Major river systems. There are many large rivers in Africa. The distribution of the river network across the continent is uneven. (Explain why.) About 1/3 of the continent's surface belongs to the territory of internal drainage.
The longest river in the world is the Nile (6671 km). It begins on the East African Plateau and flows through Lake Victoria. In the upper reaches, the river, rushing down the gorges, forms rapids and waterfalls. Having reached the plain, it flows slowly and calmly and is called the White Nile. Near the city of Khartoum, the river merges with the waters of the largest tributary - the Blue Nile, flowing from the Ethiopian Highlands. After the confluence of the White and Blue Nile, the river becomes twice as wide and receives the name Nile. In the middle course, the Nile cuts through a plateau composed of hard rocks, so there were rapids that interfered with navigation. Now, thanks to the dam built near Aswan, navigation conditions have been improved. In the lower reaches the river flows calmly. When it flows into the Mediterranean Sea, it forms a large delta, in the place of which several tens of thousands of years ago there was a bay of the Mediterranean Sea.
In the past, the Nile was a mystery to North Africans and Europeans. They saw that a deep river flows from the desert, which loses a lot of water through evaporation and seepage into the ground, but does not dry out, although there is almost no rain there. They explained this by the intervention of a supernatural force and deified the river. (How do you explain this phenomenon?) The Nile is of great importance in the economies of the countries through which it flows. Since ancient times, river waters have been used to irrigate fertile fields, thanks to the silt brought by the Nile. To regulate flow and irrigate fields, dams and canals were built in certain sections of the river, many of which have existed for millennia.
The deepest and second longest river in Africa is the Congo (Zaire) (4320 km). In terms of water content and basin area, it is second only to the Amazon. The river crosses the equator in two places and is full of water. all year round. Congo (Zaire) flows along the ledges of plateaus, so it has many rapids and waterfalls. Navigation is possible only in certain areas. The river, in contrast to the Nile, does not form a delta; its muddy fresh waters extend far into the Atlantic Ocean in a wide stream.
The third largest river in Africa by length and basin area is the Niger. In its middle reaches it is a flat river, and in its upper and lower reaches there are many rapids and waterfalls. A significant part of the river crosses arid areas, so it has great importance for irrigation; for this purpose, dams and irrigation canals were built on the river.
The Zambezi is the largest river in Africa that flows through Indian Ocean. (How do you explain this?) Here is one of the world's largest waterfalls - Victoria Falls. The river falls in a wide stream (1800 m) from a ledge 120 m high in a narrow gorge that crosses its bed. The roar and roar of the waterfall can be heard for many kilometers. The water, rushing down, raises giant columns of tiny splashes hundreds of meters up. Reflecting in them Sun rays form a colorful rainbow. Locals call the waterfall “thundering smoke.” Below the waterfall, dams, hydroelectric power stations and a reservoir were built.
Lakes. Almost all large lakes Africa is located in the fault zone of the East African Plateau. Therefore, their basins have an elongated shape. These lakes are usually bordered by high and steep mountains. They have great depth and considerable length. Thus, Lake Tanganyika, with a width of 50-80 km, stretches 650 km in length. This is the longest of all freshwater lakes in the world. In depth (1435 m), Tanganyika is second only to Lake Baikal. The mountains framing it rise up to 2000 m.
Lake Victoria is the largest in Africa by area. Its basin is not located in a fault, but in a gentle trough of the platform. Therefore, the lake is shallow (average depth 40 m), its shores are flat and rugged. Hurricane-force winds, which often accompany thunderstorms, cause severe storms on the lake.
Lake Chad is shallow, depth 4-7 m. Its area, depending on precipitation and the flood of inflowing rivers, changes sharply, sometimes almost doubling during the rainy period. The shores of the lake are very swampy.
The importance of rivers and lakes in the life of the population. In parts of Africa where there is little rainfall, inland water is used for irrigation. The Nile, Niger, and Zambezi rivers are especially important in this regard. Along the banks of the Nile, almost across the entire Sahara, stretches an oasis with fertile lands irrigated with Nile water. African rivers are rich in hydroelectric power. Their reserves are especially large in the Congo River basin (Zaire). Many rivers and lakes serve as waterways. The rivers and lakes contain abundant fish, which are important in the diet of Africans. By fish catch in fresh waters Africa is second only to Asia.
The only source of water supply in areas with a tropical desert climate is groundwater.
Scientists' calculations have shown that groundwater reserves in the central part of the Sahara are enormous and sufficient for growing crops and gardens.
Target: conduct a comprehensive description of the river based on field research data and various sources of information.
Equipment and materials: water thermometer, thermometer, compass, pencil, notebook, atlas, map or atlas of your area, blank plastic bottle, float, glass, ruler, camera.
Tasks: determine the nature of the river flow and water properties on the ground, prepare a comprehensive description of the river based on the study of various sources of information.
Progress:
Attention. Practical work tasks are completed independently. Below is the finished practical work using the example of r. Volga in Astrakhan. All characteristics of water properties are given as of October 26. Also in the description of tasks are given practical recommendations for work to be done by students from other regions of Russia.
Before going out on field research, listen carefully to all the teacher’s instructions, repeat the rules of safe behavior, and read the safety instructions on page 3 of the workshop again.
Carry out a local description of the river closest to your home (school) and the properties of its water.
River name - Volga.
♦ Measure the air temperature at the location where you are studying.
Air temperature in C - +14°.
♦ Use a water thermometer to measure the temperature of the water in the river. To do this, immerse the water thermometer in water for at least 5 minutes. Record the data in the table.
In practice, you can use data from numerous online meteorological services to perform tasks to measure air and water temperatures.
♦ Draw a conclusion about the difference in temperature between water and air.
Temperature upper layers water is always lower than air temperature.
♦ Determine the transparency of water in the river in two ways indicated in the workshop.
Find your way with a compass. Determine the direction of the river flow at your research site. Record the result in the table.
Determining the direction can also be done using a regular map or online Google or Yandex maps.
Table “Properties of river waters”
Using data from additional sources of information, prepare a comprehensive description of the river under study.
♦ Origin of the name. According to one version, the name of the river comes from the ancient Slavic word Vlga, which means moisture.
♦ Length, through which countries, regions it flows, through which cities. The Volga River flows through the European part of Russia, through several regions and republics. On the Volga River there are many big cities: N. Novgorod, Samara, Kazan, Volgograd, etc.
♦ Paste a photograph of the river taken during field research. Indicate the location and date of shooting.
♦ From the list provided, select examples of the use of the river you are researching in economic activity(rafting of felled timber, irrigation of fields, recreation areas, rest houses or sanatoriums are located on the banks, fishing, spring drinking water for the city (village, town), obtaining electricity). Irrigation of fields, location of recreation areas, fishing, source of drinking water for the city (for Astrakhan).
♦ What is the significance of the river to your family. Do it yourself.
♦ Find the river you are studying on the maps and determine which ocean drainage basin it belongs to. The Volga does not belong to any drainage basin.
Good day to all! In this post we will talk about the types geographical maps. I have previously written a short article about, but now we will talk about this in more detail.
Since ancient times, in order to display and transmit information about the surface of the Earth to other people, people have created maps.
Today maps are part of our Everyday life. We encounter them in weather forecasts, in guidebooks, when planning a trip and on the road.
We are best known general geographical maps. Such maps show the main elements of the area (vegetation, relief, settlements). Thematic maps focus on individual elements, for example, or temperature.
Maps are constantly updated to reflect constant changes, such as new borders, demolition of old buildings, road construction... In the 1990s. after the collapse of the USSR, cartographers had to revise political maps of Eastern Europe and the former USSR.
Geographical atlas is a systematic collection of geographical maps. The main feature of a modern atlas is the internal unity of all the maps that are included in it.
This is achieved by using comparable projections, symbols, scales, general principles design, methods of depiction, etc. It is believed that the ancient Greek scientist (2nd century AD) compiled the first geographical atlas.
Atlases include general geographical maps of the world and individual regions, and individual thematic(climatic, population, economic maps, etc.)
Regional and national boundaries are displayed, as well as the names of administrative and political units, and other major population centers. Each state and each administrative-territorial unit is painted in different colors.
Irregularities on the surface of the Earth on modern physical (relief) maps, most often shown using a hypsometric color scale (shades of blue indicate the seabed, brown - mountains, green - lowlands).
The relief image is given additional plasticity and clarity by shadow shading and shading. In some cases, a photorelief is applied to the hypsometric image to convey shadow plasticity.
The position of individual peaks relative to sea level is shown by elevation marks.
Topographic maps also refer to general geographical, since they depict not only elements of hydrography and relief, but also artificial structures, including communications and settlements, superimposed on the natural landscape.
For example, on fairly detailed topographic maps at a scale of 1:50,000 (1 cm 500 m), in addition to the socio-economic and natural objects of the area with all their inherent quantitative and qualitative features and placement characteristics using contours (lines usually Brown, which connect points with the same height) the relief is shown.
Of course, there are maps on a larger scale, including city plans, which show individual buildings, private houses, gardens...
IN modern society general geographical maps(in particular, topographical) are finding more and more wide application. For example, such cards are used in orienteering on the ground.
This sport originated in Scandinavia, and it requires the ability to recognize map elements on the ground, determine the direction (azimuth) of movement, etc. Navigation maps of the coastal zone are used in sailing.
Thematic maps contain information about the structure, location, weather, etc. Such cards are divided into several types.
On isolinear maps widely used different types lines that connect points with the same size of a certain element.
On synoptic and climate maps, areas with the same pressure are connected by isobars, with the same temperatures - by isotherms, and with the same precipitation - by isohyets.
On many thematic maps to express quantitative characteristics Conventional coloring and designation are used.
For example, on population maps, the urban population is shown by small circles of different diameters and the degree of their concentration.
Application on cartograms different colors or different saturation of the same color for painting individual areas directly corresponds to a quantitative indicator of a certain characteristic (crime level, birth rate, population density).
The attention of users of such maps is focused on statistics - the main element of the cartogram.
Topological maps are very visual. On such maps, migration or trade flows are shown with arrows or lines, the width of which reflects the intensity of the process.
Very often, topological maps are compiled without observing the image scale, this is in order to facilitate the perception of the main topic.
For example, for a passenger in transport route schemes, the main thing is to quickly find desired station and determining the route.
Also many maps display results scientific research. For example, geological maps show the structure of a certain area earth's crust, such maps are used by geographers, geologists, and they are also used when laying iron and highways, during the construction of buildings.
On geochemical maps concentrations shown chemical elements V rocks, on soil maps- types . Epidemiological maps highlight the areas of certain diseases, this helps scientists determine the causes of these diseases.
The capabilities of maps are largely limited by their scale - the degree to which lines and distances on the map are reduced in comparison with their actual sizes on the ground.
The capabilities of the map are limited in many respects by its scale - the ratio of the size of the object shown on the map to its actual size.
To show a river or road to scale on a map, one would have to draw very thin lines, so thin that they could only be seen under a microscope.
On a 1:10,000 scale map, a two-millimeter line would correspond to 20 meters, and on a 1:250,000 scale map it would correspond to 500 meters.
This is why cartographers very often simplify some elements and convey only their characteristic outlines (for example, without trying to accurately depict every bend and width of the river).
The limited scope of many details is another drawback of many maps. For example, on 1:50,000 topographic maps, wooded areas and buildings are shown, but are omitted sewer network and underground passages.
However, many maps contain a large amount of varied information. Geological maps with the help of symbols and different colors give physical characteristics relief-forming rocks and show their structure.
Geologists, by comparing the outlines of landforms with the boundaries of different geological layers, have the opportunity to determine the nature of their occurrence and the location of their emergence to the surface.
It is very important to be able to read a map, including understanding what the symbols on the map mean on the ground.
For example, the absence of surface drainage in a rainy area may suggest to geographers that the map depicts a limestone landscape, and therefore surface water go into underground voids.
The emergence of springs on the surface, which are located in one row, indicates the presence of a boundary between waterproof and aquiferous rock, which delays the flow of groundwater.
The method of space mapping has been widely used recently. The essence of this method is the compilation of thematic and topographic maps directly from space survey data.
This mapping method is highly economical. It is especially effective when updating and compiling maps of territories that are poorly studied, replenishing their content, showing those phenomena that are visible only from great heights (global faults, for example), compiling maps on specific date(synoptic maps), mapping the dynamics of the phenomenon.
The use of geographic information systems (GIS) is latest achievement cartography. GIS is a computer technology for analyzing and mapping real-world objects, as well as events occurring on our planet.
The technology combines traditional database operations, such as statistical analysis and query, with the rich visualization benefits of geographic analysis that a map provides.
All these capabilities distinguish GIS from other information systems, and also provide unique opportunities for its application in wide range tasks that are associated with the forecast and analysis of phenomena and events in the surrounding world, with the identification and understanding of the main causes and factors, as well as their possible consequences, with the planning of strategic decisions and the current consequences of the actions taken.
In almost all areas human activity GIS is used - from the analysis of such global problems, such as reduction of forest land, overpopulation, natural disasters, pollution of the territory, before solving particular problems, such as selection optimal location a new office, finding the best route between points, laying a pipeline across the area, searching for a house by address, a variety of municipal tasks.
In cartography, not so long ago they began to use world system coordinate determination, which uses satellite signals.“GPS” is a global navigation system, also known as “Navstar” (Navigation System with Time and Ranging), designed to transmit navigation signals that can be simultaneously received in all regions of the world.
The first regular orbital constellation of the system deployed from June 1989 to March 1994: 24 spacecraft were launched into orbit. In 1995, GPS was finally put into operation.
Maintenance and operation are carried out by the Ministry of Defense. All over the world the system is used to solve both military navigation problems and civilian ones.
The GPS receiver allows you to determine the speed of an object, exact time and its (latitude and longitude).
The procedure for determining coordinates on the ground has become accessible and simple thanks to the advent of inexpensive GPS receivers, and this also gave impetus to the development of electronic cartography systems.
Nowadays, this system is used in aero and sea navigation, and in geodesy. The geographic information service allows you to plot a route based on computer processing of geographic data in digital form.
Thus, we looked at the types of geographical maps that are constantly being improved and become more detailed and accurate, and this is very good for studying our Earth and for helping people navigate 😉
