Geology and Landform in Watershed Management

1. Part 2. The watershed inventory Lecture 6. Geology and landform

2. Bedrock • Bedrock underlies all watershed ecosystems. • The nature of rock determines the character of overlying soils and influences the ultimate movement of water draining through those soils. Watershed management-- 6

3. Bedrocks are formed in one of three ways: by igneous, sedimentary, or metamorphic process. Igneous rocks are formed when molten rock (magma) is pushed up through the cooler regions of the earth`s crust from deeper zones. Watershed management-- 6

4. Sedimentary rocks are composed either of fragments of mineral and rock eroded from preexisting rocks and then deposited by natural forces, or of materials precipitated from aqueous solutions. sandstone: sandy sediment limestone: shell and carbonate shales: finest clay sediment salt and gypsum: precipitation of material in solution Watershed management-- 6

5. Metamorphic rocks are created when igneous or sedimentary rocks are subjected to further heat and pressure, thus modifying their crystal structure and their physical (but not chemical) properties. Shale  slate Limestone  marble Watershed management-- 6

6. Each type of rock has its own special physical and chemical property. • The chemical properties of rocks become a significant influence on watershed soil and water chemistry. • Rock weathering can occur either through physical processes or through chemical processes. Watershed management-- 6

7. Geology structure fracture Folds faults Physical structure are important in groundwater flow and, thus, in the distribution of water within the watershed ecosystem. Watershed management-- 6

8. Surficial material • Overlying bedrock in most regions is a layer of softer sediments, or soils. • Developed gradually from the action of plants and physical forces on bedrock • Contain a mixture of eroded rock and mineral fragments and organic debris Watershed management-- 6

9. landform • Land surface can be shaped and realigned in many way by the action of ice, water, and wind. • In northern regions the force of advancing and retreating glaciers tens of thousands of years ago had an important and lasting impact on landforms. Watershed management-- 6

10. In warmer regions the action of wind and water can be important in sculpting landforms. (Heathcote. 1998) Watershed management-- 6

11. In warmer regions the action of water can be important in sculpting landforms. • In dry regions the action of wind can be important in sculpting landforms. Watershed management-- 6

12. Degree of slopes Length of slopes Shape of slopes Watershed management-- 6

13. Detailed topographic maps, available for most regions, are an excellent source of information about the degree, shape, and length of slopes. Geological database is often available in map and / or report form specific to a given area. Watershed management-- 6