WETLANDS AND GEOLOGY
Wetlands are often dismissed as "wasteland" - thought of as breeding ground for mosquitoes and unpleasant odors . Wetlands, however, are very important natural resources . They provide shelter for animals and fish, as well as improve water quality and reduce flood and storm damage. In addition, wetlands provide unique recreational settings for activities such as bird watching, fishing, canoeing, and hiking.
There are four main types of wetlands: swamps, bogs, fens, marshes. The amount of water in a wetland area can vary from shallow to highly saturated areas. Likewise, wetlands can vary greatly in their size and appearance. No matter what the type of wetlands they all have three common characteristics: wetlands are periodically flooded or saturated with water, their soil is hydric, i.e. contains lots of moisture and the wetland supports hydrophytes, i.e. plants that grow in or on water.
When we think of wetlands, geology doesn't usually come to mind. Yet, geology plays an important role in the wetland development and the three characteristics listed above. Water accumulates in areas where it cannot penetrate the earth below. Some rocks, such as granite, shale and slate are naturally impervious to water . On the other hand, porous rocks can become impermeable if their pores become filled with fine particles from soil or sediments. Clay, for example, consists of very small particles that are easily carried long distance by moving water. Clay can potentially block up the pores in underlying rock and create a waterproof barrier that allow wetlands to develop.
The landscape also plays a large role in the ability of water to accumulate in an area. Topogenous wetlands are the most common and occur where water naturally accumulates such as hollows and valleys. Soligenous wetlands are similar to topogenous wetlands in that they also lie in hollows but the water source comes from springs. Flood plain wetlands also depend on the landscape and occur in river valleys where the adjacent land is low, broad and flat.
Geology also plays a role in the chemistry of the water that flows through a wetland since the water is affected by the rocks and sediments in the area. The water in a wetland is a source of nutrients for the wetland plants and wildlife . Calcium, for example, will be present in water that has passed through limestone. Nutrients are present in the wetland waters as a result of drainage from the adjacent land. Particles from eroded rocks, dead plant matter can enhance the water nutrients but drainage from industry and sewage can be detrimental to its nutritional value.
THREATS TO WETLANDS
Despite their importance, many wetlands have been destroyed. In fact, over half of the wetlands in the US have been lost since the 1700s. Threats to wetlands include both natural and human. Natural causes, include erosion, drought, and overgrazing by wildlife. Manmade threats include wetlands being drained and filled for development or being used as dumping sites. Many species of wildlife depend upon wetlands for existence and habitat degradation has been a leading cause of species extinction.
To earn credit for this Earthcache, please email me with the answers to these questions. Please do not include answers in your visit log. Answers can be found on the interpretive signs WITHOUT getting off the wooden path.
1. Name two important functions of a wetland.
2. Based on the surrounding geology, what type of wetland do you think this is? (Topogenous, Soligenous, or Flood Plans)
3. In addition, please include any wildlife sightings or other observations that you experienced during your visit.
For those that are interested, this Nature Center was certified as an Arboretum in 2008, and has since received recertification for 4 more years. For a list of trees and their GPS coordinates, click here. For a map of the Nature Center, including the location of the trees listed in the previous link, press here.