Chapter 1
The Nature of Geology and Geophysics


1.1 Geology and geophysics, geology in particular, are sciences which have traditionally been concerned with a study of the earth. Geology relates to the solid earth itself, and geophysics to the physical properties of the earth and its atmosphere.

1.2 Besides these two, there are other sciences connected with studying the earth and its environment. Examples are: oceanography (the oceans), meteorology and climatology (the atmosphere), pedology (the soil), and space and planetary sciences (outer atmosphere and space). Although there has been a relatively close inter-action between geology and geophysics - fostered in part by exploration and development of petroleum and other mineral resources - most of these other sciences have tended to be somewhat isolated from one another. But in recent years this long and artificial separation has been disappearing - scientists engaged in studying the earth came to appreciate similarities and interactions in their studies. Consequently in the past few decades all of these sciences came to be classified as "earth sciences" or, more recently, the "geosciences". For example, according to one author: "Earth science is a blanket name for all the sciences that collectively strive to understand the earth and its space neighbours".

1.3 Grouping the several sciences involving the earth and its environment under a common broad classification led to the formation of organizations having "earth science" or "geoscience" in their title. One such organization is the Canadian Geoscience Council (CGC) founded in 1972 (see chapter 6).

1.4 The importance of the earth sciences or geosciences to society and human-kind is well-expressed in the Canadian Geoscience Council's careers booklet. Some portions are reproduced below:

Earth scientists have the responsibility of finding new mineral resources for the economic development of all nations, both rich and poor. They have to contribute to the protection of the planet and its resources by looking at soil deterioration, at the cost and location of structures, to determine sources and management of water supplies, to provide adequate energy resources, and to see that waste products are managed or stored so that they pose a minimal threat to planetary ecosystems. They also contribute a vital component to the understanding and prediction of natural hazards and disasters, including earthquakes, landslides, volcanic eruptions, floods, droughts and tidal waves.

A modern industrial society such as Canada depends directly on the availability of natural resources and the ability to process those resources. In turn, the discovery and development of earth resources depends directly on the skills of geoscientists.

Humans have come to reassess their role in the geological environment. Many questions have been raised which are of direct relevance to the earth sciences. For example, where should radioactive and chemical wastes be disposed? What is the environmental impact of a new mine? Should quarrying be done in a beautiful escarpment or should construction aggregates be obtained from more distant sources, thereby using up more energy and contributing to global warming? Is it possible to assess the computer-predicted degree of climate warming by examining proxy environmental data? Can a watershed support a large park area and tourist visits without permanent disruption or damage? What are the full environmental consequences of river diversion in order to service human needs? Such questions result in decisions made or influenced by geoscientists.

1.5 Notwithstanding the increasingly common usage of the general terminology, geology and geophysics continue to be considered as two specific and major fields of endeavour by many scientific and professional organizations, including APEGGA. This is the philosophy inherent in this publication, and it should be kept in mind that usage of the terms "earth science" and "geoscience" apply to other fields, (or sciences, or disciplines), as well as geology and geophysics.


1.6 From the dawn of the stone age accelerating with the discovery of metals, man has been dependent on his mineral resources. Today, the economy is based more than ever before on the earth's natural mineral resources. The increasing awareness of man's dependence on these natural resources eventually led to a fascinating and vital new science - geology, the science of the earth.

1.7 The word geology is literally self-defining, for it is derived from the Greek "geo" (earth) plus "logos" (study). Unlike such sciences as astronomy, mathematics and physics, geology as known today has developed during the past three hun-dred years. The word itself was coined less than two hundred years ago.

1.8 Through the Renaissance, the basic tenets of geology were slowly evolving, But this progress was sporadic, consisting of scattered and often unrelated obser-vations. Certain geologic principles had been recognized, but they had not been clearly defined or related to each other, and geology lacked a basic unifying concept that might give it the status of a true science. In 1795, this unifying concept was provided, when James Hutton published the book "Theory of the Earth, with Proofs and Illustrations". Clarified by John Playfair, Hutton's principle of Uniformity of Process became the basis of most geologic interpretation and one of geology's contribution to modern scientific thought.

1.9 Geology continued to develop in the 1800s and beyond. An earth sciences encyclopedia states: "During the twentieth century the skills of the geologist have been in constant demand and the geological profession has expanded enormously. The technology basic to modern society lays strenuous claims upon all manner of materials locked into the earth's crust, and the discovery of these materials has become one of the prime tasks of the Earth Scientist."


1.10 The term "geophysics" first appeared in 1853 when a German lexicon used it as a substitute for the term "earth physics". According to Matthews, geophysics is an "in between" field that employs the techniques and concepts of both physics and geology. Another text designates geophysics as "the study of the earth using physical measurements at or above the surface" and comments as follows: "Geology involves the study of the earth by direct observations on rocks, either from surface exposure or boreholes, and the deduction of its structure, compo-sition, or history by analysis of such observations. Geophysics, on the other hand, involves the study of those parts of the earth hidden from direct view by meas-uring their physical properties with appropriate instruments, usually on or above the surface. It also includes interpretation of the measurements to obtain useful information on the composition and structure of the concealed zones."

1.11 The Canadian Society of Exploration Geophysicists (SEG) describes geo-physics as follows: in applying the principles of physics, it is the science that studies the physical properties of both the interior of the earth , and the properties of the atmosphere. The properties of the earth's interior that are measured include the travel time and velocity of seismic energy (motion) through the earth, rock density, magnetic field, electrical properties, radioactivity and others. The results of these measurements are used to:

1. locate stable areas for the construction of dams and buildings;

2. determine the location and strength of earthquakes;

3. explore the recoverable resources of

a) petroleum and natural gas
b) minerals
c) fresh water and
d) geothermal reservoirs;

4. study the internal structure of the earth; and

5. study the evolution of the earth.

Geophysical investigations of the atmosphere extend to the exosphere and beyond, but this aspect of geophysics is outside the scope of Alberta practice (see para-graph 1.12 below).

Formal or Legal Definitions

1.12 The Engineering, Geological and Geophysical Professions Act defines the practices of geology and geophysics as follows:

'Practice of Geology' means:

reporting, advising, evaluating, interpreting, geological surveying, sampling or examining related to any activity

(a) that is aimed at the discovery or development of oil, natural gas, coal, metallic or non-metallic minerals, precious stones, other natural resources or water or that is aimed at the investigation or geological conditions, and

(b) that requires in that reporting, advising, evaluating, interpreting, geological surveying, sampling or examining, the professional application of the principles of the geological sciences.

'Practice of geophysics' means:

reporting on, advising on, acquiring, processing, evaluating or interpreting geophysical data, or geophysical surveying that relates to any activity

(a) that is aimed at the discovery or development of oil, natural gas, coal, metallic or non-metallic minerals or precious stones or other natural resources or water or that is aimed at the investigation of subsurface conditions in the earth, and

(b) that requires in that reporting, advising, evaluating, interpreting, or geophysical surveying, the professional application of the geophysical sciences.

These definitions were developed in 1980-81 by the APEGGA Act and Bylaws Committee during drafting of the new Act. The Committee had representation on it from senior geologists and geophysicists, and input was received from the geological and geophysical membership of APEGGA during the approval process through Council and the membership.

1.13 It is worth noting that both definitions refer to "the professional application of the geological/geophysical sciences". In this sense, the geological sciences can be considered as subdivisions of geology, such as mineralogy, petrology, paleontology, geomorphology, structural geology. Subdivisions of geophysics include atmosphere physics, hydrosphere physics, solid earth physics, of which the latter subdivision can be further broken down into seismology, geoelectricity, tectonophysics etc.

1.14 The definitions have both similarities and differences. Subsections (a) of both definitions, which describe the "activities" involved in practising geology or geophysics, are similar in that both refer to the discovery or development of:

  • oil
  • natural gas
  • coal
  • minerals (both metallic and non-metallic)
  • precious stones
  • water
  • other natural resources

In other words, both geologists and geophysicists are concerned with these specific resources, and with both the discovery and development of them. Another similarity between the two definitions is the final phrase in subsection (b) - :"that requires in the ... (performing) ... the professional application of the principles of the geological (in the case of geology) and of the geophysical (in the case of geophysics) sciences." Hence a formal education is required to legally practice geology and geophysics - the practice cannot be carried out by those not appropriately educated and trained - and this is consistent with treating geology and geophysics as profes-sions.

1.15 Further examination of the definitions contained in the Act shows some dissimilarities i.e. there is one activity which is distinct for each profession, and that what geologists do is sometimes different from what geophysicists do:

  Geologists Geophysicists
Activity that is aimed at the investigation of geological conditions. that is aimed at the investigation of subsurface conditions in the earth.
What is done
  • reporting
  • advising
  • evaluating
  • interpreting
  • geological surveying
  • sampling
  • examinging

  • reporting on
  • advising on
  • acquiring, processing and interpreting geophysical data
  • geophysical surveying

1.16 The definitions of practice include also the teaching of geology and geo-physics at a university. In 1983-84 this inclusion generated some concern among university academic staff who came to view the requirement as an encroachment on academic freedom and interference with university hiring practices. The out-come was an additional clause exempting from the practice of the profession a person whose work consisted exclusively of teaching geology or geophysics at a university, but "teaching" continued to be specified in the definition.

Are Geology and Geophysics Also Professions?

1.17 Most geologists and geophysicists regard their calling as a profession. Some, while viewing these sciences as professions, either do not feel their professions should be legally recognized or if legally recognized, they see no need to belong to it. While this question is examined in more detail in Chapter 3, a short discussion on the meaning of the term "profession" is in order at this stage.

1.18 There are various definitions of the word "profession" in the literature. For example, according to Webster's Unabridged Dictionary, a general meaning is "A calling requiring specialized knowledge and often long and intensive preparation including instruction in skills and methods, maintaining by force of organization or concerned opinion high standards of achievement and conduct, and committing its members to continued study and a kind of work which has for its prime purpose the rendering of a public service."

1.19 Wickenden in "The Second Mile", in listing the attributes of the corporate life of a group of persons as professional in character, states a similar meaning:

1. A body of knowledge (science) and of art (skill) held as a common possession and to be extended by united effort;

2. An educational process based on this body of knowledge and art, in ordering which the professional group has a recognized responsibility;

3. A standard of personal qualifications for admission to the professional group, based on character, training and proved competence;

4. A standard of conduct, based on courtesy, honour and ethics, which guides the practitioner in his relations with clients, colleagues and the public;

5. More or less formal recognition of status, either by one's colleagues or by the state, as a basis for good standing; and

6. An organization of the professional group, devoted to its common advancement and its social duty, rather than to the maintenance of an economic monopoly.

1.20 The Alberta Government report on the professions and occupations referred to the traditional definition of a profession as "an occupation that properly requires a liberal arts education (the higher branches of learning enhancing the languages, history, science and philosophy) or its equivalent and mental rather than physical labour". The report also states that "the professions are quite conscious of the designation as a 'profession' and have invariably interpreted it to mean a branch or field of endeavour which for ideal performance, requires an advanced degree of aptitude, ability, specialized training, responsibility, conscientiousness, self-discipline and ethical maturity".

1.21 A third definition, which is oriented towards the individual and which is contained in legislation, is the definition of a professional employee in the U.S. Taft-Hartley law:

The term 'professional employee' means -

(a) any employee engaged in work

(i) predominantly intellectual and varied in character as opposed to routine mental, manual, mechanical or physical work;

(ii) involving the consistent exercise of discretion and judgement in its perform-ance;

(iii) of such a character that the output produced or the result accomplished cannot be standardized in relation to a given period of time;

(iv) requiring a knowledge of an advanced type in a field of science or learning customarily acquired by a prolonged course of specialized intellectual instruction and study in an institution of higher learning from a general academic education or from an apprenticeship or from training in the performance or routine mental, manual or physical processes; or

(b) any employee who

(i) has completed the course of specialized intellectual instruction and study described in clause (iv) of paragraph (a), and

(ii) is performing related work under the supervision of a professional person to qualify himself to become a professional employee as defined in paragraph (a).

1.22 There are numerous other definitions and meanings of "profession" as well as those described above, but most of these have common characteristics which consistently appear. To illustrate, the following is an excerpt from APEGGA's Manual of Practice:

A profession is a learned calling with specialized skills, distinctive functions and recognized social obligations and has unique characteristics.

o It renders services based upon advanced knowledge, skill and judgement.
o It is charged with a substantial degree of public obligation and performs its services largely in the general public interest.

o It is bound by a distinctive ethical code in its relationships with clients, employees, colleagues and the public.

o It assumes responsibility for actions related to professional services provided in a personal or supervisory capacity.

Professions such as engineering, geology and geophysics are generally highly organized; they have definitive standards of admission (which are minimum standards only and make no distinction between the least competent persons and the outstanding leaders of the profession); they regulate the activities of their members; they promote the advancement of knowledge, skill and experience; and they encourage the formulation of standards. While professionals should be fairly remunerated for their services, their members are expected to put service above gain, excellence above quantity, rewards of self-expression above any pecuniary incentive, and a code of honour above competitive spirit.

1.23 In comparing the definitions of geology and geophysics with the definitions of a "profession", it is evident that both can be regarded as professions. However, in the case of geophysics, the degree to which that profession has satisfied one of the characteristics - protection of the public interest - has sometimes caused some difficulty (see Chapter 3).

1.24 Organized geosciences associations and societies treat geology and geo-physics as professions. Statements in the literature of the American Institute of Professional Geologists (AIPG) clearly show the status of the geology profession accorded by this organization: "The purpose of the Institute shall be: to strengthen the geological sciences as a profession ..."; "AIPG remains dedicated to communi-cating to the public and to its representatives the importance to society of the profession of geology"; "AIPG strives to promote awareness of the profession of geology and contends that professional geological work provided to the public should be undertaken by qualified geologists"; "It is in the best American tradition for members of a profession to group together in an association"; "Geology is both a science and a profession." The Society of Exploration Geophysicists (SEG) requires, for membership, the applicant's work to have been of a professional nature for not less than the eight years of professional experience; its Code of Ethics contains statements such as "It shall be your duty as a geophysicist, in order to maintain the dignity of your chosen profession: to ... carry on your professional work ... coop-erate in building up the geophysical profession ...". The State Board of Registration for Geologists and Geophysicists, California was given specific authority to "regu-late the geology and geophysics professions ..." under the California Act. The Board of Registration for Professional Geologists, State of Idaho, begins its Code of Ethics with the sentence "Geology is a profession, and the privilege of professional practice requires morality and responsibility, as well as professional knowledge, on the part of the practitioner."

1.25 Remarks by a U. S. consulting geologist, Wallace E. Pratt, on the certification of professional geologists are noteworthy in referring to geology as a profession:

Although petroleum geologists have long devoted themselves with commendable zeal to their science, represented by the American Association of Petroleum Geologists, most of those employed by the oil industry have in the past manifested only an indifferent attitude toward geology as a profession. Only within the last few years have petroleum geologists begun to realize that they constitute a profession, as well as a science; and that their profession demands of them the same loyalty they have long rendered to their science.

But do we all agree that petroleum geology is a profession as well as a science? The term professional has been defined authoritatively as an occupation based on an art, a science, or other branch of learning, in which each of those who engage in it professes to be skilled, experienced, and competent - capable of applying his profession constructively to the affairs of others. Divinity, medicine, and law have long been recognized as three learned professions. This definition would surely include geology, in particular petroleum geology, among the professions, and the close analogies of the practice of the petroleum geologist with those of well-established professions are conspicuous.

For many years the legal and medical professions have each maintained self-established and self-administered standards which determine the eligibility of all applicants for membership. These standards are not only subject to approval by an appropriate agency of government, state or local, but also their rigid maintenance is enforced by law. I believe that this same professional responsibility must be assumed by our own profession as, more and more, it comes to serve the public. If we geologists do not ourselves establish and put into effect standards of profes-sional adequacy, government will set up its own standards. In either case the professional geologist will be required by law to conform to those standards.

1.26 In "Geophysics in the Affairs of Man" the authors make frequent reference to geophysics as a profession. Chapter 1 of this book is entitled "Some Ante-cedents to the Modern Day Profession of Geophysics Through World War I". Some other examples are: "... the development of the geophysical profession during the 1800s was a very slow one and largely academic in nature"; "Because the profession was young, the people in it were young." (1920s - 1930s); "Salary levels and job openings within the profession are also excellent, particularly on the industrial side." (1970s - 1980s)

Branches of Geology and Geophysics

1.27 For many years, the profession of engineering has been subdivided or classified into several different branches, the more common being mechanical, aeronautical, civil, electrical and chemical. There are many different engineering degree programs, which correspond to the various branches, offered at Canadian and American universities with new programs being introduced at a substantial rate. Similarly, the geological and geophysical professions can also be classified into branches or divisions.

1.28 There are several ways of subdividing the geosciences professions (geology and geophysics), but in reality no clear boundaries exist between the many fields. Generally, most Canadian geologists begin their studies with concentration on igneous and metamorphic rocks if they have a career in mining in mind, or else in the study of sedimentary rocks, which emphasizes the nature of the younger, sedimentary cover (less than 600 million years old), and commonly leads to a career in the oil and gas industry. Most geology or earth science departments in Canada offer a basic background in the two areas; some will concentrate on only one. Programs in geophysics do not fit this pattern.


1.29 The generally accepted branches of geology are listed as follows along with a brief description of the characteristics or nature of each.

1.29.1 Petroleum Geology

Petroleum geology, according to a publication of the American Geological institute, is that branch of geology which relates to the origin, occurrence, migra-tion, accumulation and exploration for hydrocarbon fuels. Its practice involves the application of geochemistry, geophysics, paleontology, structural geology and stratigraphy to the problems of finding hydrocarbons. Thus a petroleum geologist is a geologist who is engaged in the exploration or production processes of hydrocarbon fuels.

It takes a considerable amount of skill and expertise to locate petroleum, and the petroleum geologist must be well versed in stratigraphy, sedimentology, structural geology and geophysical techniques to make interpretations of the geology so that the chance of discovering economic hydrocarbons is increased. The petroleum geologist's work has its descriptive and interpretive aspects, but the emphasis is on the descriptive because the goal is a deterministic model of the area under study - ultimately, the oil or gas field.

1.29.2 Mining Geology

The mining industry in its task of finding, following and extracting metallic ores has always made use of geology in one way or another. Writings on mining since medieval times all venture into discussions of ore genesis and ore local-ization; naive and amusing as they may seem now, they are the best geology known at the time and were, even then, considered part of the knowledge essential to mining. Until geologists began to take an interest in the specialized problems of mining, each miner or engineer had to be his own geologist, applying as best he could, and often with marked success, the ideas that he gained from science or developed by himself. Only during the last century, and particularly during the last generation, have those aspects of geology that are applicable to mining been developed to such a degree as to form the basis for a separate branch of the profession.

In these days most projects for the exploration and development of metals are carried out under some form of geological guidance, whether it is supplied by professional geologists or by engineers who have themselves acquired a knowledge of geology, and whether it is based on original investigation or on surveys by government or scientific organizations.

Of the professional geologists who devote their attention to matters bearing on mining, many, but by no means all, are employed by mining companies. A large group are in government employ, and a few are engaged by organizations concerned with the financial aspects of mining.

1.29.3 Engineering Geology

As defined by the Association of Engineering Geologists, engineering geology is the application of geologic data, techniques and principles to the study of rock and soil surficial materials and groundwater, for the proper location, planning, design, construction, operation and maintenance of engineering struc-tures. Engineering geology is commonly tied in with environmental geology, or hydrogeology.

Like geological engineers, engineering geologists are expected to solve practical engineering problems. They assess the natural foundation conditions for buildings, bridges, dams and reservoirs, power plants, pipelines, highways, canals, sewers, tunnels, mine adits and harbours. Design of these structures requires a thorough knowledge of the mechanical properties and stability of the rocks and sediments that will carry them.

Engineering geologists assess the anticipated impact of subsidence, rains, floods, landslides, volcanoes and earthquakes on these structures. They explore the physical and chemical properties of structural materials (sand, gravel, cement, clay) and water in the vicinity of construction sites. They advise on planning and location of new urban and industrial development in cities, particularly waste disposal sites, and particularly those for the disposal of nuclear wastes. For arctic climates, engineering geologists are focusing increasing attention on permafrost problems.

1.29.4 Hydrogeology

Hydrogeology or groundwater geology, as it is sometimes termed, is the study of occurrence, movement and qualitative-quantitative aspects of water, particularly subsurface water. Agricultural, industrial and residential regions require large quantities of pure, uncontaminated water, often beyond that readily available at the surface.

The hydrogeologist's task is to find these hidden subsurface water resources, assess their quality and determine reservoir potential. In addition, the hydro-geologist is often directly involved in major assessment studies, where the problem of water pollution or the problem of chemical or radioactive waste disposal is critical. Many, if not most, hydrogeologists operate as consultants to industry or government.

1.29.5 Environmental Geology 27

Environmental geology is the study of the interaction between the surficial layers (rocks, sediments and soils), the waters in or on them, the atmosphere and the organisms, especially man, that occupy all three. One of the most important components of environmental geology is stratigraphy, with data largely supplied by test drilling, geophysical techniques and geological engineering.

In Alberta, the most important aspect of environmental geology is glacial geology and groundwater (including physical characteristics of the materials).

Environmental geologists are closely involved in teams, commissions or enquiries that analyze the impact on the environment caused by development of underground or surface mines, by diversion of rivers or lakes, by expansion of urban or industrial areas at the expense of wilderness and agricultural zones and waste disposal. They work alongside hydrogeologists, glacial geologists, engineers, biologists and chemists. They provide geotechnical engineers with the necessary geological framework. Such geologists are in the forefront of decision making when nuclear or chemical waste disposal problems are being resolved. In effect, the environmental geologist is expected to provide information that will buffer or minimize man's contact with nature.

Because environmental geologists deal not only with the surficial deposits, but also with the bedrock underneath, their university background must be solid in the fields of stratigraphy, sedimentology, structures, geomorphology and geol-ogical processes and models.

1.29.6 Marine Geology

Also known as geological oceanography, marine geology is that aspect of the study of the ocean which deals specifically with the ocean floor and the ocean-continent border. It includes submarine relief features, the geochemistry and petrology of the sediments and rocks of the ocean floor and the influence of sea water and waves on the ocean bottom and its materials.


1.30 Branches of geophysics are less easily defined than those of geology. The more common ones are listed as follows.

1.30.1 Petroleum Geophysics

Petroleum geophysics is a true remote sensing process in which an observer near the surface of the ground records the physical response of the subsurface sedimentary rocks to certain applied natural or induced energy, and interprets the recordings for the purpose of locating and defining hydrocarbon deposits. The properties sensed are generally divided into two major classes: potential fields and seismic signals, most commonly reflections, but also refraction. The data acquired is similar onshore and offshore, but logistics dictates substantial differences in operations conducted over land and over water.

Definition of the subsurface falls into two major categories: structural, which seeks to describe the existing shape and tectonic history and, more recently, stratigraphic, which endeavours to determine the nature and depositional history of the sediments.

Raw field data is normally distorted and contaminated by noise and other unwanted signals. Signal enhancement and reduction of field data forms a major intermediate activity, following which the data are interpreted. Although quanti-tative measurements are made, the measured response usually represents the sum of a number of components and conditions, leaving considerable room for ambi-guity in the interpretation. Therefore, as is the case with geology, professional opinion and judgement are heavily involved, and the results normally benefit from long and varied experience in professional practice.

Petroleum geophysics draws experts from many disciplines, in order to cover the diverse activities required by the industry. These include graduates in the fields of geology, physics, mathematics, electrical engineering and computer science in addition to geophysics.

1.30.2 Mining Geophysics

Mining geophysics plays an important role in the exploration for new mineral deposits. This branch of geophysics involves data collection using sensing devices on aircraft or on the ground, and data processing which includes manipu-lation of the data to draw conclusions about where ore bodies may occur, and preparation of graphs and maps of such data.

Mining geophysics involves the location, through remote sensing of physical properties, of subsurface mineral concentrations i.e. (anomalies) eventually to be proven by diamond drill sampling as either valuable or worthless. Since only one in two hundred to one in five thousand anomalies prove to be ore bodies, it is economically essential for mining geophysicists to select only the most promising anomalies for further investigation. In this process they work in close liaison with a team of other earth science specialists, usually under the supervision of an economic geologist.

In mining geophysics, the nature of subsurface geology can be determined using a range of instruments employing the electromagnetic spectrum from D.C. through 100 megahertz and even to a million, trillion megahertz, if radioactive radiation detection instruments are included. With a gravity meter having a sensitivity of one part in 108 thousand, the increase in gravitational attraction over a heavy mineral ore body can be detected.

Data processing in mining geophysics is a relatively new and rapidly developing industry. The introduction of the minicomputer and the microprocessor has enabled geophysical data to be collected in digital form even under the typically difficult survey environment. This increasing availability of digital data has stimulated the use of computers for the compilation and interpretation of data.

The computer enables the mining geophysicist to perform a variety of corrections, enhancements and transformations. Since the interpretation of geo-physical data is highly dependent on the visual presentation of information, computer graphics are a key element in the process.

1.30.3 Seismology

Seismology is the branch of geophysics which uses the ability of rock layers of different densities and therefore different acoustic velocities to transmit shock waves to determine the nature and structural attitude of rocks deep below the surface. Reflection occurs at the interface between layers. In very practical ways, this is used by the petroleum industry to find oil and gas prospects. Artificial shocks are generated and detected via geophones at several widely separated locations. The data is then computerized to produce a seismic cross-section.

The extreme sensitivity of current seismic techniques has led to seismic stratigraphy, a highly sensitive tool in oil exploration and correlations. Seismolo-gists also interpret the shock waves produced by natural earthquakes of rock units to provide interpretations of deep-seated crustal activity and major movements of plates. Improvements in earthquake prediction come from such studies, especially when tied into satellite imagery and precise measurements of distance using laser-ranging techniques.

1.30.4 Petrophysics 30

Rocks have specific capacities to conduct electricity; having their own natural electrical potential, an induced current can provide data concerning the types of rocks present, their porosity and permeability and the nature of the fluids trapped within the rocks. When this became known in the 1920s a whole new field of geological-geophysical exploration was set up in the oil industry, namely well logging or petrophysics. Geophysicists now routinely test the wells drilled and provide accurate indications of the succession of rocks penetrated by their holes. Many other techniques are used to supplement electric logging: neutron, nuclear magnetic resonance, temperature, gamma-ray logging and others.

1.30.5 Engineering Geophysics

Engineering geophysics generally involves geophysical investigations in support of large engineering projects, in the planning, construction and operational use stages. Engineering geophysicists may participate in site evaluations for major projects such as hydroelectric reservoirs and nuclear power plants. They may investigate ground conditions in polar regions, for example, to determine the location of permafrost and in earthquake and volcanic-prone areas to determine risk and zoning.

One class of problems in which engineering geophysicists play a significant role is the investigation of existing structures and their foundations. These prob-lems have recently become more significant because of an aging and decaying infrastructure, and the remedial efforts are directed towards increasing the useful life of the structure and ensuring public safety. One example is the examination of earth and rockfill dams to investigate the anomalous seepage through, under or around the dam. Investigations of this nature are also important because struc-tures such as freeways near San Francisco may have been built without adequate appreciation of the risk of earthquakes.

Seismic and electrical geophysical methods are the ones that are used more widely in engineering studies, for they measure elasticity and fluid content properties respectively. While seismic methods are not particularly sensitive to the presence of cracks or fluids, electric methods respond quickly to the ions contained in the fluids that often populate cracks in rock formations. Electromagnetic methods measure the electrical conductivity of rock at frequencies from 0 to many megahertz. Interpretation of the results requires experience and skill on the part of the engineering geophysicist.

Using equipment refined from that of large-scale earthquake seismology, engineering geophysicists measure the degree of seismic activity in an area including small earthquakes to estimate the risk of a large event. Geologic obser-vations may also be integrated with geophysical data to produce a composite risk assessment.

The seismic and ground movement precursors to volcanic eruption are reasonably well understood. Engineering geophysicists monitoring ground move-ment using effective surveying techniques and seismic activity with good event detecting seismic recorders can often provide a warning of impending volcanic eruption a few days to hours in advance.

Relationships between Geologists and Geophysicists

1.31 Neil J. Smith of Chevron Oil Company, as President of the Society of Exploration Geophysicists (SEG), in 1967 gave a presidential address on this topic. Mr. Smith was a geologist by training and a geophysicist by practice, and thus felt he was qualified to discuss such relationships. Portions of his address are repeated below.

If one goes back in time for 45 years, the geologist, young, happy, and bright, was beginning to run out of surface structures. About then the torsion-seismic method followed, and then the reflection-seismic method.

The techniques were applied at the onset by physicists, as only a few could claim the 'geo' prefix. These men, trained to find rigorous proofs and record repeatable measurements, did not easily communicate with the geologist. The geologists by training was not interested in the rock parameters which the physicists were measuring. Density differences and formation velocities were intangible. What the geologist thought was 'thinking big', the physicist thought was 'sloppy thinking'. They might not have cooperated at all except that the newcomers, during their first impacts, made finding oil like 'shooting fish in a barrel'.

Here were interlopers, the physicists, making changes, a natural basis for resentment - just as the Indian resented the white man, the cattleman resented the sheepman, and the Californian resented the Okie. However natural this attitude may be, it does not appear to be effective: the interlopers stay; the changes go on. Remember the case of the Indian!

Resistance and resentment were not universal. Geologists not frightened by mathematics and physics and physicists, or the electrical engineers who could appreciate the nature of geology, worked together readily. After a while they, mutually, began to be geophysicists. That was how the trouble began and how it began to disappear. If one looks squarely at the problems remaining, they are few. The peripheral squeaks and groans are from ghosts, or from those who like friction for the warmth it gives.

It would be strange if relations were not good by 1967. There is a great deal of interpenetration between the disciplines. Most companies give their geologists training in geophysics, commonly for extensive periods. On the geophysical side, more than a third of the SEG members are geologists by training. Another large fraction are either geologically oriented or are eager to be. The remainder can hardly be a source of friction, as they are largely specialists who have no need to 'interface' with the geologists to any extent.

However, I would not want to disappoint anyone by claiming no areas of friction. There are two which persist to measurable degrees. A geologist who works with geophysical data and who can manipulate them and use them properly is accepted by geophysicists as a geophysicist. It is like swimming. If a man dives into the water and swims, he is a swimmer. He is the kind of swimmer his performance shows him to be. So it is with the geologists working in geophysics.

The converse does not hold true, at least not for the geophysicist whose degree is not geological. He is viewed with consternation if he is observed swimming from point to point in the geological pool. He is narrowly observed for signs of water wings or other evidence of cheating. He is watched for deviations from local geologic fetishes. Evidence notwithstanding, he had better be wary of suggesting a down-to-the-north fault where the established thought is down-to-the-south. The attempt itself is impudence; should it prove to be correct, the credit will go to 'luck'.

However, what cannot be gained by experience and demonstration can be won by academic retreading. If he has a geology degree in hand, from night school or wherever, all is well.

This attitude is not without a basis in reason. The geophysicist tends to be broad-minded in his acceptances as is understandable in a man whose education is heterogeneous. Further, it is relatively easy to examine a man's competence in geophysical techniques, whereas geological assertions may be difficult to evaluate. Geology is somewhat like psychiatry where schools may differ so widely on important theories that a practitioner must show his diploma to be entitled to an opinion. As a geologist, I can appreciate the position; as a geophysicist, I do not like it.

There is another persistent area of minor contention. Both the geologist and the geophysicist seem to believe that the other has the 'best deal', the most appreci-ation, the surest road to advancement. I have not been able to find any consistent basis for this in either profession.

This belief may relate to the observation that, when management has a group of professionals from which to draw in order to fill a supervisory position, it seems to have trouble giving the more specialized man a chance. The less specialized man may not be able to fill the specialist's shoes. Then, more moves have to be made with attendant confusion and substantial cost. As can be seen, this is really the specialist's dilemma. The apparent bias exists only to the extent that geophysics contains a higher percentage of specialists than geology.

It would ease management's burden and conscience and resolve the specialist's dilemma in large part if management could promote a professional ladder which would meet professional and community-reward standards. This is easier said than done because neither the professional nor the community has developed mutually acceptable patterns of recognition; development seems to be underway and, perhaps, can be accelerated.

So much for these persistent but not devastating problems. We share another more serious. It is a common problem that relates to the rate of technical advance and to rates of absorption of technology. We have our own technical explosion. It has the geophysicist running very hard, trying to keep up and 'get out the wash', too. Forgive him if he seems preoccupied. He is going to intra-company schools, computer schools, seminars developed through local initiative or by professional societies and extension courses set up by universities.

Geologists, of course, share this disturbance. In the past an exploration geophysicist could keep reasonable abreast of the advances in geophysics with reasonable effort. Now a reasonable effort will not do; a most unreasonable effort is required. Because a geologist's job demands an appreciation of what the new techniques can do, and because a geologists must assimilate large amounts of geophysical data relating to the subsurface, he has no choice; he will have to 'put out' the unreasonable effort.

Geologists will have to hurry with this 'little' task, because geology is being digitized. Before long, 'deconvolution' will be a geologic term. Geophysicists are extremely interested in seeing how geologists accept it. The way to do all this is straightforward. It simply requires time, money and hard work. For the individual geologist or geophysicists it means less TV and golf, shorter weekends and more homework. For the company, it means organizational flexibility, the breaking of rigid patterns of procedure and the elimination of 'piddle work' or anything done just because it has been done.

1.32 Mr. Smith's article concludes by urging the AAPG and SEG to continue to cooperate so that geologists and geophysicists may keep up with progress in each other's fields. His final remarks are "... one must remember that, though our goals are the same, our roles are not, they are overlapping. We do not want to be so thoroughly integrated that we lose our identities."