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(11) Solid Earth. The student knows that the geosphere continuously changes over a range of time scales involving dynamic and complex interactions among Earth's subsystems. The student is expected to: (b) explain how plate tectonics accounts for geologic surface processes and features, including folds, faults, sedimentary basin formation, mountain building, and continental accretion; •Students understand how tectonics affect topography (c) analyze changes in continental plate configurations such as Pangaea and their impact on the biosphere, atmosphere, and hydrosphere through time; (d) interpret Earth surface features using a variety of methods such as satellite imagery, aerial photography, and topographic and geologic maps using appropriate technologies Vocabulary: Orogeny As you have already learned, tectonic processes originate within the planet and produce movements of the Earth's crust. There are basically two types of pressures exerted on the crust: • Compression has a tendency to shorten the Earth's surface ,resulting in the wrinkling of the crust. What type of plate boundary may this process occur at? • Tension causes the crust to crack or fracture, while pulling it apart. Tension tends to stretch or expand the surface. What type of plate boundary may this process occur at? Folding refers to the wrinkling of the crust which occurs because of slow lateral compression. When layered flat strata are subjected to compressional forces, they are bent and deformed. Too much bending creates a break, or a fault. By far, most of the Earth-forces are compressional. Fold patterns may be simple or very complex in form, due to the varying intensity of the tectonic forces that produced them. Either way, they leave clues behind for geologists to interpret and discover their origins. What are the two types of forces at work on the planet’s surface? What types of plate boundaries do you associate with compression forces? What types of plate boundaries do you associate with tension forces? Compression forces cause f__________ of sediment, and f__________ appear when too much of this occurs. Various shapes and forms of folding are the following: Monocline: The simplest type of fold. It involves only one inclination of the rocks. In a monocline the fold is bent in one direction only. Anticline: When the pressure exerted on a rock is not great, a series of simple folds are produced. In such folds the arches or up-folds, or crests, are called anticlines. Syncline: In a simple fold, the troughs or down-folds are called synclines. The sides of the folds between the anticlinal crests and synclinal troughs are called the fold limbs. Recumbent Fold: A fold in which the limbs (waves) are largely horizontal. Geologically speaking, it is inferred that these folds were at one time vertical, and through extreme geologic upheaval, have been “upended”. When rock strata are strained beyond their ability to fold, and retain their solid state as a unit, they fracture, or break. When a fracture occurs and the rocks are displaced on either side of it relative to one another, the result is known as a fault, and the process is faulting. •Faults often occur in groups along a fault zone. Some faults displace rocks up and down. This is called vertical displacement. •Some faults cause lateral displacement or sideways movements. When there are sudden slippage movements, it generates earthquakes. A single fault movement may result in slippage ranging from a centimeter to about 15 meters. Such slippage may occur in quick succession or may occur after gaps of several decades or centuries. The cumulative displacement may involve as much as hundreds of kilometers. Type of fold represented in this photo: The crests of this fold are known as: The troughs in this fold are known as: The simplest fold is known as a: The tension fault or normal fault: A normal fault occurs where tension causes fracture in rocks that are being pulled apart. The rock above the fault plane moves down relative to the rock beneath the fault plane. The reverse fault or thrust fault: Reverse fault occurs where compressional force causes the upper block of rock to be pushed over the lower. As a result of compressional forces there is shortening of the crust. The strike-slip fault: A strike-slip fault is a fault on which the two blocks slide past one another. These faults are identified as either right-lateral or left lateral depending on whether the displacement of the far block is to the right or the left when viewed from either side. The San Andreas Fault in California is an example of a right lateral fault. A _________ fault, or normal fault is caused by tension forces, pulling the pieces apart. A ________ fault, is the result of compression forces, pushing the pieces together. The _____________ fault is the result of lateral movement. Strike-slip faults form along ____________ plate boundaries. SEDIMENTARY BASIN FORMATION Sedimentary basins are created by depressions (dips) in the surface of the lithosphere associated with tectonic processes. These topographic and bathymetric (beneath the water) basins are subsequently filled by sediment, leading to further subsidence and sediment accumulation. Sedimentary basins are important, because petroleum is most often found in such locations. A sedimentary basin is a depressed area of the Earth’s crust where tiny plants and animals lived or were deposited with mud and silt from streams and rivers. These sediments eventually hardened to form sedimentary rock. The soft parts of plants and animals, exposed to heat and pressure over millions of years, gradually changed to oil and natural gas. Coal is formed from the remains of ancient fern-like trees that died in swamps, and were compressed over the millennia. Temperature, pressure and compaction of sediments increase at greater depths. MOUNTAIN BUILDING: OROGENY The terms orogeny and orogenesis involve tectonic processes that result in the formation of mountain chains. Mountain building most commonly involves the collision between two continental lithospheric plates. Because continental plates are of relatively equal density, when they converge, they crinkle up. These are known as “folded mountains”. When the plates carrying Africa and Saudi Arabia, along with other smaller plates, collided (from the south) with Eurasia in the north, the Alps formed. When these boundaries form subduction zones, most often, volcanic mountains arise, such as the Andean orogenics. It results from the subduction of the oceanic Nazca plate underneath the South American continent. Collision follows subduction of oceanic lithosphere beneath one continent. Topographic features are found ___________ ___________ means the “origin” of mountains. Bathymetric features are found____________ Describe the two different types of mountains, and what types of plate boundaries they may form along. Give examples of each. Sedimentary basins are especially important because this is where ________________ form. CONTINENTAL ACCRETION Accretion is a process by which material is added to a tectonic plate or a landmass. There are two possible ways Amazon Alluvial Deposit this may happen. •Tectonic Accretion: Volcanic island arcs or seamounts may collide with the continent, and as they are of relatively light material, they will often not be subducted, but are thrust into the side of the continent, thereby adding to it. •Landmass Accretion: This involves the addition of sediment to a coastline or riverbank, increasing land area via erosion and deposition. The most noteworthy landmass accretion is the deposition of alluvium, often containing precious metals, on riverbanks and in river deltas. Give an example of tectonic accretion. Give an example of landmass accretion. SUPERCONTINENTS Pannotia; a time of great glaciation Formation of supercontinents, such as Rodinia, greatly influences climate. Climate influences life. Since Rodinia formed during a time when life consisted only of bacterial forms, such as stromatolites, it must have been a vast and desolate place. Life had not yet colonized land. The eight continents which made up Rodinia later reassembled briefly into another super continent Pannotia, and again into Pangaea. Rodinia produced some significant changes in the Earth. It was the largest landmass to have existed up till that time. It significantly changed ocean currents, which may have led to snowball Earth later in the Cryogenian. ENVIRONMENTS The formation of a supercontinent can dramatically affect the environment. The collision of plates will result in mountain building, thereby shifting weather patterns. Sea levels may fall because of increased glaciation in mountains and continental interiors. They may also rise if there is excessive glaciation causing isostatic pressure in the mantle. The rate of surface weathering can rise, resulting in an increase in the rate that organic material is buried… and the formation of sedimentary basins. The formation of a supercontinent insulates the mantle. The flow of heat will be concentrated, resulting in volcanism and the flooding of large areas with basalt. Increased volcanism leads to increased greenhouse gases, and global warming. Notice here that the hottest areas on the planet are right over Pangea during this period. CAMP, or Central America Magmatic Province Why didn’t the formation of the supercontinent Rodinia influence the biosphere as much as Pangea did? How does mountain building due to continental collision affect climate? BIOSPHERE Plate tectonics recycles water, carbon and nitrogen, creating an environment that is perfect for life. Land and sea barriers generated by continental drift have influenced distribution of life on the Earth by restricting movements of both plants and animals. It makes oceans open and close, mountains rise and fall and continents gather and split. Organisms that arose and diversified on an ancient landmass, such as Gondwana, were prevented by large sea barriers from Every 500 to 700 million years, tectonics colonizing other landmasses. brings the continents together to form a supercontinent. Diversity of life is a consequence of isolation. Less isolation, means less When these supercontinents slowly break diversification. This occurs during up, separating landmasses forming Breakup Formationand Breakup of shallow seas, evolution goes into overdrive, supercontinent formation, producing both of of Pangea Pangea one continent and one ocean with one Pannotiacountless new species which forming Panthalasacoast. Because genes (heritable units of colonize the new habitats. organisms) are allowed to “flow”, evolution slows down. Tectonics can move a continent from a tropical to a polar latitude, where the organisms will experience new patterns of competition. Break-up events result in the tremendous proliferation of diversity of life forms. Gene What does each of these animals have in common? Not only are they all marsupials, or special mammals who birth embryos that are nurtured within pouches, but they all are currently found in the wild, only in Australia. They began evolving near the breakup of the supercontinent, Pangea, which went on to form Laurasia and Wombat Gondwana. BIOSPHERE During in the Triassic Period and later, the break up of Pangea played a significant role in the Devil evolution of all marsupials, especially those in Tasmanian the Americas and Australia. They were unable to compete in Asia and Europe, and became extinct there. Wallaby Tectonics provides an explanation for the vast number of different species of marsupials in Australia, but the relative rarity of marsupials elsewhere. Marsupials were able to adapt and compete successfully only in Australia. Evolutionarily, adaptation is what it’s all about! Opossum: Only remaining marsupial in North America Formation of supercontinents often is accompanied by _________ diversification of life forms, due to increased gene flow. Break-up of supercontinents leads to ___________ , which influences huge diversification events. What types of barriers do plate tectonics provide that influence evolutionary events? Why are there currently more marsupials on Australia than on any other continent? ATMOSPHERE AND HYDROSPHERE Throughout the Pangea period, due to the reconfiguration of the continents and oceans, global atmospheric circulation patterns changed. Atmospheric warming was caused by Atmospheric Circulation: expansion of magma beneath Pangea. During Pangea Carbon is cycled tthrough tectonics as well. Carbon dioxide is released into the atmosphere by volcanic activities. CO2 will warm up the air, and cause more seawater to evaporate. Acidic rain reduces the amount of CO2 by producing carbon-containing minerals, which is carried into the mantle by plate tectonics, and eventually returns to the atmosphere through volcanoes to repeat the cycle again. Interestingly, this planetary self-help method of climate regulation may not work very well if the CO2 released by human activities becomes too much for the slow process of plate tectonics to handle! During the time of Pangea, global circulation patterns were affected. When the Australian and South American continents broke away from Antarctica approximately 38 mya, oceanic currents in the newly formed Southern Ocean created a circumpolar current. This in turn led to atmospheric currents that rotated from west to east. Both these atmospheric and oceanic currents stopped the transfer of warm tropical air and water to the higher latitudes. This ultimately led to the cooling of the Antarctic continent. HYDROSPHERE AND ATMOSPHERE The thermal plumes that arise during As you saw on the last slide, there is an unavoidable connection between atmospheric supercontinent in: When the circulation, and oceanic circulation patterns. They both affect buildup climate result greatly. • warming atmospheres, results North and South American continents joined around 3 mya forming thewhich isthmus of in: sea level rise due thermal expansion Panama, (historically known as the Isthmus of•Darien) this had thetoeffect of stopping water, which equatorial currents passing from the Atlantic toofthe Pacific. . results in: It has been shown that this strengthened the Gulf • the melting of the ice sheets, changing Stream by diverting more equatorial (warm) the weight on the continents beneath, currents northwards towards Europe. changing isostatic pressure, which results in: In doing so, warm waters at high latitudes led to • localized sea-level change as the land increased evaporation and therefore atmospheric rebounded with the removal of ice, which moisture. results in: •increased precipitation as snow and ice Today, evaporation in the tropical Atlantic and Caribbean leaves behind saltier ocean waters and over Greenland, ultimately leading to a puts fresh water vapor into the atmosphere. build up of the ice cap, which results in: • average albedo increase, which leads to Trade Winds carry the water vapor westward further global cooling. across the low-lying isthmus, depositing fresh This is cyclical in nature, as seen by this water into the Pacific through rainfall. As a result, graphic representation of global the Atlantic is saltier than the Pacific temperatures through geologic timeapart. Sea level is generally lower during the time of supercontinents, and higher when they break This is because the age of the oceanic lithosphere provides a major control on the depth of the ocean basins, and therefore on global sea level. Let’s take a look at the cycle. THE FUTURE In the next 50 to 200 million years, all of Earth’s continents will be once again pushed together into a supercontinent. The proposed supercontinent, Amasia, will be centered around the North Pole. This conclusion comes from a computer model that shows the slow movements of the continents over the next several millions of years. How will this supercontinent affect global circulation patterns, and climate? Will humans be here to see it? Considering the fact that the greatest mass extinction in Earth's history happened at the same time Pangaea formed 250 million years ago, the formation of a supercontinent in the future may eventually cause extinctions on a similar scale. The lessons from these vast geologic and geographic changes is both simple and exceedingly complex. As you’ve seen, the opening and closing of seaways has a profound influence on the distribution of fresh water, nutrients, and energy in the global ocean. The coupling of these changing oceans with a changing atmosphere inevitably means a changing climate. Describe how CO2 is recycled in plate tectonics, and how it plays a role in planetary temperatures. What is the danger of increased human CO2 formation? How did the break-up of Pangea, particularly Antarctica from South America and Australia, lead to a colder climate for Antarctica? How does a strengthening Gulf Stream influence global temperatures? Which ocean is saltier, and why? When did this happen? SATELLITE IMAGERY Satellite imagery consists of photographs of Earth made by means of artificial satellites. Satellite images have many applications including meteorology, geology, forestry, intelligence and warfare. Images can be in visible The and transceiver, turn, relays colors in other in spectra, suchthe as message infrared. via a Mt. Cotopaxi satellite data link to a control centre onshore. There are also elevation maps, usually made by radar images. Interpretation and analysis of satellite imagery is conducted using specialized remote sensing applications. Some of the first image enhancement of satellite photos was conducted by the U.S. Government and its contractors. Satellite imagery is also used in seismology and oceanography in deducing changes to land formation, water depth and sea bed, by color caused by earthquakes, volcanoes, and tsunamis. Satellite photography can be used to produce composite images of an entire hemisphere or to map a small area of the Earth, such as this photo of the countryside of Haskell County, Kansas, United States. ARIEL PHOTOGRAPHY Aerial photography is the technique of capturing photographs of the land from an elevated location. This type of photography usually refers to photographs which are taken when the camera is not supported by a ground-based structure. The camera in aerial photography may be hand held or mounted, and photographs may be taken by a photographer, triggered remotely, or triggered automatically. Aerial photography can produce some very inspirational photographs that provide us a beautiful view of our Earth’s surface from a perspective that we never see. Unlike maps, which portray the physical and cultural landscape with generalized symbols and colors, aerial photography reveals the terrain as it exists in nature. All buildings, bridges, roads, urban and rural areas, and other man-made features are depicted as they were at the time of photography. Physical features, such as vegetation type and distribution, river widths and courses, shorelines, landslide areas, etc. are shown with detail that no map can depict. Aerial photography is extremely useful both for site evaluation and for regional analysis, as well as for historical perspectives. It is used by engineers, architects, city and regional planners, geographers, geologists and historians. How can we use infrared light in satellite imaging? Describe passive vs. active satellite sensing. Aerial photography can be accomplished both by an actual photographer, or _____________, using robotics. What are two positives of using aerial photography over some other surface interpretation technique? TOPOGRAPHIC MAPS A topographic map, also known as a topo map, is a map which shows changes in elevation by using contour lines. Contour lines are imaginary lines that join points of equal elevation on the surface of the land above or below a reference surface such as average sea level. Contour lines make it possible to show the height of mountains, depth of the ocean bottom, (on a special topo map known as a bathymetric map) and steepness of slopes on a topo map. To visualize what a contour line represents, picture a mountain (or any other topographic feature) and imagine slicing through it with a perfectly flat, horizontal piece of glass. The contour interval is the difference in elevation between two adjacent contour lines on a topo map. You can determine the contour interval by counting the number of contours between labeled index contours and then by using this formula: For example, on the map shown here, you can see that there are 15 contour lines between the 2400 index contour and the 1800 index contour. So the contour interval is calculated as follows: Contour Interval: 40 ft. Close line =Steep Slope The steepest slopes on the map can be seen by looking for lines that are very close Contour lines bend upstream when crossing a together. Since each line represents a river changepossible in elevation of a set (20 Highest elevation of aamount hillat the Since contour lines must remain same meters in this example), lines that are close The highestthey elevation a hill when can bethey calculated elevation, mustofbend crossby finding together indicate steepline gradients. The area the last (highest) contour that hill, andso then riverbeds. A riverbed dropsondownward, thefiguring circled in red very steep, because has out the next lineis that would be drawn. Theithighest contour line must bend uphill to stay at the same possible elevation of theclose hill is just below the value of many lines crowded together. elevation. The highlighted lines show that Depressions are shown by small marks that next line. The highest possible elevation of the the hill direction of thearrow Mill must be line northeast. pointingby inward offRiver indicated the isthe 239contour meters. The lineis indicated map is 220 meters. TheThe next The last arrow pointingontothe a depression, or hole. line wouldline be 240 (remember that the contour contour withmeters the marks, or hatchers, has the interval is 20 meters). Since is no meter line, same elevation as the linethere before it.240 In this case the the hill cannot be higher than 239 meters! hatchered line has a value of 140 meters, and the depression must be less than 140 meters. One of the most important sources of information on a topographic map is the date of revision. Although large scale topographic features (such as mountains) take millions of years to be formed and eroded, other features, such as volcanoes and river channels, may change on a much more rapid scale. • volcanic eruptions, flooding, landslides may alter topography significantly, roads are added or go out of use, etc. Present Day GEOLOGIC MAPS Geologic maps, like all maps, are designed to show where things are. •Unlike the maps we are used to which show the distribution of roads or rivers or county boundaries, a geologic map shows the distribution of geologic features, including different kinds of rocks and faults. •A geologic map is usually printed on top of a regular map (called a base map) to help you locate your location on the map. The base map is printed with light colors, so it doesn’t interfere with seeing the geologic features on the map. •The geology is represented by colors, lines, and special symbols unique to geologic maps. The most strikingthese features of geologic maps you are its Understanding features will allow tocolors. Each color represents a different geologic A geologic is a volume of a certain kind of rock of a understand much unit. of the geologyunit shown in given age range. So a sandstone one age might be colored bright orange, while almost any standard geologic of map. a sandstone of a different age might be colored pale brown. Although the geology of every area is different, all geologic maps have several features in common: colored areas and letter symbols to represent the kind of rock unit at the surface in any given area, and lines to show the type and location of contacts and faults. The geology of an area has a profound effect onQalmany things, Holocene Period: - Quaternary alluvium from the likelihood landslides, Quof - Quaternary undivided Period: Qt groundwater - Quaternary terrace toPleistocene the availability of deposits inCretaceous wells, from the amount of Chalk Period: Kau - Austin Kef earthquake, - Eagle Ford shaking suffered in an Kwb - Woodbine to the presence of desirable Kgm - Mainstreet & Grayson minerals, from the way theon map) (undivided Kpd - Denton, Weno Kpp landscape is shaped to the kinds & Pawpaw Pawpaw of plants that grow best there. Understanding the earth underneath is the first step in understanding the world around Kfd - Duck Creek & Kfw us. So what’s the geology Fort Worth like in Fort (undivided on map) Worth your neighborhood? Kki - Kiamichi Kgw - Walnut & Goodland (undivided on map) Kpa - Paluxy sand ___________ on topographic maps are lines that join points of equal elevation. One contour line is at 4,000 meters, and another, higher up the mountain, is at 5,600 meters. There are 8 contours crossed between the two. What is the contour interval? On a contour map, the ___________ the lines are together, the _____________ the slope. Calculate the contour interval on this map, in meters, and determine the highest possible elevation of hill C. How are depressions depicted on a contour map? Why is the revision date on a topographic map of an area depicting rivers and volcanoes more important than on topographic maps showing other areas? What feature makes it easier to interpret you location on a geologic map? Describe the geological foundation of our area, and determine within which geologic period it was laid.