Karst Topography Near Houston

[TheNiche]

I was looking at the Bellaire quadrangle of the 1915 topographic maps of the Houston area and noticed something that had escaped my attention previously. In the area south of Pierce Junction and running westward for about eight miles, there is a band of Karst topography, replete with numerous sinkholes and lakes. It's not as pronounced as somewhere like central Florida, but its certainly unusual.

It also brought to mind the sinkhole that had opened up underneath Almeda Road. I did a little poking around on the internet and found this article, which cites the presence of a very fine silt in a soil layer at as little as eight feet below-ground in that area, which is in the band of Karst topography that I'm referring to.

I'm just curious, are there any geologists or geophysicists on here that have specific knowledge of this area. In particular, are there any risks to building structures in such areas? What would be required to mitigate the risks, if anything?

[innerlooper]

Karst is usually associated with carbonate rocks, which are pretty scarce around here.

[TheNiche]

Yeah, I know. That's what makes it so odd.

[Croberts]

I have long thought the same thing...the inward facing tick marks on the circular contours means a depression. But there is no limestone for a long way down, so karst is not the proper term. There is a long history of subsidence in the Westbury area, it was clear when I lived there in the 1960s that the streets did not drain properly because they had sunken in places, and many walls and fouindations were cracked. But the only thing I ever saw that could pass for limestone was in buffalo bayou in Memorial park, right at the water level. 

 

The term sinkhole is commonly and mistakenly used to describe areas that were scoured by liquid from pipline or sewer failures. That is the explanation for the almeda road sinkhole described in your article. 

 

For sinkholes to develop, there has to be a limestone region in which large solution cavities exist. This is typically caused by uplifting a limestone block, Central Florida, the highest part of Florida is an example. Another is in Burnet, Longhorn cavern sits on an uplifted block of limestone, a horst, and millions of years of water draining through the uplifted block caused the cavern to develope. There is no limestone to speak of on the Gulf Coastal Plain around Houston, the nearest would be the Oakville escarpment near Lagrange.

[Croberts]

Now that I think about it more, I am convinced that these depressions are associated with subsidence. There are two sources for subsidence. The pierce junction feature also marks the location of oil fields, they were drilling there in the 1960s, I do not know when they started. I remember a gas flair on the road that was the southern extension of hillcroft (blue ridge?) below south main.

 

There is a small linear feature north of willow water hole right over my neighborhood and street (5807 Arboles) and the effects of subsidence were visible there by the late 1960s, about 10 years after development. At the time this map was drawn, it was probably rice fields or pasture. This map is before drainage and scraping of Braes bayou and Willow water hole.

[Croberts]

I just realized that the contour interval is 1 foot. Most of the depressions are then 1 foot, some, with two contours are two feet deep. I remember walking in these areas when they were pastures and the only sign that there were depressions was that the flat prairie would turn into marsh, then back into prairie.I also remember that my dad would order two dumptruck loads of sand to spread in our yard because of the subsidence every 2 years from 1958 to at least 1971.

[Croberts]

It also seems that the pierce junction feature is often on the highest the elevations decrease as you move away from the feature.

[Original Timmy Chan's]

Looks like "prairie pothole" wetlands to me.  Take a look at an old aerial of Houston...you'll see these little prairie potholes all over the place.

 

Or...look at a current aerial of the Katy Prairie.  Lots of little depressions all over.

 

I don't see any "Karst" reference on the map, but maybe I'm just not familiar with the symbology.  That said, isn't the area you're talking about full of salt domes?  Maybe the 1915 cartographers mistakenly referred to salt domes/salt caverns as Karst? 

[Ross]

It also seems that the pierce junction feature is often on the highest the elevations decrease as you move away from the feature.

 

Pierce Junction is the surface expression of a salt dome, as is Blue Ridge over on McHard Road. The best nearby example of how a salt dome can create high spots is High Island, closely followed by Barber's Hill.

 

If you look at the 1944 images on Google Earth, you can see prairie potholes all over the place, as well as just how few trees there were back then.

[Croberts]

Thanks Ross and Original Timmy Chan!  I suppose that the oil fields in the area are related to the salt dome. This is the first time I have heard the term "prairie potholes". The word Karst was not on any map. Niche had commented that these features on the 1915 map looks like what karst typically looks like on topo maps in general. Students in classes that study topo maps are shown similar features and told that this is karst. Typically though the contour interval is 5 to 20 feet depending on the map.

 

 I have long thought (since the 1980s) that this was an odd karst like feature on this map, knowing that this was not Karst, but I never did any research on this topic, this is one of the things I love about this forum. longstanding questions get answered! 

[Ross]

Here you go http://texaswetlands.org/wetland-types/prairie-pothole-and-marsh-wetlands/

[Croberts]

Thanks Ross, this was very informative. I new about prairie pimples, but the term prairie potholes was new.

[Croberts]

There is another version of this map, I am attaching it here. This one has hundreds of individual survey elevations measured down to tenths of an inch. These must be the survey points that were used to generate teh contours. It would be interesting to compare these points to survey points from recent times.

 

I use this in one of my GIS course exercises. here are the instructions for searching for and downloading maps from the USGS.

 

Search for "U.S. Topos" a USGS site. Read the first page, then choose Download Maps. This takes you to the U.S.G.S. store.  Now search for Bellaire, Texas. Notice the red marker. left click it, look at the list, and send maps you want to the shopping cart. Then go to the shopping cart, check the maps you want to download and click download.

 

These are GeoPDFs. The modern ones have multiple layers, including imagery, roads,hydrology, etc. You can open the pdf and turn layers on and off. They are also projected, so you can load them in GIS software as well as simply using them as PDF's.

 

Probably everything that was produced by the USGS (with the exception of the manuscript maps) are available through this site, so you will find multiple additions of the same years maps at times.