The research method of earth science is related to the characteristics of its research object, and the earth as its research object mainly has the following characteristics:
Universality and Microscopy of (1) Space
The earth is a huge object, its circumference is greater than 4× 104 km, and its surface area is greater than 5× 108 km2. Therefore, whether it is to study the atmosphere, hydrosphere, biosphere and solid earth, its space is very broad. Such a huge space and object itself are composed of different scales or scales of space and material bodies. Therefore, to study the huge earth, it is necessary to study the space and its material bodies with different scales or scales, especially the microscopic space and material characteristics, such as the chemical composition and chemical element characteristics of its corresponding objects in different disciplines. Geology should study the crystal structure of minerals, hydrooceanography should study the movement of water quality points, and meteorology should study the activity of gas molecules. Moreover, the whole earth system is an open dynamic system, and there is always an exchange of matter and energy between it and the cosmic environment (earth-moon system, solar system, galaxies, etc.). The occurrence, development and evolution of various natural phenomena and processes in the earth system are inseparable from the cosmic environment in which they live. Therefore, modern earth science began to pay full attention to the study of the influence of the cosmic environment on the earth system; That is to say, the spatial scope of the study goes beyond the earth system and involves a broader cosmic environment (Figure 0- 1). Only by combining different scales of research and combining macro and micro can we get a correct and regular understanding.
(2) wholeness (or systematicness) and diversity (or difference and diversity)
The whole earth is an organic whole, which is a unified system composed of subsystems at different levels and closely related; Not only in space, the inner and outer circles of the earth are a continuous whole, but also among the inner and outer circles of the earth, between the inner and outer circles, and between the outer circles. The movement and change of a circle or a part will affect the changes of other parts and even other circles to varying degrees, which fully shows their organic integrity. However, the earth is also an anisotropic body, and its different components (or subsystems) have certain differences in material state, movement and evolution characteristics, showing diversity or pluralism. For example, there are obvious differences in geographical environment and climate environment in different regions, and there are also obvious differences in hydrological conditions in different regions. The difference between the solid earth, especially in different parts of the crust, is more significant, such as continents, oceans, mountains and plains. This difference is not only manifested in the composition of space and matter, but also in their movement, change, formation and development.
(3) the persistence and instantaneity of time
According to scientific calculation, the earth can be traced back to 4.6 billion years. In this long time, many important natural events have taken place on the earth, such as land and sea changes, mountain formation, biological evolution and so on. Most of these events are extremely slow and often take millions or even tens of millions of years to complete. It is difficult for a short life to witness the whole process of these events, only to observe the results left after the completion of the events and a certain stage of the events that are taking place. However, some events can be completed in a short time. For example, weather phenomena often appear in days, hours or even shorter time, and earthquakes and volcanic eruptions also occur in a very short time.
(4) Complexity and orderliness of natural processes.
The evolution of the earth has gone through a complicated process. There are both physical and chemical changes; There is not only the action process under normal temperature and pressure on the surface, but also the action process under high temperature and high pressure in the deep underground. In addition, various natural processes are influenced by regional conditions and have regional differences. Therefore, the natural process is extremely complex, and because of its long and irreversibility, it is difficult to completely reshape and reproduce its process by relying on human strength, thus increasing the arduousness of earth science research. However, these complex natural processes are not chaotic, they all have conditions and processes for their development, and they all have certain laws to follow, which is also an important research task for earth scientists.
The characteristics of the research object determine that there are some unique research methods in earth science, and with the development and progress of science and technology, the research methods in earth science will be continuously supplemented and upgraded. The selected research methods are briefly described as follows:
(1) field investigation
The vastness of space determines that earth scientists should first observe nature in the wild and study it as a natural laboratory, but it is impossible to move huge and complex nature indoors for study. Field investigation is the most basic and important link in earth science work, and it can obtain the first-hand information of the research object. Such as field geological survey, water system and hydrological survey, physical geography survey, soil survey, resources and environment survey, etc. Only by going to the site to collect the original data carefully can we provide the possibility for solving the earth science problems correctly.
(2) Instrument observation
Instrumental observation is an important means for earth science to obtain qualitative and quantitative data of research objects. Through instrument observation, we can understand the physical and chemical properties, static characteristics and dynamic changes of parameters of the research object, and provide basis for scientific analysis and reasoning. Instrument observation provides conditions for earth research to enter the scientific track. For example, the invention of meteorological instruments such as temperature, pressure and humidity in 16 ~ 17 century made meteorology gradually develop into a perfect discipline. Modern high-precision conventional and high-altitude meteorological instrument observation is still an important research foundation of meteorology. Similarly, instrumental observation plays a particularly important role in hydrology and oceanography. Instrumental observation plays an extremely important role in modern geophysical and geological research, in soil science research, especially in various monitoring and evaluation of environmental geology. Field instrument observation also belongs to first-hand information. In addition to various observations made by scientists for different research purposes, people often set up various fixed-point observation stations, such as meteorological stations, hydrological stations, seismic stations and environmental monitoring stations. And set up an observation network through a large number of stations in order to obtain systematic observation data.
(3) Geodetic survey
This is an ancient and rapidly developing important research method in earth science, which has played an important role in promoting the development of earth science. As early as ancient Egypt and China, people used simple surveying tools such as step survey to carry out land planning, topographic and geographical mapping and water conservancy project construction. In modern times, with the progress of measuring instruments, it gradually developed into traditional geodetic leveling and geodetic triangulation. The ocean detection technology (sonar) developed in the middle of 20th century played a decisive role in the development of oceanography and the revolution of geology. The laser ranging and global positioning system (GPS) developed in recent years has brought far-reaching influence to earth science. Geodetic methods are very important for the study of geography, geology, oceanography, hydrology and soil science.
(4) Aviation, aerospace and remote sensing technology
Modern aviation, aerospace and remote sensing technology have greatly promoted the development of earth science and become an indispensable and important research means in modern earth science. Because of the vast space of the earth, it is necessary to make full use of aviation, aerospace and remote sensing technologies, such as satellite cloud pictures, satellite remote sensing images and aerial photographs, to obtain information of large areas in a short time, especially the dynamic changes of large areas. Aviation, aerospace and remote sensing technologies have played a decisive role in the development and progress of modern meteorology and become its important pillars. They are also the main research methods of modern oceanography and geography, and also play an important role in modern geology, pedology, hydrology and environmental geography.
(5) Laboratory analysis, testing and scientific experiments
This is a research method widely used in various disciplines of earth science. It mainly obtains various samples or specimens from the research object, and then analyzes and tests them in the laboratory, thus obtaining qualitative and quantitative information such as the composition, structure, physical and chemical properties and formation history of the substance, and infers its formation, evolution process and development trend through scientific experimental analysis. With the development of science, the experimental science in earth science has made great progress. However, due to the complexity, long time and wide space of natural process and the limitation of modern experimental technology, it is sometimes difficult to carry out real experiments in earth science. Therefore, in earth science, we often simplify the influencing factors, create some specific physical and chemical environments, and simulate the causes, processes and development laws of natural phenomena. This method is called simulation experiment. The simulation experiment can only be approximate, and the experimental results often have a certain gap with the natural process, but it plays an important role in reproducing the process of natural phenomena and verifying and exploring the laws of earth science.
(6) Historical comparison method
This is the most basic methodology of geology. A long time has decided that geology must be studied by historical and dialectical methods. Although it is impossible for human beings to witness the whole process of geological events, we can infer the conditions, processes and characteristics of ancient geological events by using the geological phenomena and results left over from various geological events and the laws of current geological processes. This is the principle of the so-called "historical comparison method" (or "realism principle"). This principle was put forward by British geologist C Lyle (179 1 ~ 1875, the founder of modern geology) in Hutton (J Hutton, 1726 ~ 1797, a Scottish geologist, called. Lyle clearly pointed out: "Now is the key to understanding the past." For example, modern corals only live in a warm, calm and clean shallow sea environment. If coral fossils are found in rocks formed in ancient times, it can be inferred that these rocks were also formed in warm and clean shallow sea environment in ancient times (Figure 0-4); Another example is that the current volcanic eruption can form a special kind of rock-volcanic rock. If ancient volcanic rocks are found in an area, it can be inferred that there was a volcanic eruption in this area at that time, and so on. Historical comparison method is an analytical reasoning method to study the history of the earth's development, and its proposal has played an important role in promoting the development of modern geology.
Figure 0-2 British geologist Lyle
(C. Lyle, 179 1 ~ 1875)
Figure 0-3 Scottish geologist Hutton
(Hutton, 1726 ~ 1797)
Figure 0-4 Coral living in warm and clean shallow water
A- modern corals; Coral fossils from more than 200 million years ago
The theoretical basis of this principle is "variational method". Variational method holds that in the long geological history, the evolution of the earth has always been carried out in a gradual way, and its way and result are consistent both in the past and now. However, the study of modern geology proves that the viewpoint of variation theory is one-sided and mechanical. The evolution of the earth is irreversible, and now it is not a simple repetition of the past, but both similar and progressive. For example, many studies in geology reveal that the composition, quantity, temperature and pressure of the surface atmosphere, hydrosphere and biosphere, as well as the internal structure and structure of the earth or crust, are constantly changing during the evolution of the earth, which is different from the modern situation to varying degrees, which will inevitably lead to a series of different characteristics of the geological action mode and process at that time. The evolution of the earth does not always take the form of gradual change and uniform change, but there are some short and drastic changes in the process of uniform change. For example, sudden changes in material composition and structure are often found in rock formations; In the evolution of paleontology, it is often found that a large number of biological species suddenly became extinct in a short time, such as the rapid extinction of dinosaurs about 65 million years ago. Therefore, the development process of the whole earth should be a gradual-radical-gradual progressive reciprocating development process, which also conforms to the philosophical law of quantitative change-qualitative change-quantitative change.
Therefore, when using historical comparison method, we must be guided by historical, dialectical and developing ideas, rather than simply and mechanically "discussing the past from the present", so as to draw a correct conclusion. In fact, the analytical method of "from the present to the ancient" in geology has important reference significance for the study of geophysics, geochemistry, geography, meteorology, hydrology, oceanography, pedology, environmental geoscience and other disciplines in earth science.
(7) Comprehensive analysis
The complexity and irreversibility of natural processes determine that geoscience must adopt the research method of comprehensive analysis. In the long process of earth evolution, natural effects in different periods and in different ways (physics, chemistry, biology, etc.). ) and different environments (surface, underground, air, etc. ) leaves us with a complicated result pattern. In order to restore and analyze the development process of nature according to this model, it is necessary to use multidisciplinary principles and methods and combine complex influencing factors for comprehensive analysis. This is very different from mathematics, physics, chemistry and other disciplines that rely solely on deduction and experiment to learn. For example, in geology, because the process and influencing factors are very complicated, according to some individual characteristics, using the principles and methods of a single discipline often leads to one-sided or even wrong conclusions, which is the problem of "multiple solutions" or "uncertainty" often encountered in geological research. Therefore, only on the basis of comprehensive research in all aspects can we draw a unified and most practical conclusion.
(8) Application of computer technology
Some people say that since the second half of the 20th century, human society has entered the computer age, and the application of computer technology has brought profound influence and revolutionary changes to various natural sciences. The same is true of earth science. For example, in modern meteorology, geography, geology, geophysics, oceanography, environmental geoscience and other fields, computer technology has played a huge role and become an indispensable research means and method. Moreover, computer technology is infiltrating into all fields of earth science. The application of computer technology has brought infinite prospects for solving the problems in earth science, such as vast research object space, large amount of observation and processing data, and complex simulation formation and evolution process. Therefore, in order to improve the research level of earth science, we must pay full attention to, strengthen and further develop the application of computer technology in earth science.
The "Digital Earth" project or "Digital Earth" research, which began to rise widely in the world at the end of the 20th century, is the product of the combination of modern computer technology, information science and earth science. "Digital Earth" mainly discusses the method of quantitative and digital description of the whole earth system by using modern computer technology and information science, and establishes a related "Digital Earth" resource platform to serve the research and application of earth science. Therefore, "digital earth" is essentially a digital representation of the earth system, and its basic theoretical support mainly includes two interrelated aspects, namely, the theory related to earth science and the theory related to digital technology. The successful development and wide application of geographic information system, which rose earlier than digital earth, can be said to have laid a good foundation for the rise and development of digital earth. But "Digital Earth" will cover all branches or fields of earth science (not just geography), and the scientific content and data involved are incomparable to "Geographic Information System". 1998 65438+ 10, the former vice president of the United States put forward the concept of "digital earth" for the first time at the annual meeting of "Open GIS Alliance", and thought that "digital earth" refers to a virtual system with multi-resolution massive data and multi-dimensional display based on earth coordinates. As soon as the concept of digital earth was put forward, it immediately attracted the attention of the whole world and achieved rapid development. The research and realization of the digital earth has a very broad application prospect, such as the monitoring and management of resources and environment, the prediction, forecast and prevention of climate and various natural disasters, the planning of land use and various production and life, and the handling of some crisis events. It also provides an excellent resource platform for earth science education and multidisciplinary research, and especially creates favorable conditions for the study of the interaction between circles, global change and human sustainable development in earth system science.
The working methods of earth science research usually have the following procedures:
(1) data collection
According to the subject to be studied and the problem to be solved, collect all kinds of relevant data, samples and other materials as detailed, objective and systematic as possible. Data sources include detailed field investigation, instrument observation and collection, analysis of existing data and results, etc.
(2) induction, synthesis and reasoning
Using the research methods and principles of earth science, the collected data are processed, summarized and synthesized, and the inference that conforms to the objective reality is made.
(3) Verification of reasoning
Verify or test whether the inference is correct through production practice or scientific experiment, and constantly correct mistakes, improve understanding and sum up laws in the process of practice.
Earth science is a practical science. Through continuous scientific practice, people have gradually formed many hypotheses and theories. The hypothesis is based on some objective phenomena and needs further verification. A theory is a theory or proposition that has been tested by practice and formed in an academic field. Hypothesis and theory play an important role in promoting the development of earth science. They pointed out the direction for exploring the objective laws of earth science and played a certain guiding role in practice. At the same time, it is constantly tested, supplemented and revised in practice to make it more and more perfect. Of course, some assumptions and theories may also be abandoned or denied in practice.