LANDFORMS • Surficial features formed by: Mountain BuildingErosion/Sedimentation
Geomorphology: defined GEO (earth) MORPH (shape) OLOGY (study of) Geomorphology: The scientific study of landscapes and the processes that shape them.
Geomorphology: basics • What is a landscape? • A surface composed of an assemblage of subjectively defined components. • What is a landform? • A landscape component that can be observed in its entirety "Distinct association of landforms, as operated on by geological processes, that can be seen in a single view." - Glossary of Geology "Any physical, recognizable form or feature on the earth's surface, having a characteristic shape, and produced by natural causes; it includes major forms such as a plain, plateau, or mountain, and minor forms such as a hill, valley, slope, esker, or dune. Taken together, the landforms make up the surface configuration of the earth." - Glossary of Geology
Landform Description • Landforms are described using the following terms: • Topography: The general configuration of varying heights that gives shape to the Earth’s Surface. • Elevation: Height of landscape features above and below sea level. • Contours: Lines that connect equal points of elevation which show the distribution of elevations in an area. • Relief: The difference between the highest and lowest elevations in an area.
Landform Examples • Mountain: Large mass of rock that projects well above its surroundings due to tectonic activity. • Plauteau: Large, broad, flat areas of appreciable elevation above the neighboring terraine formed due to regional uplift by tectonic activity. • Mesa: Small platueau formed from differential weathering of bedrock of varying hardness. • Anticlines • Synclines
Landform Examples • Badlands: Deeply gullied features formed from fast erosion of easily erodible shales and clays. • Cuestas: Assymetrical ridges in a tilted aand eroded series of beds with alternating weak and strong resistance to erosion. • One side has a long gentle slope. • Other side has a steep slope. • Hogback: Narrow ridges formed by layers of erosion-resistant sedimentary rocks that are tectonically turned up so that the beds are vertical or nearly so.
United States Physiographic Regions • The U.S. Physiographic Regions are based on landscape features, which are mostly controlled by the geology of the regions.
United States Physiographic Regions • LAURENTIAN UPLAND • Area 1 • ATLANTIC PLAIN • Areas 2 & 3 • APPALACHIAN HIGHLANDS • Areas 4-10 • INTERIOR PLAINS • Areas 11-13 • INTERIOR HIGHLANDS • Areas 14 & 15 • ROCKY MOUNTAIN SYSTEM • Areas 16-19 • INTERMONTANE PLATEAUS • Areas 20-22 • PACIFIC MOUNTAIN SYSTEM • Areas 23-25 • ALASKA • Areas 26-28
Landscape Mechanisms • The interaction of Earth’s internal and external heat engines controls landscapes. • Internal Heat Engine (Endogenic Process) • Plate tectonics • Mountain Building • Constructive Process • External Heat Engine (Exogenic Process) • Sun: Affects Climate (Wind, Temperature, Precipitation) • Weathering and Erosion • Destructive Process
Sedimentary Cycle is Subcycle Within Rock Cycle • Weathering: Parent rock breaks apart into smaller rocks. • Erosion: Rocks become individual grains. • Transportation: Material is transported by wind, water or gravity. • Deposition: Material comes to rest in new location and often additional material piles up on top.
Weathering • The breakdown of the materials of Earth’s crust into smaller pieces due to Physical and Chemical Processes.
Physical Weathering • Process by which rocks are broken down into smaller pieces by external conditions. • Types of Physical weathering • Frost heaving and Frost wedging • Plant roots • Friction and impact • Burrowing of animals • Temperature changes
Chemical Weathering • The process that breaks down rock through chemical changes. • The agents of chemical weathering • Water • Oxygen • Carbon dioxide • Living organisms • Acid rain
Water • Water weathers rock by dissolving it
Oxygen • Iron combines with oxygen in the presence of water in a processes called oxidation • The product of oxidation is rust
Carbon Dioxide • CO2 dissolves in rain water and creates carbonic acid • Carbonic acid easily weathers limestone and marble
Living Organisms • Lichens that grow on rocks produce weak acids that chemically weather rock
Acid Rain • Compounds from burning coal, oil and gas react chemically with water forming acids. • Acid rain causes very rapid chemical weathering
Erosion • The process by which water, ice, wind or gravity moves fragments of rock and soil.
Water Erosion • Rivers, streams, and runoff