- limited to the surface of the land or the bottom of the oceans. It also has a geophysical boundary, which is the section Moho. The boundary is characterized by the fact that seismic wave velocities sharply increase here. It was installed in $1909 by a Croatian scientist A. Mohorovic ($1857$-$1936$).
The earth's crust is made up sedimentary, igneous and metamorphic rocks, and in terms of composition it stands out three layers. Rocks of sedimentary origin, the destroyed material of which was redeposited in the lower layers and formed sedimentary layer the earth's crust, covers the entire surface of the planet. In some places it is very thin and may be interrupted. In other places, it reaches a thickness of several kilometers. Sedimentary are clay, limestone, chalk, sandstone, etc. They are formed by sedimentation of substances in water and on land, they usually lie in layers. From sedimentary rocks, you can learn about the natural conditions that existed on the planet, so geologists call them pages of the history of the Earth. Sedimentary rocks are subdivided into organogenic, which are formed by the accumulation of the remains of animals and plants and non-organogenic, which are further subdivided into clastic and chemogenic.
clastic rocks are the product of weathering, and chemogenic- the result of the precipitation of substances dissolved in the water of the seas and lakes.
Igneous rocks make up granite layer of the earth's crust. These rocks were formed as a result of solidification of molten magma. On the continents, the thickness of this layer is $15$-$20$ km, it is completely absent or very much reduced under the oceans.
Igneous matter, but poor in silica composes basaltic layer with a high specific gravity. This layer is well developed at the base of the earth's crust of all regions of the planet.
The vertical structure and thickness of the earth's crust are different, therefore, several types of it are distinguished. According to a simple classification, there is oceanic and continental Earth's crust.
continental crust
Continental or continental crust is different from oceanic crust thickness and device. The continental crust is located under the continents, but its edge does not coincide with the coastline. From the point of view of geology, the real continent is the entire area of the continuous continental crust. Then it turns out that the geological continents are larger than the geographical continents. Coastal areas of the continents, called shelf- these are parts of the continents temporarily flooded by the sea. Such seas as the White, East Siberian, Azov Seas are located on the continental shelf.
There are three layers in the continental crust:
- The upper layer is sedimentary;
- The middle layer is granite;
- The bottom layer is basalt.
Under young mountains this type of crust has a thickness of $75$ km, under plains up to $45$ km, and under island arcs up to $25$ km. The upper sedimentary layer of the continental crust is formed by clay deposits and carbonates of shallow marine basins and coarse clastic facies in foredeeps, as well as on the passive margins of Atlantic-type continents.
Magma invading the cracks in the earth's crust formed granite layer which contains silica, aluminum and other minerals. The thickness of the granite layer can be up to $25$ km. This layer is very ancient and has a solid age of $3 billion years. Between the granite and basalt layers, at a depth of up to $20$ km, there is a boundary Conrad. It is characterized by the fact that the propagation velocity of longitudinal seismic waves here increases by $0.5$ km/sec.
Formation basalt layer occurred as a result of outpouring of basalt lavas onto the land surface in zones of intraplate magmatism. Basalts contain more iron, magnesium and calcium, so they are heavier than granite. Within this layer, the propagation velocity of longitudinal seismic waves is from $6.5$-$7.3$ km/sec. Where the boundary becomes blurred, the velocity of longitudinal seismic waves increases gradually.
Remark 2
The total mass of the earth's crust of the mass of the entire planet is only $0.473$%.
One of the first tasks associated with determining the composition upper continental bark, young science undertook to solve geochemistry. Since the bark is made up of a wide variety of rocks, this task was very difficult. Even in one geological body, the composition of rocks can vary greatly, and different types of rocks can be common in different areas. Based on this, the task was to determine the general, average composition that part of the earth's crust that comes to the surface on the continents. This first estimate of the composition of the upper crust was made by Clark. He worked as an employee of the US Geological Survey and was engaged in the chemical analysis of rocks. In the course of many years of analytical work, he managed to summarize the results and calculate the average composition of the rocks, which was close to to granite. Job Clark was subjected to harsh criticism and had opponents.
The second attempt to determine the average composition of the earth's crust was made by W. Goldschmidt. He suggested that moving along the continental crust glacier, can scrape and mix exposed rocks that would be deposited during glacial erosion. They will then reflect the composition of the middle continental crust. Having analyzed the composition of banded clays, which were deposited during the last glaciation in Baltic Sea, he got a result close to the result Clark. Different methods gave the same scores. Geochemical methods were confirmed. These issues have been addressed, and the assessments received wide recognition. Vinogradov, Yaroshevsky, Ronov and others.
oceanic crust
oceanic crust located where the depth of the sea is more than $ 4 $ km, which means that it does not occupy the entire space of the oceans. The rest of the area is covered with bark intermediate type. The oceanic-type crust is not organized in the same way as the continental crust, although it is also divided into layers. It has almost no granite layer, while the sedimentary one is very thin and has a thickness of less than $1$ km. The second layer is still unknown, so it is simply called second layer. Bottom third layer basaltic. The basalt layers of the continental and oceanic crust are similar in seismic wave velocities. The basalt layer in the oceanic crust prevails. According to the theory of plate tectonics, the oceanic crust is constantly formed in the mid-ocean ridges, then it moves away from them and in areas subduction absorbed into the mantle. This indicates that the oceanic crust is relatively young. The largest number of subduction zones is typical for Pacific Ocean where powerful seaquakes are associated with them.
Definition 1
Subduction- this is the lowering of rock from the edge of one tectonic plate into a semi-molten asthenosphere
In the case when the upper plate is a continental plate, and the lower one is an oceanic one, ocean trenches.
Its thickness in different geographical areas varies from $5$-$7$ km. Over time, the thickness of the oceanic crust practically does not change. This is due to the amount of melt released from the mantle in the mid-ocean ridges and the thickness of the sedimentary layer at the bottom of the oceans and seas.
Sedimentary layer oceanic crust is small and rarely exceeds a thickness of $0.5$ km. It consists of sand, deposits of animal remains and precipitated minerals. Carbonate rocks of the lower part are not found at great depths, and at a depth of more than $4.5$ km, carbonate rocks are replaced by red deep-water clays and siliceous silts.
Basalt lavas of tholeiite composition formed in the upper part basalt layer, and below lies dike complex.
Definition 2
dikes- these are channels through which basalt lava flows to the surface
Basalt layer in zones subduction turns into ecgoliths, which submerge in depth because they have a high density of surrounding mantle rocks. Their mass is about $7$% of the mass of the entire Earth's mantle. Within the basalt layer, the velocity of longitudinal seismic waves is $6.5$-$7$ km/sec.
The average age of the oceanic crust is $100$ million years, while its oldest sections are $156$ million years old and are located in the basin Pijafeta in the Pacific Ocean. The oceanic crust is concentrated not only within the bed of the World Ocean, it can also be in closed basins, for example, the northern basin of the Caspian Sea. Oceanic the earth's crust has a total area of $306$ million sq. km.
Lesson topic: "The structure of the earth's crust. Earthquakes.
The purpose and objectives of the lesson:
Tutorial: to form the concepts: "types of the earth's crust", "earthquakes", "movement of the earth's crust".
Educational : continue to develop skills in working with diagrams and drawings.
Nurturing: to promote the formation of students' interest in the study of the lithosphere.
Lesson type : learning new material
Equipment : projector, computer, physical map of Russia.
Stage of the lesson, slides
teacher actions. Forms of organizing the work of a teacher
Student actions. Forms of organizing the work of children
1. Organizational and motivational stage of the lesson
Determining the topic of the lesson
Formulation
lesson objectives
The teacher asks you to answer the following questions:
1. On the surface, which inner shell of the Earth do we live in?
2. How is the Earth's crust different from the mantle?
3. What do you know about the earthquake?
4. Where can they occur?
What do you think we are going to learn in today's lesson?
Make assumptions about the topic of the lesson, plan their actions in the lesson
Define tasks with the help of the teacher.
Formulate 1 task: Study the structure of the earth's crust.
Formulate 2 tasks: What are the causes of earthquakes?
Formulate 3 tasks: How and where are tsunamis formed, why are they dangerous?
Personal UUD:
formation of educational and cognitive motivation and interest in learning.
Cognitive UUD:
independent selection and formulation of a cognitive goal.
Communicative UUD:
Regulatory UUD: accept and maintain the educational goal and objectives, goal setting - setting the educational goal and objectives; with the help of the teacher, they determine what needs to be learned in the lesson, planning - drawing up a plan and sequence of actions.
Creating a motivational set
Why is it necessary for a person to study the structure and movement of the earth's crust?
Students give their guesses
Cognitive UUD:
formation of a linguistic guess.
Regulatory UUD:
self-control.
2.Procedurally - meaningful stage of the lesson
1 Earth's crust.
Textbook st.46 fig.25 Pathfinder's diary st.24
Cognitive UUD:
Communicative UUD: listen to the interlocutor, build clear statements for the interlocutor.
Regulatory UUD: to independently assess the correctness of the performance of actions, make the necessary adjustments; the ability to independently acquire new knowledge and practical skills.
2. Violation of the layers of the earth's crust.
The teacher's story about the movement of the earth's crust. (fig. 26 tutorial)
Movement of the earth's crust
vertical horizontal
textbook 47 (dams) horst, graben
folding-folding process
Fold area- a section of the earth's crust, within which layers of rocks are crumpled into folds.
Diary - pathfinder st.24-25 ass. 2
video: "The formation of folded and blocky mountains."
Cognitive UUD: perceive information by ear.
Communicative UUD: listen to the interlocutor, build clear statements for the interlocutor.
Regulatory UUD:
3. Earthquakes
Teacher's story (outline)
earthquakes- tremors and vibrations in the earth's crust.
earthquake source- a place at a depth where the impact occurred, a rupture and displacement of rocks is formed.
Earthquake epicenter- a place on the earth's surface located above the hearth.
Tsunamis are giant waves.
Diary - Pathfinder Art.25 Assignment 3
video : "Earthquakes"
Work in the pathfinder's diary.
Cognitive UUD: perceive information by ear.
Communicative UUD: listen to the interlocutor, build clear statements for the interlocutor.
Regulatory UUD: to independently assess the correctness of the performance of actions, make the necessary adjustments; ability to independently acquire new knowledge and practical skills
4. The intensity of the earthquake.
Teacher's story. Rice. 31v textbook art. 49, Art. 51 tables.
Seismology- the science of the origin of seismic waves.
Seismograph- a device for recording seismic waves.
Cognitive UUD: perceive information by ear.
Communicative UUD: listen to the interlocutor, build clear statements for the interlocutor.
3. Stage of fixing
5. Fixing
Questions:
1.
I was born in the ocean
From an earth tremor.
And I run towards you
Destroy everything for sure!
(tsunami)
2. The place where the depths of the Earth begin to break, and the strongest shocks are concentrated. (epicenter)
3. A device that records the movement of the soil during earthquakes.
4. The place where an underground shock occurs. (hearth)
5. Name the movement of the earth's crust.
6. Name the types of the earth's crust.
7. Seismology.
8.Seismograph.
9. Tsunami.
Cognitive UUD: perceive information by ear.
Communicative UUD: listen to the interlocutor, build clear statements for the interlocutor.
4. Reflective stage of the lesson
5. Reflection
Reception "Finish the phrase"
What did I learn in class...
Evaluate and express their attitude to the work in the lesson in verbal form.
D.z.
P.9
D.p. Find out if there were earthquakes in your area. Major earthquakes in the world.
Subject: The structure of the earth's crust
The purpose of the lesson:
1) To form knowledge about lithospheric plates and their movements, geological chronology and geochronological table.
2) Develop the ability to work with thematic maps.
3) Raise interest in the subject of geography.
Teaching method: verbal
Form of organization: collective
Lesson type: combined
Type of lesson: problem learning
Equipment: physical map of the world, map of the structure of the earth's crust
I. Organizing time. Greetings. Identification of absentees.
II. Checking homework.
1. Cartographic projections (map - a reduced, generalized image of the globe using conventional signs based on mathematical laws - on a certain scale and projection; cartographic projections; classify distortions of length, areas, shapes and angles;
Projections - equiangular, equal and arbitrary; in equiangular, angles and shapes are preserved, lengths and areas are distorted; equal-area projections - areas are accurate, and angles and shapes are distorted; arbitrary projections - all kinds of distortions, but evenly distributed - there are less distortions in the center than at the edges;
Classification by types of transfer to the surface: cylindrical - little distortion at the equator, a lot at the poles, conical - the regions of the poles are distorted, polyconical - used for world maps, the center is distorted; azimuth are used to image the polar region)
2. A system of conventional signs (scale or contour - the dimensions of objects; off-scale conventional signs - geometric shapes, drawings, letters - settlements, minerals, drawings of animals and plants; linear - rivers, roads, communication lines, borders; explanatory and describing signs - the length of the rivers, the height of the mountain, the depth of the depression)
3. Grouping of maps (by territorial coverage, by scale, by content; by purpose; topographic maps - large-scale; complex ones show several components and their relationship)
4. Geographical dictation
1. Part of the earth's surface that is visible to us is visible around us at an open level of space (horizon).
2. The physical map of the world in terms of coverage of the territory belongs to the group (world maps).
3. The boundary of the troposphere above the equator is located at an altitude (18 km).
4. Most of the air in the (troposphere).
5. Temperate climate, coniferous trees, large predators and artiodactyls - signs that characterize (taiga).
6. The position of natural zones is determined (by the ratio of heat and moisture).
III. Exploring a new topic.
Write the topic of the lesson on the board and explain the objectives of the lesson.
1. What is the internal structure of the Earth?
2. What shells does it consist of?
3. What is the lithosphere?
4. What rocks do you know?
5. Problematic question: Is the thickness of the earth's crust the same everywhere? Where do earthquakes most often occur? Why?
1. Continental and oceanic crust (the age of the Earth is 4.5 - 5 billion years; first, the oceanic crust was formed, the oceanic crust - 5-10 km, the continental - 35-80 km).
There are two main types of earth's crust: oceanic and continental. There is also a transitional type of the earth's crust.
Oceanic crust. The thickness of the oceanic crust in the modern geological epoch ranges from 5 to 10 km. It consists of the following three layers:
1) the upper thin layer of marine sediments (thickness is not more than 1 km);
2) middle basalt layer (thickness from 1.0 to 2.5 km);
3) the lower layer of gabbro (thickness is about 5 km).
Continental (continental) crust. The continental crust has a more complex structure and greater thickness than the oceanic crust. Its average capacity is 35-45 km, and in mountainous countries it increases to 70 km. It also consists of three layers, but differs significantly from the ocean:
1) the lower layer composed of basalts (about 20 km thick);
2) the middle layer occupies the main thickness of the continental crust and is conditionally called granite. It is composed mainly of granites and gneisses. This layer does not extend under the oceans;
3) the upper layer is sedimentary. Its average thickness is about 3 km.
In some areas, the thickness of precipitation reaches 10 km (for example, in the Caspian lowland). In some regions of the Earth, the sedimentary layer is absent altogether and a granite layer comes to the surface. Such areas are called shields (eg Ukrainian Shield, Baltic Shield).
On the continents, as a result of the weathering of rocks, a geological formation is formed, called the weathering crust.
The granite layer is separated from the basalt layer by the Konrad surface, on which the speed of seismic waves increases from 6.4 to 7.6 km/sec.
The boundary between the earth's crust and the mantle (both on the continents and on the oceans) runs along the Mohorovichic surface (Moho line). The speed of seismic waves on it jumps up to 8 km / h.
In addition to the two main types - oceanic and continental - there are also areas of a mixed (transitional) type.
On continental shoals or shelves, the crust has a thickness of about 25 km and is generally similar to the continental crust. However, a layer of basalt may fall out in it. In East Asia, in the area of island arcs (the Kuril Islands, the Aleutian Islands, the Japanese Islands, and others), the earth's crust is of a transitional type. Finally, the earth's crust of the mid-ocean ridges is very complex and still little studied. There is no Moho boundary here, and the material of the mantle rises along faults into the crust and even to its surface.
The concept of "earth's crust" should be distinguished from the concept of "lithosphere". The concept of "lithosphere" is broader than "the earth's crust". In the lithosphere, modern science includes not only the earth's crust, but also the uppermost mantle to the asthenosphere, that is, to a depth of about 100 km.
2. Geological chronology and geochronological tables A(the earth's crust was formed about 2.5 billion years; an era is a period of geological time during which significant changes in the earth's crust and living organisms occur)
Of great importance for geographical science is the ability to determine the age of the Earth and the earth's crust, as well as the time of significant events that occurred in the history of their development. The history of the development of the planet Earth is divided into two stages: planetary and geological.
The planetary stage covers the period of time from the birth of the Earth as a planet to the formation of the earth's crust. The scientific hypothesis about the formation of the Earth (as a cosmic body) appeared on the basis of general views on the origin of other planets that make up the solar system. The fact that the Earth is one of the 9 planets of the solar system, you know from the 6th grade course. Planet Earth was formed 4.5-4.6 billion years ago. This stage ended with the appearance of the primary lithosphere, atmosphere and hydrosphere (3.7-3.8 billion years ago).
From the moment the first rudiments of the earth's crust appeared, a geological stage began, which continues to the present. During this period, various rocks were formed. The earth's crust has repeatedly been subjected to slow ups and downs under the influence of internal forces. During the period of subsidence, the territory was flooded with water and sedimentary rocks (sands, clays, etc.) were deposited at the bottom, and during periods of sea rise, they receded and a plain formed by these sedimentary rocks arose in their place.
Thus, the original structure of the earth's crust began to change. This process continued uninterrupted. At the bottom of the seas and depressions of the continents, a sedimentary layer of rocks accumulated, among which one could find the remains of plants and animals. Each geological period corresponds to their separate types, because the organic world is in constant development.
Determination of the age of rocks. In order to determine the age of the Earth and present the history of its geological development, methods of relative and absolute chronology (geochronology) are used.
To determine the relative age of rocks, it is necessary to know the patterns of successive occurrence of layers of sedimentary rocks of different composition. Their essence is as follows: if the layers of sedimentary rocks lie in an undisturbed state as they were deposited one by one on the bottom of the seas, then this means that the layer lying below was deposited earlier, and the layer lying above was formed later, therefore he is younger.
Indeed, if there is no lower layer, then it is clear that the upper layer covering it cannot be formed, therefore, the lower the sedimentary layer is located, the greater its age. The topmost layer is considered the youngest.
In determining the relative age of rocks, the study of the successive occurrence of sedimentary rocks of different compositions and the fossilized remains of animal and plant organisms contained in them is of great importance. As a result of the painstaking work of scientists to determine the geological age of rocks and the time of development of plant and animal organisms, a geochronological table was compiled. It was approved at the II International Geological Congress in 1881 in Bologna. It is based on the stages of life development identified by paleontology. This table-scale is constantly being improved.
The units of the scale are eras, divided into periods which are subdivided into eras. The five largest of these divisions - eras - bear names associated with the nature of the life that existed then. For example, the Archean is the time of earlier life, the Proterozoic is the era of primary life, the Paleozoic is the era of ancient life, the Mesozoic is the era of middle life, and the Cenozoic is the era of new life.
Eras are subdivided into shorter periods of time - periods. Their names are different. Some of them come from the names of rocks that are most characteristic of this time (for example, the Carboniferous period in the Paleozoic and the Mole period in the Mesozoic). Most of the periods are named after those localities in which the deposits of a particular period are most fully developed and where these deposits were first characterized. The oldest period of the Paleozoic - the Cambrian - got its name from Cambria - an ancient state in the west of England. The names of the following periods of the Paleozoic - Ordovician and Silurian - come from the names of the ancient tribes of the Ordovicians and Silurians, who inhabited the territory of present-day Wales.
To distinguish between the systems of the geochronological table, conventional signs are adopted. Geological eras are indicated by indices (signs) - the initial letters of their Latin names (for example, Archaean - AR), and period indices - by the first letter of their Latin names (for example, Permian - P).
The determination of the absolute age of rocks began at the beginning of the 20th century, after scientists discovered the law of decay of radioactive elements. In the bowels of the Earth are radioactive elements, such as uranium. Over time, it slowly, at a constant rate, decays into helium and lead. The helium dissipates, while the lead remains in the rock. Knowing the decay rate of uranium (out of 100 g of uranium, 1 g of lead is released within 74 million years), by the amount of lead contained in the rock, one can calculate how many years ago it was formed.
The use of radiometric methods made it possible to determine the age of many rocks that make up the earth's crust. Thanks to these studies, it was possible to establish the geological and planetary age of the Earth. Based on the relative and absolute methods of reckoning, a geochronological table was compiled.
3. Lithospheric plates and their movement (The theory of lithospheric plates was formulated at the beginning of the 20th century by the German scientist A. Wegener.
There are 7 large and dozens of small plates; continental and oceanic plates; rifts - a set of deep faults in the earth's crust, they are the boundary of the divergence of lithospheric plates and areas of the formation of the oceanic earth's crust; the areas of contact between continental and oceanic plates are called the boundary of the collision of lithospheric plates; plates can move at a speed of 5 to 10 cm per year; platforms - relatively flat and stable areas of the earth's crust; ancient - East European, Siberian, Arabian, North American, Australian; shield - outcrop of crystalline rocks that form the basis of ancient platforms - Canadian, Baltic, Aldan; young platforms - West European, West Siberian, Turan, etc.; plate - sections of platforms covered with a layer of sedimentary rocks)
4. Geosynclines (mobile belts of the earth's crust, over 800 active volcanoes on Earth)
A geosyncline is a vast, mobile, permeable area of the earth's crust, where thick sedimentary and volcanogenic rocks initially accumulated, which were then crushed into folds, intruded by rocks of different composition, metamorphosed, brought to the day surface with the formation of mountain folded structures. The inception, development of the geosyncline and its transformation into a mountainous area are explained by decompaction as a result of heating of the mantle matter and the rise of mantle plumes.
The largest, global extent sections of the earth's crust of a geosynclinal structure are called geosynclinal (mobile) belts; subordinate large subdivisions - geosynclinal areas. The smaller areas included in their composition, which differ in some features of their composition and structure, represent the geosynclines proper. The geosynclinal belt is a mobile and permeable element of the lithosphere, which is characterized by a set of certain formations, a regular direction of magmatic phenomena, intense dislocation and metamorphism of sediments and volcanic rocks. In the modern sense, the geosynclinal belt is one of the types of mobile belts of the Earth that occurs at the boundaries of large lithospheric plates (oceanic and continental) or within them.
Within the belt, sedimentary and volcanic strata are intensively accumulated in marine, often deep-water, then island-arc and shallow-water conditions. The mobile belt experiences intense tectonic deformations, regional metamorphism and granitization with transformation into fold-thrust structures with thick continental crust, separated by intermontane and bordered by piedmont troughs. The processes of uplift of the earth's crust, the introduction of large masses of acidic intrusions are most pronounced in the central part of the geosyncline, which G. Shtiele called the eugeosyncline. Along its edges, there are miogeosynclines containing much less effusive strata, as well as intrusions, and generally composed of younger rocks.
There are two stages in the development of the geosyncline: the geosynclinal proper and the orogenic. The first includes two stages - the initial subsidence and preorogenic, the second - early orogenic and proper orogenic.
As a result of erosion, a mountainous country is destroyed, its territory is leveled, and it turns into a platform - an inactive, rigid, leveled area, where the amplitudes of vertical movements and the thickness of precipitation are small. The rocks on the platforms are not metamorphosed, usually occur horizontally, and the igneous formations are represented by basalts. Thus, platforms are stable, rigid sections of the earth's crust of continents with a two-story structure. The lower floor is composed of crystalline rocks, the upper - sedimentary.
V. Consolidation of the studied topic.
1. The Cenozoic era is divided into 3 main periods (Paleogene, Neogene, Quaternary)
2. The Earth's crust is the thickest (in the Himalayas)
3. Most often, volcanic eruptions, earthquakes, hot springs are formed (in mountainous areas, on the outskirts of the continents)
4. What are the stages of the geological history of the development of the Earth?
5. What stage of the Earth's development is geological?
6. How is the age of rocks determined?
7. Compare the duration of geological eras and periods according to the geochronological table.
VI. Homework. Know the structure of the earth's crust, learn definitions. Review what you have learned from the textbook.
VII. Summary of the lesson.
Lithosphere. Earth's crust. 4.5 billion years ago, the Earth was a ball consisting of some gases. Gradually, heavy metals such as iron and nickel sank to the center and condensed. Light rocks and minerals floated to the surface, cooled and hardened.
The internal structure of the Earth.
It is customary to divide the body of the Earth into three main parts - lithosphere(earth crust) mantle And core.
The core is the center of the earth , the average radius of which is about 3500 km (16.2% of the volume of the Earth). As suggested, it consists of iron with an admixture of silicon and nickel. The outer part of the core is in a molten state (5000 °C), the inner, apparently, is solid (subnucleus). The movement of matter in the core creates a magnetic field on Earth that protects the planet from cosmic radiation.
The core is changing mantle , which extends almost 3000 km (83% of the Earth's volume). It is believed that it is solid, at the same time plastic and red-hot. The mantle is made up of three layers: Golitsyn layer, Gutenberg layer and substrate. The upper part of the mantle, called magma , contains a layer with reduced viscosity, density and hardness - the asthenosphere, on which sections of the earth's surface are balanced. The boundary between the mantle and the core is called the Gutenberg layer.
Lithosphere
Lithosphere - the upper shell of the "solid" Earth, including the earth's crust and the upper part of the underlying upper mantle of the Earth.
Earth's crust - the upper shell of the "solid" Earth. The thickness of the earth's crust is from 5 km (under the oceans) to 75 km (under the continents). The earth's crust is heterogeneous. It distinguishes 3 layers – sedimentary, granite, basalt. The granite and basalt layers are so named because they contain rocks similar in physical properties to granite and basalt.
Compound the earth's crust: oxygen (49%), silicon (26%), aluminum (7%), iron (5%), calcium (4%); the most common minerals are feldspar and quartz. The boundary between the earth's crust and mantle is called moho surface .
Distinguish continental And oceanic earth's crust. Oceanic different from the continental (mainland) lack of granite layer and much lower power (from 5 to 10 km). Thickness continental crust on the plains 35-45 km, in the mountains 70-80 km. On the border of the continents and oceans, in the areas of the islands, the thickness of the earth's crust is 15-30 km, the granite layer is wedged out.
The position of the layers in the continental crust indicates different time of its formation . The basalt layer is the oldest, younger than it is granite, and the youngest is the upper, sedimentary, developing at the present time. Each layer of the crust was formed over a long period of geological time.
Lithospheric plates
The earth's crust is in constant motion. The first hypothesis about continental drift(i.e. the horizontal movement of the earth's crust) put forward at the beginning of the twentieth century A. Wegener. On its basis, created theory of lithospheric plates . According to this theory, the lithosphere is not a monolith, but consists of seven large and several smaller plates "floating" on the asthenosphere. The boundary regions between lithospheric plates are called seismic belts - these are the most "restless" areas of the planet.
The earth's crust is divided into stable and mobile sections.
Stable areas of the earth's crust - platforms- are formed at the site of geosynclines that have lost their mobility. The platform consists of a crystalline basement and a sedimentary cover. Depending on the age of the foundation, ancient (Precambrian) and young (Paleozoic, Mesozoic) platforms are distinguished. Ancient platforms lie at the base of all continents.
Mobile, highly dissected parts of the earth's surface are called geosynclines ( folded areas ). In their development, there are two stages : at the first stage, the earth's crust experiences subsidence, sedimentary rocks accumulate and metamorphize. Then the uplift of the earth's crust begins, the rocks are crushed into folds. There were several epochs of intensive mountain building on Earth: Baikal, Caledonian, Hercynian, Mesozoic, Cenozoic. In accordance with this, different areas of folding are distinguished.
The distribution and age of platforms and geosynclines is shown in tectonic map (map of the structure of the earth's crust).
Summary of the lesson “Lithosphere. Earth's crust". Next topic .
Earth structure
The lithosphere is a solid shell of the Earth, including the earth's crust and the upper part of the mantle. The lithosphere plays a big role in human life, because this is the territory where people live, they build houses and various structures, use the bowels of the Earth, extracting various minerals that are used in many sectors of the national economy and improving human well-being
The earth has a layered structure.
There are three major layers:
1. Earth's crust.
2. Mantle.
As we move deeper into the Earth, temperature and pressure increase. In the center of the Earth is the core, its radius is about 3500 km, and the temperature is more than 4500 degrees. The core is surrounded by a mantle, its thickness is about 2900 km. Above the mantle is the earth's crust, its thickness varies from 5 km (under the oceans) to 70 km (under the mountain systems). The earth's crust is the hardest shell. The substance of the mantle is in a special plastic state; this substance can slowly flow under pressure.
Rice. 1. The internal structure of the Earth
Earth's crust
Earth's crust- the upper part of the lithosphere, the outer solid shell of the Earth.
The earth's crust is made up of rocks and minerals.
Rice. 2. The structure of the Earth and the earth's crust
There are two types of earth's crust:
1. Continental (it consists of sedimentary, granite and basalt layers).
2. Oceanic (it consists of sedimentary and basalt layers).
Rice. 3. The structure of the earth's crust
Mantle
The mantle accounts for 67% of the total mass of the Earth and 87% of its volume. Separate the upper and lower mantle. The material of the mantle can move under pressure. Internal heat from the mantle is transferred to the earth's crust.
Core
The core is the deepest part of the Earth. There is an outer liquid core and an inner solid core.
Properties of the earth's crust
Most of the earth's crust is covered by the waters of the oceans and seas. The continental crust is much larger than the oceanic and has three layers. The upper part of the earth's crust is heated by the sun's rays. At a depth of more than 20 meters, the temperature practically does not change, and then increases.
The study of the internal structure of the Earth
The most accessible for human study is the upper part of the earth's crust. Sometimes deep wells are made to study the internal structure of the earth's crust. The deepest well is over 12 km deep. Help to study the earth's crust and mines. In addition, the internal structure of the Earth is studied using special instruments, methods, images from space and sciences: geophysics, geology, seismology.
Bibliography
Main
1. Initial course of geography: Proc. for 6 cells. general education institutions / T.P. Gerasimova, N.P. Neklyukov. – 10th ed., stereotype. – M.: Bustard, 2010. – 176 p.
2. Geography. Grade 6: atlas. – 3rd ed., stereotype. – M.: Bustard, DIK, 2011. – 32 p.
3. Geography. Grade 6: atlas. - 4th ed., stereotype. – M.: Bustard, DIK, 2013. – 32 p.
4. Geography. 6 cells: cont. cards. – M.: DIK, Bustard, 2012. – 16 p.
Encyclopedias, dictionaries, reference books and statistical collections
1. Geography. Modern illustrated encyclopedia / A.P. Gorkin. – M.: Rosmen-Press, 2006. – 624 p.
Materials on the Internet
1. Federal Institute of Pedagogical Measurements ().
2. Russian Geographical Society ().
4. 900 presentations for children and 20,000 presentations for schoolchildren ().
