Some Basic Cartographic questions...

[ladiestorm]

As I get deeper and deeper into the 'logistics' of making maps... I've come up with some general questions that I'm hoping someone can answer. These aren't about any particular software questions, more like atmospheric/geological questions, that will help me make better maps... so here it goes!

What is the difference between a marsh and a swamp? What atmospheric/geologic conditions would create one vs the other? Would it be feasible to come out of say a mountain range or forest and find oneself in either a marsh or a swamp? Are they more prevalent in northern regions or southern regions? Why do they form?

[Josiah VE]

"The world’s wetlands are ecosystems in themselves, and are defined by the flora and fauna they support. Marshes are nutrient-rich wetlands that support a variety of reeds and grasses, while swamps are defined by their ability to support woody plants and trees. Bogs are characterized by their poor soil and high peat content, while fens have less peat and more plant life than a bog." (http://knowledgenuts.com/2013/12/02/...bog-and-a-fen/) Just looked that up for you, but I sort of knew that, I just forgot.

I have very little knowledge about the atmospheric/geological side of maps, I just use a bit of common sense and have fun making them, not worrying too much about technicalities so I can't really answer your other questions.

[ladiestorm]

well, you've definitely given me something to think about! Perhaps we can get some other 'experts' to weigh in...

[Azélor]

The most helpful I've been able to find is this one : https://prezi.com/eiijdvxdvceh/the-d...bog-and-a-fen/

Their location seems to be mainly defined by geographic factors. There are also mangrove, another biome.

[waldronate]

An excellent web search term for this sort of thing is "physical geography". If you include an "introduction to" at the start of that term, then you will find the supporting web sites of quite a few physical geography textbooks.

As Josiah VE pointed out, the definition of marshes vs. swamps hinges on the presence of woody plants (trees). Marshes have lots of water and some condition that prevents trees from growing (salt, perpetual water, or so on) very large. One common marshland that we encounter in the US is the tail end of lake succession following glacial recession. The glaciers scraped out basins all over and those basins are filling with sediment now that the glaciers are gone. The lake starts out with a ring of marshy terrain around the shoreline and that ring draws in over time as sediment accumulates until the basin becomes a marsh and then prairie or forest.
The trees found in a swamp are typically endemic to the type of swamp and have features that allow them to survive the frequent to continual flooding. Mangroves have stilt roots, cypress trees have their knees to act as snorkels, and so on).

Interestingly, one of the biggest marshlands on the planet is seasonal. The tundra areas around the Arctic ocean thaw for the top foot or so, giving a huge marshland dotted with lakes and rivers. Marshlands tend to have excellent soil when drained due to their high organic content, which is why they are often in danger. Another large seasonal marshland here in the US was the southern Central Valley of California. The Kern and other rivers that emptied into the southern valley dropped all manner of goodies during their flood stage in the spring and summer. These goodies (minerals and other materials) triggered a massive surge of plant growth. At higher flood times, these waters would flow northward and fill out historic Tulare Lake. Flood management projects from the 1850s through the 1960s have turned that former marshland into a carefully managed sea of agricultural land and the seasonal lakes have pretty much all disappeared.

Pre-European husbandry also played a significant role in the balance of marsh vs swamp. The Yosemite valley, for example, is currently crowded with tall pine forests. The first Europeans, on the other hand, found a flat valley floor of grasses. The inhabitants would regularly set the valley floor afire to burn out the trees that were trying to form their climax community. This action pushed the valley floor to a grassy shrubland preferred by deer, a favorite prey animal.

Anyhow, I seem to be rambling now.

[ladiestorm]

No! This is a great discussion so far! But this also sounds like swamps and marshes tend to be more inland. It also sounds like they tend to be in flat land basins, like the Louisiana Bayou. Could a Marsh or swamp form in an area of land near or.close.to.the ocean? You mentioned the woddy element for swamps.,. Is it conceivable that a swamp developed within a few miles from the coast?

[waldronate]

https://nelson.wisc.edu/sage/data-an...tlands_nam.jpg shows a map of north American wetlands. Note that many of them are coastal.

A common type of wetland is the estuary, where a river runs into the sea. These estuaries typically contain tidal marshes, grasslands that deal with the ebb and flow of the tides daily.

If the land is sufficiently flat, the river will meander back and forth, forming delta after delta as it flows into the sea (see the Atchafalaya/Mississippi lowlands that comprise a large part of Louisiana). The flooded and semi-flooded backwater areas just over the natural levees that are the banks of the rivers contain forests (typically bald cypress) that are what a lot of us have in our minds as "swamps". Marshlands can be quite large, like the Everglades in Florida (which occupies pretty much the whole southern end of the peninsula).

http://plan.risingsea.net/ERL/S16_No...olina_Full.jpg shows some of the coastal wetlands in a state like North Carolina.

[ladiestorm]

I knew about the wetlands of NC, since that's where I live I don't know why I didn't think of that. I guess I should explain my question. I'm currently working on a map where I have a large swamp area on the southwestern peninsula, that covers just about the whole peninsula. I also have a marsh that has formed in a basin at the foot of a mountain range. I just wanted to make sure both were geologically feasible before I continued on with the rest of the map...

I also have a friend that wants me to make a map for one of his games... and one of his specifications for this island he wants me to map, is that the whole southern half of this long island is swampland, right up to the coast...I was trying to decide if I needed to break it up before it reached the ocean... because he also wants this map to be 'as realistic as possible'.

[waldronate]

I picked North Carolina as an example because I thought that you might be able to relate to it.

The critical parts of marshes and swamps are relatively flat areas with lots of water, including open water areas. Marshes are such lands that don't support tree life for one reason or another. Swamps have tree life.

Wikipedia has some fairly nice discussion on swamps and marshes, including distribution:
https://en.wikipedia.org/wiki/Swamp https://en.wikipedia.org/wiki/Marsh

Coastal swamps tend to shade into coastal marshes, depending on the local conditions. In the case of a mangrove swamp, the "trees" march right into the ocean. One thing to watch out for is that you want the swamp areas to be accumulating sediment (even if very slowly), not losing it. If the area is subject to strong storms or other erosion factors that cause churn in the coastal area, trees won't have time to grow very tall and the coastline will more likely be marshland (likely shading into swamp past a rind of marsh). The size of the island and its latitude will also be a factor due to the type of plant life available.

One of the fun parts about wetlands is that you can put one just about anywhere that's flat and wet and it's plausible. You might get to dance a little about the exact form of plant life (e.g. a polar wetland isn't going to have mangrove or cypress swamps and an equatorial wetland is unlikely to have an assortment of pines and spruces), but it's not too hard. If the client wants giant trees marching into the ocean, you can always invent a salt-tolerant species. Or have a creepy dead-forest area that was caused by relatively recent (within a few hundred years) subsidence of the coastal area, perhaps due to earthquake. http://www.nwnature.net/earthscope/copalis.htm is an example of this sort of thing.

[ladiestorm]

well, this is a fantasy based game he's running... and the swamp he's asking me to make is home to several 'water elf' communities. So it shouldn't be too hard. And the swamp in my map is in a plane that's home to the gods... so I guess I can get away with a lot, there . But thank you so much for the help!