2 Topography refers to the elevation and relief of the Earth’s surface. Landforms are the topographic features on the Earth’s surface.Geomorphology is the study of earth surface processes and landforms.The maps above represent the same area on Earth’s surface and they show three different ways we can view landforms. The image on the far left is a clip from a topographic elevation map, the image in the middle is an infrared aerial photo, and the image on the right is the geologic interpretation of surface sediments and geomorphology. This location is interesting because it contains elements of a natural and human altered physical environment. The lake in the image, (coded blue in the topographic and geology map, and black in the infrared aerial photo) was formed by artificial damming a stream the flows through this landscape.22
4 Crustal Orders of Relief First Order or Relief:Continental Landmasses and Ocean BasinsII. Second Order of Relief:Major Continental and Ocean LandformsIII. Third Order of Relief:Genetic Landform FeaturesBeachesRivers and Flood PlainsMountains4
5 Constructive Processes Constructive processes build landforms through tectonic and depositional processes.Tectonic processes include movements at plate boundaries, earthquakes, orogeny, deformation, and volcanic activity.Deposition is the accumulation or accretion of weathered and eroded materials.5
6 Destructive Processes Destructive processes break down landforms through weathering, erosion, and mass wasting.Weathering is the disintegration of rocks by mechanical, chemical, and biological agents.Erosion is the removal and transportation of weathered material by water, wind, ice, or gravity.6
7 Folded MountainsFolding occurs when rocks are compressed or deformed and they buckle under the stress.7Table of Contents7
11 CalderaCalderas are bowl-shaped collapse depressions formed by volcanic processes.Crater Lake in Oregon is the collapsed caldera of Mount Mazama and is now filled in with water. Wizard Island is a volcanic cone in the middle of the lake. Crater Lake is the deepest lake in the United States at 1,932 feet deep!11Copyright Larry Fellows, USGSTable of Contents11
12 LakesLake: a basin (lower area) filled with fresh water, surrounded on all sides by land.Although 70 percent of the earth is covered with water, only about 2.5 percent is freshwater, in lakes and rivers.12
13 Mountain StreamsMountain streams are sourced from springs, rainfall, or snowmelt. They often contain a v-shaped valley, bedrock stream bottom, rapids, waterfalls, and a very narrow flood plain.Step–pool sequence in the MiddleSaluda River, South CarolinaThis stream is in the Mountain Bridge Wilderness Area in South Carolina. It flows over bedrock and contains numerous waterfalls and step-pool sequences.13Table of Contents13
16 DeltasDeltas form where the mouth of a river meets its ultimate base level at the ocean or sea. As the river’s velocity decreases, it loses the capacity to carry its sediment load and the resulting deposits form a delta.Deltas are very rich in fertile soil, making them excellent farming areas.The red line shows where the coast was before the delta16
18 CavernsCaverns and caves are large empty spaces where the rocks has been dissolved by carbonation.Some caves are formed by lava tubes and others are formed by the erosion.Which type would we have in Florida?Caverns and their various features form below the ground water table where dissolved minerals drip through the ceiling of the cave through fractures and joints in the limestone. Over time this mineral-rich ground water dissolves the rocks until eventually entire caverns are formed.Calcium carbonate precipitates out of the saturated carbonate solution and accumulates as deposits. Stalactites are deposits that grow from the ceiling downward and stalagmites are deposits that grow from the ground up. If the stalactite and stalagmites join they form a continuous column.Mammoth Cave in Kentucky and Carlsbad Caverns in New Mexico are two of the largest cave systems in North America and the world.Not all caves are formed by karst processes.This image of the “Chinese Theatre” in Carlsbad Caverns National Park illustrates how stalactites and stalagmites can join to form columns. Notice the person in the lower left for scale!18Table of Contents18
19 Caverns (cont.)As the water flows through the rock it chemically changes the rock, once it reaches the air of a cavern, the CO2 leave the water, turning the rock back into rock. This results in:Stalactites: cone shaped protrusions on the ceilings of caverns.Stalagmites: cone-shaped mounds on the floor of a cavern.Caverns and their various features form below the ground water table where dissolved minerals drip through the ceiling of the cave through fractures and joints in the limestone. Over time this mineral-rich ground water dissolves the rocks until eventually entire caverns are formed.Calcium carbonate precipitates out of the saturated carbonate solution and accumulates as deposits. Stalactites are deposits that grow from the ceiling downward and stalagmites are deposits that grow from the ground up. If the stalactite and stalagmites join they form a continuous column.Mammoth Cave in Kentucky and Carlsbad Caverns in New Mexico are two of the largest cave systems in North America and the world.Not all caves are formed by karst processes.19
20 SinkholesSinkholes: the water slowly dissolves the limestone rock below the surface until it eventually becomes unstable and collapses creating a sinkhole.The left is an aerial view of the Tres Pueblos sinkhole in Puerto Rico. Solution of the underlying rock caused bedrock, soil, and vegetation to collapse into the sinkhole feature. The images above are from urban areas in Florida where sinkholes damaged several homes and businesses.20Photo: USGSTable of Contents20
21 SpringsSprings are locations where groundwater emerges from the limestone and flows across the surface forming a stream or contained pool.Springs that are connected to aquifers flow year-round and support rich aquatic biodiversity.21
22 Water Table: Soil is not a solid block Water Table: Soil is not a solid block. There are spaces between the grains of sediment, filled with air or water. The point where water fills the spaces instead of air is called the water table.The water table mirrors the shape of the surface terrain, rising and falling with the hills and valleys.
23 Aquifers: water stored underground in cavern and rock systems. the
24 Beaches Coast: (coastline, seashore) where the land meets the ocean. Beaches are depositional landforms along the coastal area where sediment is transported and deposited by waves and currents.Most beaches are dominated by sand-sized quartz grains, and shells or shell fragments.Beaches often stabilize shorelines by absorbing or deflecting wave and current energy. During large storms, such as hurricanes, beaches can experience extensive erosion, and it can be years before they are replenished. Beaches provide numerous recreational activities and are a popular destination for vacationers.Photo: SCGS24
25 DunesDunes are formed as mounds or ridges of sand deposits and are then sculpted by the wind.Beach Dunes: are important to protectthe shore from storms and waves erodingaway the land.Barchan DunesTransverse Dunesslip faceWind directionWindWindSand avalancheDune movementJohn McCauley, USGS25John McCauley, USGSresources/images/lgformat/barchan.jpgTable of Contents25
26 Barrier IslandsBarrier islands, also referred to as barrier beaches, are long, narrow, depositional landforms, that form parallel to the coastline and may or may not connect to the mainland. They are the first line of protection against hurricane storm surge.The landward side of the barrier islands may contain tidal flats, marshes, swamps, lagoons, coastal dunes, and beaches.Image: NOAA26
27 Continental Shelf and Slope The continental shelf is a submerged extension of the continental crust that slopes gently outward from the modern shoreline to the deep ocean basin.On average it extends outward for about 80 kilometers (50 miles) and has an average slope of about 1 degree (2 meters/kilometer or 10 feet/mile).Ocean floor features including continental shelf and slope. This diagram provides a good illustration of how the shelf is a shallow extension of the continental crust.Source: NASA, Visible EarthA digital elevation model (DEM) of the continental shelf and slope near Los Angeles, California.
29 These rocks were deposited by moving glaciers. The glacier froze around them, then moved hundreds of miles to depositThese rocks in place they would not normally be found.Yosemite Valley is littered with glacial erratics, like the example below, perched on Lambert Dome. This erratic is quite angular suggesting it was only transported by the glacier for a short distance or amount of time.The image above is from a recently deposited glacial erratic. Notice how the erratic is still perched atop glacial ice, and there is a glacier retreating in the lower right corner of the image. The person in front of the erratic provides a relative scale for size.29Source: Wikimedia CommonsTable of Contents29
30 Resources and References Christopherson, R. W Elemental Geosystems. 4th Ed. Prentice Hall. Upper Saddle River, New Jersey.Lutgens, F. K. and E. J. Tarbuck Essentials of Geology, 8th Ed. Prentice Hall. Upper Saddle River, New Jersey.Smith, G. A. and Pun, A How does Earth Work? Physical Geology and the Process of Science. Prentice Hall. Upper Saddle River, New Jersey.30Table of Contents30
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