Principles of geographical isobaric and isotherm diagrams and enumeration and general solutions of all question types

1. Principles of contours

1. Principle of isovalue or iso-distance

In a contour map, two adjacent Contour lines are either of equal value or equidistant.

2. The principle of low high low and high low high

Low values ​​convex to high values, and the values ​​at the convex points become lower

High values ​​convex to low values, convex The value at the position becomes higher

3. Principle of small sparsity difference and large density difference

The sparser the isoline, the smaller the difference per unit distance

etc. The denser the value lines, the greater the difference per unit distance

2. Types of contours

High school geography mainly includes: contours, isobaths, isotherms (etc. Air temperature lines, isobaric lines), isobars (horizontal isobars, vertical isobars), equal precipitation lines, equal solar radiation lines, equal salinity lines, equal pH lines, equal solar height lines, Equal phreatic level, equal pressure water level, etc.

3. Application of main contours

1. Determine the type of terrain (mountain, basin, valley, contour, ridge line, valley line, cliff) by interpreting contour lines ) The steepness or gentleness of the slope, determining the direction of the mountains, selecting the location of the reservoir dam, selecting the direction of the highway line, drawing the terrain profile and estimating the engineering earthwork, etc.

2. Determine the types of marine terrain such as continental shelves, trenches, ocean basins, ridges, submarine volcanoes, etc. by interpreting isobaths; even determine the specific sea area where the topographic map is located; determine the location conditions of the port.

3. Determine the name of the air pressure center by interpreting atmospheric isobars: such as cyclone, anticyclone, high pressure ridge, low pressure trough, and contour; determine the weather characteristics, wind direction and wind strength in different parts. Typical pressure center names can also be determined from global isobars.

4. By interpreting the atmospheric isotherms, you can determine the northern and southern hemispheres, seasons and weather, as well as the air pressure center on the continent and ocean in that season, and the prevailing direction of the monsoon (eastern and southern Asia).

5. Determine the nature of ocean currents, the locations of the northern and southern hemispheres and the east and west coasts of the continent, and the impact of ocean currents on the environment by interpreting ocean isothermal lines.

6. Determine the windward slope and leeward slope of the mountain by interpreting the constant precipitation lines and combining it with the specific terrain contours, the specific distance from the sea, the direction of the mountains, etc.

7. Interpret solar radiation contours, judge and answer the areas and causes of maximum and minimum solar radiation, the overall pattern of distribution and the impact on human beings.

8. Determine the intensity, source location and epicentral distance of an earthquake at a certain point on the surface by interpreting isoseismic lines.

9. Determine the location of ocean ridges and trenches, as well as the location and direction of seafloor rupture zones and collision zones by interpreting age contours of seafloor rocks.

10. Analyze the rules of population distribution in a certain area and the natural, historical, social, and economic factors that affect it by interpreting the population density contours.

IV. General methods of interpretation

1. Reading value - equal value difference (the numerical difference between two adjacent lines is equal or 0); change rule (this It is the basis for doing the questions)

2. Look at the density - understand the influencing factors

3. Look at the direction and shape - understand the influencing factors

4. Pay attention to the bends of the contour lines - you can add auxiliary lines to make the abstraction intuitive

(1) Contour lines

1. The basics of contour lines Knowledge

①The same line and the same height. ②The contour distance is consistent across the entire map or is 0. ③ Contour lines are closed curves but do not intersect each other, but they can overlap on cliffs. ④The density of contour lines reflects the gentle and steep slope. Slope = vertical relative height/horizontal distance ⑤The slope line indicates the downhill direction. ⑥Several special contour lines

The 0-meter line represents sea level and is also the coastline;

Below 200 meters above sea level, the contour lines are sparse and broad and flat - it is a plain terrain;< /p>

Below 500 meters above sea level, the relative height is less than 100 meters, the contour lines are sparse, and the bends are gentle - it is hilly terrain;

The altitude is above 500 meters, the relative height is more than 100 meters , the contour lines are dense, and the valley turns in a V shape, which is a mountainous terrain;

The altitude is large, the relative height is small, the contour lines are very dense at the edge, and the top is obviously sparse - it is a plateau terrain.

2. Determine terrain type

(1) Large terrain type

Plain: altitude <200m, terrain undulations are small, and contours are sparse< /p>

Plateau: The altitude is >500m, the internal terrain is less undulating, the contours are sparse, and the edge terrain is steep and the contours are dense.

Mountains: 500m above sea level, with large terrain undulations and dense contours

Hills: 200-500m above sea level, with large undulations and dense contours

Basin: There is no standard elevation. It is low in the middle and high on the surrounding sides. The internal terrain is less undulating, the contours are sparse, the edge terrain is steep, and the contours are dense.

(2) Small terrain type

Mountaintop: high in the middle, low on all sides

Valley (or depression): low in the middle, high on all sides

Valley: a place where low places bulge toward high places

Ridge: a place where high places convex toward low places

Saddle: a low land between two mountaintops, with high sides. Low on both sides, symmetrical terrain - the terrain at the saddle is very gentle

Cliff: a place where two or more contour lines overlap

Canyon: low in the middle, high on both sides, and both Places with dense lateral contours

Sand dunes: In arid and semi-arid areas, they are formed by wind deposition and appear as crescents on the contour map. According to the dune shape, the steep slope is the leeward slope and the gentle slope is the windward slope.

(3) Determine whether the slope is steep or gentle

On the same contour map, the denser the contours, the steeper the slope; the sparser the contours, the gentler the slope.

On different contour maps, the steepness and gentleness of the slope are related to the density of the contours (proportional), the size of the scale (proportional), and the size of the contour intervals (proportional) . Tangent of slope = vertical relative height/horizontal field distance

Type of slope - visibility problem: solved by making a terrain profile. If the terrain profile drawn through two known points does not have mountains or ridges If blocked, the two places can see each other; note that the convex slope (dense on the contour line is dense below) is not visible, and the concave slope (dense on the contour line is sparse on the bottom) is visible; pay attention to the requirements in the question, the landscape in the analysis picture is looking up Or visible from above.

(4) Calculation of relevant height

Calculation of altitude is based on the sea level of the Yellow Sea

Calculation of relative height Calculation of relevant height of cliff---- Use the graphical method

to convert height difference and temperature difference to calculate that for every 1000m increase in altitude, the temperature decreases by 6°C

(5), make a terrain profile

A , Find all intersection points of line segments and contour lines (note to distinguish rivers and contour lines)

B. Determine the height values ​​of all intersection points and the height range of both endpoints

C , draw the corresponding contour lines in the terrain profile

D. Calculate the size of the vertical scale and horizontal scale

E. Mark all intersection points and sums in the terrain profile End points (pay attention to the density relationship between points)

F. Just connect all the points with smooth curves

(6) Interpretation of terrain type: Chapter 1 Take a look at the notes of the contour lines in one step. Straight contour lines indicate that the terrain below 200 meters may be a plain, and straight contour lines indicate that the terrain above 500 meters may be a plateau; the second step is to look at the shape of the contours (including extension direction, bending direction and closure status) ). If the contour lines are straight, it may be plain terrain or plateau terrain. If the contour line is closed, it may be hills, mountains or basins (contour lines indicate that the terrain is low on the inside and high on the outside as basins or depressions; closed contour lines indicate low on the outside and high on the inside, and the terrain is marked between 200-500 meters The terrain in between is hilly, and the terrain above 500 meters is marked as mountainous). Contour lines that bend upward are valleys, and contour lines that bend downward are ridges. The third step is to look at the density of the contour lines and determine the size and type of the slope. When interpreting the terrain type in the profile, you must look at the profile shape and corresponding altitude. The method can be carried out by referring to the above method.

3. Application in practice

(1) Combined with climate

High altitude and low location. The vertical lapse rate is 0.60C/100m. The basin is not easy to dissipate heat, and the temperature is relatively high, which can easily cause the retention of polluted air. There is more precipitation on the windward slope and less precipitation on the leeward slope. The wind speed is high in the high plains due to the flatter terrain, the wind speed is high in the passes due to the narrow tube effect, and the wind speed is low in the mountain basins. The higher the altitude, the lower the air pressure. The air pressure is proportional to the boiling point. The air pressure at the top of the mountain is low and the boiling point is low.

(2) Combination with vegetation

Sun-loving vegetation is on sunny slopes; shade-loving vegetation is on shady slopes. The distribution of the same vegetation is higher on sunny slopes.

(3) Combined with river hydrology

Rivers may develop in valleys (high altitude in the upper reaches of the river and low altitude in the downstream); rivers are unlikely to develop on the ridges and are often watersheds. Mountainous terrain forms radial water systems; basin terrain forms centripetal water systems; parallel mountainous areas form parallel water systems. Rivers with dense contours have fast flow speeds and abundant water energy; rivers with sparse contours have slow flow speeds and convenient water transportation; the size of the basin area (the connection between the ridges - the catchment area) determines the flow rate. Waterfalls are easy to form on the steep cliffs in the valley

(4), combined with location

Selection of transportation lines: taking advantage of favorable terrain, we must consider both the distance and the The route is stable (spacing, slope, etc.), usually detouring between two contour lines, and distributed along the contour line (extension direction) to reduce the slope. Only when necessary can it cross one or two contour lines. ; When climbing mountains, choose gentle slopes and pass through saddles; pass through rivers as little as possible and build fewer bridges to reduce construction difficulty and investment; avoid passing through alpine areas, permafrost areas, underground caves, cliffs, swamps, etc. Desert areas.

Selection of water diversion lines: Pay attention to diverting water from high places to low places to achieve self-flow, and the lines should be as short as possible, so that economic investment will be less.

Pipeline selection: The line should be as short as possible to save investment; it can pass through rivers and mountains, but the geological conditions must be stable.

Selection of reservoir dam site: Consideration should be given to the reservoir site, dam site and whether resettlement is required after the construction of the reservoir. ①． Choose the outlet in a narrow river or at the outlet of a basin or depression (i.e., a "pocket-shaped" area, where the "small mouth" is conducive to dam construction, and the "big bag" has a broad hinterland and large storage capacity. Because the project volume is small, the project cost is low); ②. Choose a place with good geological conditions and try to avoid faults, karst landforms, etc. to prevent reservoir earthquakes; ③. Consider the situation of land relocation and minimize flooding of farmland and villages. ④ Also note that when building a reservoir, the water source must be sufficient.

Selection of mountainous village address: generally choose a valley location, which requires flat and open terrain, close to water sources, convenient transportation, and facing the sun. The selection of campsites is similar.

Urban layout form and terrain: Plains are suitable for concentrated and compact types; mountainous areas are suitable for dispersed and loose types.

Selection of agricultural types: Based on the terrain type and terrain undulations reflected in the contour topographic map , slope gradient, combined with climate and water source conditions, and propose a reasonable layout plan for agriculture, forestry, animal husbandry and fishery according to local conditions; such as developing farming in plain areas, and developing forestry and animal husbandry in mountainous and hilly areas. If the slope is >25°, it is not suitable to be developed into terraces. The investment will be large but the return will be small, and it will easily cause natural disasters such as soil erosion and landslides.

Determination of industrial location: Analyze from many aspects. Factories and mines that pollute the environment should be located downstream of rivers and below the dominant wind direction all year round. Combined with geological and terrain conditions, they should be placed on a solid foundation and at the same height. Flat and open areas with large line spacing; if electronics, semiconductor, photosensitive equipment factories, etc. need to be built in locations with clean air and beautiful environment, from the perspective of economic benefits, they should be as close as possible to the sources of raw materials, fuels, water sources and other resources.

The construction of the port should consider choosing a sheltered deep-water bay (with dense contours); avoid rivers with high sand content (sparse contours - slow flow) to avoid channel siltation. Airports are mostly located in open areas with moderate slopes.

The weather station should be built in a location with moderate terrain slope and open terrain. The sanatorium should be built in a place with gentle slope, pleasant climate and fresh air. The salt pans are located on the coastal flats of the plain.

(2) Isotherm lines

Interpretation method

1. Analyze the trend (extension direction): Parallel to the latitude line, that is, east-west trend - latitude factor or solar radiation; Parallel to the coastline - the nature of the sea and land or the distribution of sea and land; Parallel to the contour line or the trend of the mountains - topographic factors.

2. Analyze the bending situation: horizontal line method - compare the temperature at the bend and the intersection; convex value method - convex high (convex to the high value area) is low (low value), convex low (convex to the low value area) is high (high value).

3. Analyze the sparse and dense conditions: sparse - small temperature difference - my country's July temperature, tropical areas, oceans, mountain steep slopes, and fronts; dense - large temperature difference - my country's January temperature, temperate areas, land, and mountain gentle slopes.

4. Analyze numerical characteristics: large and small, moving in the middle; closed curves are large or small; high value areas - continents in summer, oceans in winter, warm currents flowing through, low terrain (valleys, basins or depressions), cities; low value areas - winter Continent, summer ocean, cold currents flowing through, high terrain (mountains, ridges).

College entrance examination ability requirements:

1. Determine the position of the southern and northern hemispheres: the degree of the isotherm gradually decreases from north to south or the degree of the isotherm gradually increases from south to north. Southern Hemisphere. The northern hemisphere is the area where the degree of isotherms gradually increases from north to south or the degree of isotherms gradually decreases from south to north.

2. Determine the location of land and ocean: the isotherms on land in winter bend toward low latitudes (meaning that the land in winter is cooler than the ocean at the same latitude), and the isotherms on the ocean bend toward high latitudes (meaning that The ocean is warmer in winter than the land at the same latitude). The isotherms on land in summer bend toward high latitudes (meaning that the land in summer is warmer than the ocean at the same latitude), and the isotherms on the ocean bend toward low latitudes (meaning that the ocean in summer is cooler than the land at the same latitude).

3. Determine the month (January or July): When judging the month, pay attention to the differences between winter and summer seasons in the southern and northern hemispheres.

January: The isotherms on land in the Northern Hemisphere bend to the south, and the isotherms on the oceans bend to the north; in the Southern Hemisphere, the isotherms on land bend to the south, and the isotherms on the oceans bend to the north.

July: The isotherms on land in the Northern Hemisphere bend to the north, and the isotherms on the oceans bend to the south; in the Southern Hemisphere, the isotherms on land bend to the north, and the isotherms on the oceans bend to the south.

4. Determine cold and warm currents: The direction of ocean currents is consistent with the protruding direction of the isotherm. The water temperature in the center of the cold current is lower than that in other areas at the same latitude, so the isotherm curves toward lower latitudes. The water temperature in the center of the warm current is higher than that in other areas at the same latitude, so the isotherm curves toward high latitudes.

5. Determine the high and low relief of the terrain: where the isotherms on the land protrude towards low latitudes, it indicates that the terrain there has increased; where the isotherms protrude towards high latitudes, it indicates that the terrain The terrain is lowered. On the closed isotherm map, the value of the mountain isotherm is smaller toward the center; the value of the basin isotherm is larger.

6. Determine the size of the temperature difference: Under normal circumstances, regardless of time and space, the isotherms are dense and the temperature difference is large. On the contrary, the temperature difference is small. It can be seen from the temperature distribution characteristics of the world and my country: ① The isotherms are dense in winter and sparse in summer. Because the temperature difference between different places is larger in winter than in summer. ②The isotherms are dense in the temperate zone and sparse in the tropical zone.

Because the temperature difference in temperate areas is greater than that in tropical areas with high temperatures all year round. ③The land isotherms are dense and the ocean isotherms are thin. Because the surface shape of the land is complex and the heat capacity of the ocean is large, the temperature difference on the land is greater than that on the sea surface. ④The isotherms on steep slopes in mountains are dense, while the isotherms on gentle slopes in mountains are sparse. ⑤The isotherms at the front are dense.

Analyze the influencing factors of temperature

The main influencing factors of temperature are: (1), latitude factors (2), sea and land factors (3), terrain factors (4), and ocean current factors Iso

——If the isotherm is roughly parallel to the latitude and runs east-west, the dominant factor is the latitude factor

——If the isotherm curves near the coast and is roughly parallel to the coastline, If it runs north-south, the dominant factor is sea and land factors

-On land, the isotherms bend, usually as a result of topographic factors.

The temperature in the valley is higher than on both sides: the isotherm convex from high temperature to low temperature. Such as the Wei River Valley, Fen River Valley, Yarlung Zangbo River Valley, etc.

The temperature in the mountains is lower than that on the two sides: the isotherms convex from low temperature to high temperature. Such as Daxinganling, Changbai Mountain, Taihang Mountain, Wuyi Mountain, etc.

The temperature on the leeward slopes of mountains increases due to the foehn effect: the isotherms convex from high temperature to low temperatures

Mountain (hills, mounds) terrain: the isotherms are closed, low in the middle and high around the sides

Basin (valley, depression) terrain: closed isotherms, high in the middle and low on all sides

——On the ocean, the isotherms bend, usually as a result of ocean current factors.

The temperature where the cold current flows is lower than on both sides: the isotherm bulges from low temperature to high temperature.

The temperature where the warm current flows is higher than on both sides: the isotherm convex from high temperature to low temperature. (The flow direction of the ocean current is always consistent with the convex direction of the isotherm)

(4). Horizontal isobars

1. Determine the air pressure system

High pressure center: The air pressure is high in the center and low around it

Low pressure center: The air pressure is low in the center and high around it

High pressure ridge: high pressure bulges toward low pressure

Low pressure trough: low pressure bulges toward high pressure

Saddle-shaped area: high pressure on both sides, low pressure on both sides, symmetrical distribution

2. Determine weather phenomena

Subsidence prevails near the center of the high-pressure system The air flow is sunny

The prevailing updraft center is cloudy and rainy near the center of the low-pressure system

The weather is sunny near the high-pressure ridge

The weather is cloudy and rainy near the low-pressure trough

3. Determine the direction of the wind

Determine the wind direction: first apply the horizontal air pressure gradient force, and then determine the wind direction.

Interpretation of wind direction: Wind direction refers to the direction of the wind.

(1). The wind direction at high altitude is parallel to the isobars

(2) The wind direction near the ground is oblique to the isobars

< p>(3), the wind direction of typhoon (cyclone system) - it is necessary to focus on mastering (not only static mastering, but also dynamic mastering)

Typhoons blow northeasterly in the north, southwesterly in the south, and southeasterly in the east Wind, northwest wind blows from the west

Easterly wind blows from the northeast, southerly wind blows from the southeast, westerly wind blows from the southwest, and northerly wind blows from the northwest

(4), subtropical high (inverse wind) Cyclone system) wind direction

4. Determine the wind strength

(1) On the same isobars map, the denser the isobars, the greater the wind; the sparser the isobars. , the smaller the wind.

(2) On different isobars, the magnitude of the wind force is proportional to the density of the isobars (proportional), the size of the scale (proportional), and the size of the isobars (proportional). ) is related. ----Use the calculation method (the same as the method for judging the steepness and gentleness of the slope)

5. Determine the seasonal month

January is the month when the high pressure on the Eurasian continent or the North American continent is strong. Winter and southern summer

The Eurasian or North American continent has strong low pressure in July, northern summer and southern winter

(18), population density contours

Analyze the laws of population distribution in a certain area and the natural, historical, social, and economic factors that affect it by interpreting population density contours.