Atlantic Coastal Plain

bobpbx

Piney
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Oct 25, 2002
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Pines; Bamber area
I'm always interested in the bigger elevation changes found in our relatively flat pine barren land, especially ones that are steep. Most of them dip into a cedar swamp. There is one on the Factory Branch headwaters that I have always been impressed by. You can see them on the topo as bunched up elevation lines. Each line is, I think, 10 feet. Last weekend I stumbled onto one in Brookville that was also impressive, and I'll be going back to explore it a bit more.

Boyd, a recent post of yours showed elevation lines that are in smaller increments. Can you post a snippet from your topo for this area below?

 

Hewey

Piney
Mar 10, 2005
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Pinewald, NJ
Looks like an interesting area. I like the area on the south side of the Webbs Mill Branch. One area is very steep when you come up out of the cedars. The elevation change from the cedars to the top of the 136' hill out there is a fairly quick.

Chris
 

Spung-Man

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Jan 5, 2009
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Richland, NJ
loki.stockton.edu
Relict Cold, Nonglacial Landscapes

I'm always interested in the bigger elevation changes found in our relatively flat pine barren land, especially ones that are steep. Most of them dip into a cedar swamp.
Bob,

You make a keen observation. There is an asymmetry to many Pinelands stream valleys, and a solution to the question can be found if you carefully think about Ice Age conditions. So what bank orientations seem steepest, and what geomorphic forces affected one bank more than another to create this asymmetry?

Spung-Man
 

bobpbx

Piney
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Oct 25, 2002
11,235
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Pines; Bamber area
Bob,

You make a keen observation. There is an asymmetry to many Pinelands stream valleys, and a solution to the question can be found if you carefully think about Ice Age conditions. So what bank orientations seem steepest, and what geomorphic forces affected one bank more than another to create this asymmetry?

Spung-Man
Hmmm, I do remember reading someone's thesis that had some clues :))), but being having a dense head for details, I've forgotten at the moment. I think it has to do with the winds coming off the glacier piling sand on the southern side or something to do with the way the sun melted that bank first, or even the way the river current flowed. It seems there is another post relative to this topic??.....strong katabatic winds piling up hairpin parabolic dunes?
 

Boyd

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Ben's Branch, Stephen Creek
Here you go. I used a 5 foot contour interval to show more details in the pines. Unfortunately, this is not one of the areas that the USGS has covered with the high resolution 1/9 arc second LIDAR DEM data, so the source is 1/3 arc second data.






Here is what the source DEM looks like, in both 2d and 3d views





 

Spung-Man

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Jan 5, 2009
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Yes! It is believed that this valley asymmetry is related in part to sunshine or “insolation” dynamics. The Pine Barrens experienced extended cold periods for the last couple of million years. During frigid episodes the ground remained frozen late into the summer (deep seasonal frost) or remained frozen all year round (permafrost). Although air temperatures were quite cold, the sun’s rays were still warming. Radiant energy was strong enough to thaw the ground in direct exposure to the sun, especially when snow cover was thin.

North- and East-facing slopes are often steeper here because they received the least amount of thawing sun. South- and West-facing slopes received the most amount of radiant energy, so they thawed and wasted away much more quickly than North- and East-facing slopes. This effect is not very well pronounced in the Arctic since there the sun’s angle is very low and not very intense. That is not the case in the Pine Barrens. It is believed that in frozen mid-latitude South Jersey the resultant slope asymmetry is well expressed because of insolation (Demitroff, 2007: 82–83; French et al., 2007: 54).

Nice LiDAR-images, Boyd. That is a great viewing tool.

Spung-Man
Demitroff, M., 2007: Pine Barrens Wetlands: Geographical Reflections of South Jersey’s Periglacial Legacy. MS thesis, University of Delaware, Newark, DE, 244 pp.

French, H.M., Demitroff, M., Forman, S.L., and Newell, W.L., 2007: A Chronology of Late-Pleistocene permafrost events in southern New Jersey, eastern USA. Permafrost and Periglacial Processes. 18: 49-59.
 

bobpbx

Piney
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Oct 25, 2002
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Pines; Bamber area
Thanks Mark....I had it backwards in my head, that cleared it up.

Thanks Boyd....that 55 foot drop in elevation to the cedar swamp is impressive. At the red shade it is all big upland oak trees, and then zoom!....in a cedar swamp all the vegetation is different.
 

Boyd

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Ben's Branch, Stephen Creek
Nice LiDAR-images, Boyd. That is a great viewing tool.
Actually the images in this thread are not LIDAR, they are the 1/3 arc second DEM that the USGS has for the whole US. LIDAR is only available in selected areas, and it is far more detailed. I posted a bunch of examples here: http://forums.njpinebarrens.com/general-discussion/8149-lidar-pines-very-cool.html

I'm not sure, but I've read that the 1/3 arc second DEM was created from the USGS 24k topo's, by overlaying a grid and entering the elevation at each point. If so, then it does provide a different way of looking at the data in 3d, but probably not many new insights. The LIDAR imagery is very high resolution and you can actually see things like cellar holes.

Thanks for the quick primer on insolation dynamics Mark - really fascinating stuff.