Topic 14 – Landscape Development and Environmental Change Landscapes, or topography are the features of the Earth’s surface. There are Four main ways to characterize a landscape: 1) Slope (gradient) of the land 2) Shape of the landscape features 3) Soil properties 4) Stream drainage patterns Slope (gradient) of the Land Remember if you have a steep slope, there will be less deposition of particles there. If water flows over the steep slope (gradient), it will flow faster causing more weathering and erosion The slope of the land can be measured using the gradient equation on the front cover of your ESRT gradient = change in field value distance Shape of the Landscape Landscapes are divided into three major types 1) mountains 2) plateaus 3) plains A mountain is an area of high elevation, compared to the surrounding area or sea level. Its peak is usually thousands of feet higher than its base. They usually are characterized by distorted rock structures with faults, folds or volcanic rocks because they are usually composed of metamorphic and volcanic rocks. Cont. Shape of the Landscape A plateau is also an area of high elevation, but it has undistorted horizontal rock structure and often a more level slope or gradient. It may have steep sides if they have been eroded by a glacier or stream. Ex: Colorado Plateau in CO, Catskill Plateau in NY Cont. Shape of the Landscape A plain is usually composed of sedimentary rocks, has a low elevation and generally a flat/level surface with little slope. Ex: Atlantic Coastal Plain of Long Island, NY You can see the Landscape Region of New York on page 2 of your ESRT. Factors of landscape development Two groups of forces can change landscapes: 1) uplifting forces 2) the leveling or destructional forces Uplifting forces originate beneath the Earth’s surface. They displace the rock and raise the land, where mountains can be built. This can be done by volcanoes, earthquakes – energy is gained from the convection currents in the mantle. Factors of landscape development Leveling forces occur near the Earth’s surface. The land is leveled and lowered by breaking down rocks and transporting them elsewhere (erosion). The erosional systems can be running water, wind, glaciers, gravity or shoreline processes. The landscape process has stages: youth, maturity and old age. In youth, uplifting forces take place. In maturity, leveling forces take place and in old age, leveling forces are still dominant but less effective. Cont. Factors of landscape development Glaciers affect landscapes also and evidence from the last ice age (Pleistocene) can bee seen. Some features of glacial erosion and deposition. include: 1) mountaintops and steep slopes without much soil 2) soils with large range of particle size 3) wide U-shaped valleys 4) many lakes (finger lakes) 5) many small hills (drumlins or moraines) 6) parallel scratches on bedrock How does climate affect Landscape Development The rate at which landscape development occurs is dependent on temperature and moisture In dry/arid climate – there is little vegetation so sediments do not stay in place on steep slopes, so they get rapidly carried away. This allows an arid climate to have steep slopes and sharp angular features with sand dunes and sandblasted bedrock. Ex: Southwestern US In wet/humid climates – sediments will hold better on steeper slopes, so the landscape is typically smoother and has more rounded features. Eastern US Soil properties Looking at the soil’s permeability, porosity, particle size, etc is important. The climate affects the soil that covers the bedrock 1) Arid climates – thin soil coverings 2) Humid climates – thick and full of organic soil coverings. Drainage Patterns The drainage pattern (way in which water will flow) is mainly determined because of the resistance and structure of the underlying rock. In horizontal layers, streams will develop a random pattern If there are structures like folding and faulting, the rocks will control the directions of stream flow. Some bedrock structures are: Escarpments (cliffs) along the edge of resistant layers Ridges (narrow uplands) formed from resistant rocks in the Hudson-Mohawk Lowlands is SE New York.