Wetumpka, Alabama and the Wetumpka crater


Wetumpka, Alabama is a city of 6,528 (according to the 2010 Census) about 50 miles southeast of Alabama's geographic center. Wetumpka sits just south of Alabama's fall line, which divides the hard rock of the Appalachian foothills to the north from the soft sedimentary rock of the coastal plain. Wetumpka is itself divided by the Coosa River: residential Wetumpka is northwest of the river, downtown Wetumpka southeast. Immediately southeast of downtown Wetumpka the topography rises 200 feet steeply. Hill Street, just east of the Wetumpka courthouse (Wetumpka is county seat) is aptly named.

This hill is actually the rim of Alabama's only known impact crater. The Wetumpka impact crater is of Cretaceous age and is about 5 miles in diameter. This map shows the outline of the crater. The southwestern rim is heavily degraded, apparently by a torrential backwash of displaced water right after impact. I would go into more detail about the impact crater, but there are already several websites that do a much better job than I ever could. Here's the website of David King, professor of geology at Auburn University and leading expert on the Wetumpka crater. Here's a neat account of a field trip to the crater led by David King. Some of the older materials say that the Wetumpka crater hasn't been radiometrically dated, which is no longer true: here's a 2011 LPSC abstract giving a (U-Th)/He age for the crater of 84.4 +/- 1.4 million years.

So why did I make a Wetumpka page, anyway? I visited Wetumpka in March 2011. I didn't get to see any exposures of crater rock: I wasn't able to spend much time looking, and apparently the good ones are on private property, anyway. (For anyone interested in seeing the crater, there are yearly tours in early March: email wetumpkaevents at bellsouth dot net for details.) However, I did get to see some neat paintings of the Wetumpka impact done by artist Jerry Armstrong that I had heard about at the LPSC Wetumpka radiometric dating talk. My friend Olivia Curry took pictures of these paintings, which I've reproduced below. Click on any of the headings for a high-resolution version. (I heard Jerry Armstrong's paintings will soon be hung in a new Wetumpka crater visitor center along US 231. Please email me at william dot m dot vaughan at gmail dot com if you have any news about the visitor center or the paintings.)

The shallow Cretaceous sea pre-impact (impactor in background)

A raptor and an ammonite oblivious to the Wetumpka impact

Same picture as above showing the ammonite more clearly

A dead raptor and the post-impact tsunami and firestorm

The crater starting to flood (note central peak)

Pterodactyls over the flooding crater

They should update the crater age on this poster

Wetumpka geography and topography, again

The Civic Center (and the mayor of Wetumpka)

The Bibb Graves Bridge connecting NW/SE Wetumpka

Wetumpka's courthouse serving Elmore county

A restaurant in front of the crater rim

Finally, I want to offer a very sincere thank you to everyone in Wetumpka (particularly the mayor, the woman at the courthouse, and the woman at the Civic Center) who generously arranged to show me Jerry Armstrong's paintings. I hope to return soon for a longer look at the crater. Thanks also to Olivia Curry for taking these photos.


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Will Vaughan. Last revision April 8, 2011.