LANDSCAPES

LANDFORMS Surficial features formed by: Mountain BuildingErosion/Sedimentation

Geomorphology: defined Geomorphology: The scientific study of landscapes and the processes that shape them. GEO (earth) MORPH (shape) OLOGY (study of)

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 "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 "Distinct association of landforms, as operated on by geological processes, that can be seen in a single view." - 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 INTERIOR HIGHLANDS –Areas 14 & 15 ROCKY MOUNTAIN SYSTEM –Areas INTERMONTANE PLATEAUS –Areas PACIFIC MOUNTAIN SYSTEM –Areas ALASKA –Areas 26-28

LANDSCAPE MECHANISMS

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

Endogenic Landforms

Exogenic Landforms

Exogenic 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 and Erosion

Weathering

The breakdown of the materials of Earth’s crust into smaller pieces due to Physical and Chemical Processes.

Physical 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

Frost Wedging

Frost Heaving

Plant Roots

Friction and Repeated Impact

Burrowing of Animals

Temperature Changes

Chemical Processes

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 CO 2 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

Ice Erosion Glaciers

Wind Erosion

Mass Movements Landslides, mudslides, slump and creep landslide clip.mpeg

Mass Wasting is any Down Slope Movement Due to Gravity

Soil Creep is a Form of Mass Movement

Mass Wasting

Balance Between Mountain Building and Erosion

Mechanisms Effect on Landforms Negative Feedback: When mountain building slows and erosion starts to dominate. –Elevation is in balance between the rate of tectonic uplift and the rate of erosion. Positive Feedback: When mountain summits become higher due to erosion. –Due isostatic rebound – the upward movement of the Earth’s surface due to surface erosion of valleys. i.e., Ice Berg

Feedback Between Climate and Topography Climate (Rainfall & Temperature): Affects the rate at which water dissolves minerals in rock and soil: –Rain that falls on bedrock and soil. –Infiltration of water into the soil. –Mass Wasting –Rivers and Glaciers Topography: High elevation and relief enhance the mechanical break up of rocks.

Effect of Climate & Topography on Landforms Climate –Rain that falls on bedrock and soil. –Infiltration of water into the soil. –Mass Wasting –Rivers and Glaciers Topography –Freezing and thawing –Gravity –Flow of rivers –Mechanical Weathering: high elevations –Chemical Weathering: low elevations

Models of Landscape Evolution

Originally thought to occur in two phases –Phase 1: Tectonic Uplift –Phase 2: Erosion :Present models support simultaneous tectonic processes and erosion. Key element is time –Appalachian Mountains (Older) –Rocky Mountains (Younger) –Landscapes achieve dynamic equilibrium over time

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