layer.

To complete our little geology exercise we used Create Notes to place a point at the location, changed the note title, and added the URL of the news item to the popup note text.

Here's the result (no pun intended).

We saved the result with an adjusted view property and the popup window open, so that when you click here to open it you will automatically zoom to the (former) location of Wall Arch and see the popup display the news item from the park's Web site. We could also have e-mailed the result directly from Explorer. Geology in action, Explorer in action!