ESC101 LM01: Why It Matters: Science of Geology PDF

**[ESC101 -- LM01]** **Why It Matters: Science of Geology** **Introduction** When you ask the question "What is geology?" most people will initially respond that it is the study of rocks. This is true, but geology is also so much more than that. What if I told you geology is an intricate part of...

**[ESC101 -- LM01]** **Why It Matters: Science of Geology** **Introduction** When you ask the question "What is geology?" most people will initially respond that it is the study of rocks. This is true, but geology is also so much more than that. What if I told you geology is an intricate part of your everyday life? You may have to stop and think for a minute about that statement, but let's consider the following questions: 1. Where do your energy resources come from---not just the gas in your car, but the components in your cell phones and tablets as well? 2. Why does Japan have so many active volcanoes and earthquakes? 3. Do you enjoy eating, cooking, or gardening? 4. Do you enjoy bottled, spring, or tap water? While some of these questions are obviously geology related, it may take some exploring to find the answers to all of them. Throughout the course, you will learn the information necessary to answer these questions and others like them. We will see that geology is not just rocks but is far more encompassing than that. However, I can't let this introduction go by without saying GEOLOGY ROCKS! **Learning Outcomes** - Define the science of geology. - Identify and use scientific processes and the scientific methods as used by geologists and with other related scientific disciplines. - List tools and concepts commonly used by geologists. **Why Do People Study Geology?** A lot of people are attracted to geology and other earth sciences because they love to be outdoors. These people wonder how the magnificent rock formations that they see, like those in Yosemite in California (see figure 1), were formed. They want to study the processes that create and modify landforms. A panoramic shot of half dome and the rock formations that surround it. The massive formations curve and rise as mountains. Figure 1. Half dome in Yosemite, National Park, California, USA But earth science is not just about what we can see with the naked eye---the molten lava, icy mountain peaks, steep canyons, and towering waterfalls. Some people want to go deeper, to learn about what drives the surface processes and other features of the planet; for example, why does Earth have a magnetic field? These people are interested in learning about the layers of material that lie beneath the surface, the mantle and the core. Since more than 70 percent of Earth is covered with oceans, it's not surprising that many people wonder what lies within and at the bottom of the seas.  Figure 2. The "Blue Marble" Some people look up and wonder what lies beyond our skies. These people are interested in applying what we know about Earth to our more distant surroundings. They want to understand our near neighbors, the planets and satellites of our Solar System, and objects that lie far beyond. **What is Geology?** In its broadest sense, **geology** is the study of Earth---its interior and its exterior surface, the rocks and other materials that are around us, the processes that have resulted in the formation of those materials, the water that flows over the surface and lies underground, the changes that have taken place over the vastness of geological time, and the changes that we can anticipate will take place in the near future. Geology is a science: we use deductive reasoning and scientific methods to understand geological problems. Geology is arguably the most integrated of all of the sciences because it involves the understanding and application of all of the other sciences: physics, chemistry, biology, mathematics, astronomy, and others. But unlike most of the other sciences, geology has an extra dimension, that of time---billions of years of it. Geologists study the evidence that they see around them, but in most cases, they are observing the results of processes that happened thousands, millions, and even billions of years in the past. Those were processes that took place at incredibly slow rates---millimeters per year to centimeters per year---but because of the amount of time available, they produced massive results. A mountain with a glacier between it and another mountain range. Figure 3. Rearguard Mountain and Robson Glacier in the Rocky Mountains of British Columbia Geology is displayed on a grand scale in mountainous regions, perhaps nowhere better than the Rocky Mountains in Canada (Figure 3). The peak on the right is Rearguard Mountain, which is a few kilometers northeast of Mount Robson, the tallest peak in the Canadian Rockies (3,954 m). The large glacier in the middle of the photo is the Robson Glacier. The river flowing from Robson Glacier drains into Berg Lake in the bottom right. The sedimentary rock that these mountains are made of formed in ocean water over 500 million years ago. A few hundred million years later, these beds were pushed east for tens to hundreds of kilometers by tectonic plate convergence and also pushed up to thousands of meters above sea level. Over the past two million years this area---like most of the rest of Canada---has been repeatedly glaciated, and the erosional effects of those glaciations are obvious. The Robson Glacier is now only a small remnant of its size during the Little Ice Age of the fifteenth to eighteenth centuries, as shown by the distinctive line on the slope on the left. Like almost all other glaciers in the world, it is now receding even more rapidly because of human-caused climate change. Geology is also about understanding the evolution of life on Earth; about discovering resources such as metals and energy; about recognizing and minimizing the environmental implications of our use of those resources; and about learning how to mitigate the hazards related to earthquakes, volcanic eruptions, and slope failures. All of these aspects of geology, and many more, are covered in this course. **The Branches of Geology** As we mentioned, there are many varieties of geology. There is so much to know about our home planet that most geologists become specialists in one area. These specialties are known as **branches of geology**, and have specific titles. For example, a mineralogist studies minerals while a seismologist monitors earthquakes to help protect people and property from harm (figure 1).  Figure 1. (A) Mineralogists focus on all kinds of minerals. (B) Seismographs are used to measure earthquakes and pinpoint their origins. A mountain with distinct layers in a chevron panel Figure 2. These folded rock layers have bent over time. Studying rock layers helps scientists to explain these layers and the geologic history of the area. Volcanologists brave molten lava to study volcanoes. Scientists who compare the geology of other planets to Earth are planetary geologists. Some geologists study the Moon. Others look for petroleum. Still others specialize in studying soil. Some geologists can tell how old rocks are and determine how different rock layers formed (figure 2). There is probably an expert in almost anything you can think of related to Earth! Geologists might study rivers and lakes, the underground water found between soil and rock particles, or even water that is frozen in glaciers. Earth scientists also need geographers who explore the features of Earth's surface and work with cartographers, who make maps. Studying the layers of rock beneath the surface helps us to understand the history of planet Earth. **Some Branches of Geology** As you've seen, different branches of geology study one particular part of earth. Since all of the branches are connected, specialists work together to answer complicated questions. Let's look at some other important branches of geology. **Geochemistry** **Geochemistry** is the study of the chemical processes which form and shape the Earth. It includes the study of the cycles of matter and energy which transport the Earth's chemical components and the interaction of these cycles with the hydrosphere and the atmosphere. It is a subfield of inorganic chemistry, which is concerned with the properties of all the elements in the periodic table and their compounds. Inorganic chemistry investigates the characteristics of substances that are not organic, such as nonliving matter and minerals found in the Earth's crust. **Oceanography** **Oceanography** is the study of the composition and motion of the water column and the processes which are responsible for that motion. The principal oceanographic processes influencing continental shelf waters include waves and tides as well as wind-driven and other oceanic currents. Understanding the oceanography of shelf waters and the influence this has on seabed dynamics, contributes to a wide range of activities such as the following: - assessment of offshore petroleum production infrastructure - seabed mapping and characterisation for environmental management - marine biodiversity surrogacy research - assessment of renewable energy potential **Paleontology** Paleontologists are interested in fossils and how ancient organisms lived. **Paleontology** is the study of fossils and what they reveal about the history of our planet. In marine environments, microfossils collected within layers of sediment cores provide a rich source of information about the environmental history of an area. **Sedimentology** Sedimentology is the study of sediment grains in marine and other deposits, with a focus on physical properties and the processes which form a deposit. Deposition is a geological process where geological material is added to a landform. Key physical properties of interest include: - the size and shape of sediment grains - the degree of sorting of a deposit - the composition of grains within a deposit - sedimentary structures. These properties together provide a record of the mechanisms active during sediment transportation and deposition which allows the interpretation of the environmental conditions that produced a sediment deposit, either in modern settings or in the geological record. **Additional Branches** - **Benthic Ecology.** Benthic ecology is the study of living things on the seafloor and how they interact with their environment. - **Biostratigraphy. **Biostratigraphy is the branch of stratigraphy that uses fossils to establish relative ages of rock and correlate successions of sedimentary rocks within and between depositional basins. - **Geochronology.** Geochronology is a discipline of geoscience which measures the age of earth materials and provides the temporal framework in which other geoscience data can be interpreted in the context of Earth history. - **Geophysics.** Information relating to various techniques including: airborne electromagnetics, gravity, magnetics, magnetotellurics, radiometrics, rock properties and seismic. - **Marine Geochemistry.** Marine geochemistry is the science used to help develop an understanding of the composition of coastal and marine water and sediments. - **Marine Geophysics.** Marine geophysics is a scientific discipline which uses the quantitative observation of physical properties to understand the seafloor and sub-seafloor geology. - **Marine Surveying.** The survey environment varies from oceanographic studies in the water column to investigating sediment and geochemical processes on the seafloor and imaging the sub-seafloor rocks. Surveys are carried over Australia's entire marine jurisdiction, from coastal estuaries and bays, across the continental shelf and slope, to the deep abyssal plains. - **Spectral Geology.** Spectral geology is the measurement and analysis of portions of the electromagnetic spectrum to identify spectrally distinct and physically significant features of different rock types and surface materials, their mineralogy and their alteration signatures. The Nature of Science --------------------- Sometime in your life you've asked a question about the world around you. Probably you've asked a lot of questions over the years. The best way to answer questions about the natural world is by using** science**. Scientists ask questions every day, and then use a set of steps to answer those questions. The steps are known as the scientific method. By following the scientific method, scientists come up with the best information about the natural world. As a scientist, you need to do experiments to find out about the world. You also need to wonder, observe, talk, and think. Everything we learn helps us to ask new and better questions. Scientific Method ----------------- The **scientific method** is a set of steps that help us to answer questions. When we use logical steps and control the number of things that can be changed, we get better answers. As we test our ideas, we may come up with more questions. The basic sequence of steps followed in the scientific method is illustrated in figure 1.  Figure 1. The Scientific Method ### **Questions** A field that has recently been harvested; one portion has sunk down giving way to ground water. Figure 2. Soil is often lost from ground that has been plowed. Asking a question is one really good way to begin to learn about the natural world. You might have seen something that makes you curious. You might want to know what to change to produce a better result. Let's say a farmer is having an erosion problem. She wants to keep more soil on her farm. The farmer learns that a farming method called "no-till farming" allows farmers to plant seeds without plowing the land. She wonders if planting seeds without plowing will reduce the erosion problem and help keep more soil on her farmland. Her question is this: "Will using the no-till method of farming help me to lose less soil on my farm?" (figure 2). ### **Research**  Figure 3. Rather than breaking up soil like in this picture, the farmer could try no-till farming methods. Before she begins, the farmer needs to learn more about this farming method. She can look up information in books and magazines in the library. She may also search the Internet. A good way for her to learn is to talk to people who have tried this way of farming. She can use all of this information to figure out how she is going to test her question about no-till farming. Farming machines are shown in the figure 3. ### **Hypothesis** After doing the research, the farmer will try to answer the question. She might think, "If I don't plow my fields, I will lose less soil than if I do plow the fields. Plowing disrupts the soil and breaks up roots that help hold soil in place." This answer to her question is a **hypothesis**. A hypothesis is a reasonable explanation. A hypothesis can be tested. It may be the right answer, it may be a wrong answer, but it must be testable. Once she has a hypothesis, the next step is to do experiments to test the hypothesis. A hypothesis can be proved or disproved by testing. If a hypothesis is repeatedly tested and shown to be true, then scientists call it a **theory**. ### **Experiment** When we design experiments, we choose just one thing to change. The thing we change is called the **independent variable**. In the example, the farmer chooses two fields and then changes only one thing between them. She changes how she plows her fields. One field will be tilled and one will not. Everything else will be the same on both fields: the type of crop she grows, the amount of water and fertilizer that she uses, and the slope of the fields she plants on. The fields should be facing the same direction to get about the same amount of sunlight. These are the experimental **controls**. If the farmer only changes how she plows her fields, she can see the impact of the one change. After the experiment is complete, scientists then measure the result. The farmer measures how much soil is lost from each field. This is the **dependent variable**. How much soil is lost from each field "depends" on the plowing method. ### **Data and Experimental Error** Figure 4. A pair of farmers take careful measurements in the field. Figure 4. A pair of farmers take careful measurements in the field. During an experiment, a scientist collects data. The data might be measurements, like the farmer is taking in figure 4. The scientist should record the data in a notebook or onto a computer. The data is kept in charts that are clearly labeled. Labeling helps the scientist to know what each number represents. A scientist may also write descriptions of what happened during the experiment. At the end of the experiment the scientist studies the data. The scientist may create a graph or drawing to show the data. If the scientist can picture the data the results may be easier to understand. Then it is easier to draw logical conclusions. Even if the scientist is really careful it is possible to make a mistake. One kind of mistake is with the equipment. For example, an electronic balance may always measure one gram high. To fix this, the balance should be adjusted. If it can't be adjusted, each measurement should be corrected. A mistake can come if a measurement is hard to make. For example, the scientist may stop a stopwatch too soon or too late. To fix this, the scientist should run the experiment many times and make many measurements. The average of the measurements will be the accurate answer. Sometimes the result from one experiment is very different from the other results. If one data point is really different, it may be thrown out. It is likely a mistake was made in that experiment. ### **Conclusions** The scientist must next form a conclusion. The scientist must study all of the data. What statement best explains the data? Did the experiment prove the hypothesis? Sometimes an experiment shows that a hypothesis is correct. Other times the data disproves the hypothesis. Sometimes it's not possible to tell. If there is no conclusion, the scientist may test the hypothesis again. This time he will use some different experiments. No matter what the experiment shows the scientist has learned something. Even a disproved hypothesis can lead to new questions. The farmer grows crops on the two fields for a season. She finds that 2.2 times as much soil was lost on the plowed field as compared to the unplowed field. She concludes that her hypothesis was correct. The farmer also notices some other differences in the two plots. The plants in the no-till plots are taller. The soil moisture seems higher. She decides to repeat the experiment. This time she will measure soil moisture, plant growth, and the total amount of water the plants consume. From now on she will use no-till methods of farming. She will also research other factors that may reduce soil erosion. ### **Theory** When scientists have the data and conclusions, they write a paper. They publish their paper in a scientific journal. A journal is a magazine for the scientists who are interested in a certain field. Before the paper is printed, other scientists look at it to try to find mistakes. They see if the conclusions follow from the data. This is called peer review. If the paper is sound it is printed in the journal. Other papers are published on the same topic in the journal. The evidence for or against a hypothesis is discussed by many scientists. Sometimes a hypothesis is repeatedly shown to be true and never shown to be false. The hypothesis then becomes a theory. Sometimes people say they have a "theory" when what they have is a hypothesis. In science, a theory has been repeatedly shown to be true. A theory is supported by many observations. However, a theory may be disproved if conflicting data is discovered. Many important theories have been shown to be true by many observations and experiments and are extremely unlikely to be disproved. These include the theory of plate tectonics and the theory of evolution. **[Geologic Tools]** Geologists use a lot of tools to aid their studies. Some of the most common tools used are compasses, rock hammers, hand lenses, and field books. **Compasses** There are a number of different (specialised) magnetic compasses used by geologists to measure orientation of geological structures, as they map in the field, to analyse (and document) the geometry of bedding planes, joints, and/or metamorphic foliations and lineations.[^\[1\]^](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#footnote-1709-1) In this aspect the most common device used to date is the analogue compass. **Classic geological compasses** Classic geological compasses that are of practical use combine two functions, direction finding and navigation (especially in remote areas), and the ability to measure strike and dip of bedding surfaces and/or metamorphic foliation planes. Structural geologists (i.e. those concerned with geometry and the pattern of relative movement) also have a need to measure the plunge and plunge direction of lineations. Compasses in common use include the Brunton compass and the Silva compass. **Modern Geological Compasses** The concept of modern geological compass was developed by Eberhard Clar of the University of Vienna during his work as structural geologist. He published it in 1954.[^\[2\]^](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#footnote-1709-2) An advantage of his concept is that strike and dip is measured in one step, using the vertical circle for dip angle and the compass for the strike direction. The first implementation was done by the VEB Freiberger Präzisionsmechanik in Freiberg, Germany. The details of the design were made in a close cooperation with the Freiberg University of Mining and Technology.[^\[3\]^](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#footnote-1709-3) +-----------------------+-----------------------+-----------------------+ | top | | | | view of | | | | compass | | | | | | | | Setup of a modern | | | | geological compass | | | | after Prof. Clar | | | | (Freiberger), total | | | | view | | | +-----------------------+-----------------------+-----------------------+ **Usage** Strike line and dip of a plane describing attitude relative to a horizontal plane and a vertical plane perpendicular to the strike line Figure: Strike line and dip of a plane describing attitude relative to a horizontal plane and a vertical plane perpendicular to the strike line At first sight it appears confusing to the novice user, for the numbers on the compass dial ascend in an anticlockwise direction. This is because the compass is used to determine dip and dip-direction of surfaces (foliations), and plunge and plunge-direction of lines (lineations). To use the compass one aligns the lid of the compass with the orientation of the surface to be measured (to obtain dip and dip direction), or the edge of the lid of the compass with the orientation of the line (to obtain plunge and plunge direction). The compass must be twisted so that the base of the compass becomes horizontal, as accomplished using the spirit level incorporated in it. The needle of the compass is then freed by using the side button, and allowed to spin until the damping action slows its movement, and then stabilises. The side button is released and the needle is then firmly held in place, allowing the user thereafter to conveniently read the orientation measured. One first reads the scale that shows the angle subtended by the lid of the compass, and then depending on the colour shown (red or black) the end of the compass needle with the corresponding colour. Data are then recorded as (for example) 25°-\>333° (dip and dip-direction) or (plunge and plunge-direction). This compass has the most use by structural geologists, measuring foliation and lineation in metamorphic rocks, or faults and joints in mining areas. **Digital Compasses** With the advent of the smartphone, geological compass programs based on the 3-axis teslameter and the 3-axis accelerometer have also begun to appear. These compass programs use vector algebra to compute plane and lineation orientations from the accelerometer and magnetometer data, and permit rapid collection of many measurements. However, some problems are potentially present. Smartphones produce a strong magnetic field of their own which must be compensated by software; as well, because the Earth's magnetic field fluctuates rapidly, measurements made by smartphone geological compasses can potentially be susceptible to considerable noise. Users of a smartphone compass should carefully calibrate their devices and run several tests against traditional magnetic compasses in order to understand the limitations of their chosen program. **Rock Hammers**  Figure: A geologist's hammer used to break up rocks, as well as a scale in the photograph A **geologist's hammer**, **rock hammer**, **rock pick**, or **geological pick** is a hammer used for splitting and breaking rocks. In field geology, they are used to obtain a fresh surface of a rock to determine its composition, nature, mineralogy, history, and field estimate of rock strength. In fossil and mineral collecting, they are employed to break rocks with the aim of revealing fossils inside. Geologist's hammers are also sometimes used for scale in a photograph. **Shape** Geologist's hammers, as with most hammers, have two heads, one on either side. Most commonly, the tool consists of a flat head on one end, with either a chisel or a pick head at the other end.[^\[4\]^](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#footnote-1709-4) - A chisel head (pictured), which is shaped like a chisel, is useful for clearing covering vegetation from exposures and is sometimes (though inadvisedly) used to pry open fissures. Some rocks can be easily split, like slate or shale, to reveal any fossils. - A pick head, which terminates in a sharp point to deliver maximum pressure, is often preferred for harder rocks. A geologist's hammer bearing a pick end is often referred to as a rock pick or geological pick instead of a geologist's hammer. - A flat head is used to deliver a blow to a rock with the intention of splitting it. Specimens or samples can be trimmed to remove sharp corners or reduce them in size. **Construction** A geologist\'s hammer with tubular shaft and chisel head A geologist's hammer with tubular shaft and chisel head The effective power of a geologist's hammer is mainly considered to be a reflection of its head weight and handle length. Head weight may range from 8 oz (225 g) or less on a small hammer---such as would generally be used for casual use or by children---to 24 oz (680 g) and greater. A hammer of 16 oz (450 g) is often quoted as sufficient for all rock types, although metamorphic or igneous rocks often require heavier hammers for a more powerful blow. The best geologist's hammers are forged from one piece of hardened steel, which renders them sturdy and long-lasting. Alternatives such as tubular- and wooden-shafted hammers are more commonly used, in part due to their lower cost. Such alternative handles sacrifice strength and make the hammer unsuitable for high-strain activities such as prying. The form and weighting of the shaft defines the balance, which itself defines the ease, efficiency, and comfort of use of the geologist's hammer. **Hand Lenses**  Loupe used by a geologist The hand lens is a vital geological field tool used to identify small mineral crystals and structures in rocks. It is a simple, small magnification device used to see small details more closely. Unlike a magnifying glass, a loupe does not have an attached handle, and its focusing lens(es) are contained in an opaque cylinder or cone or fold into an enclosing housing that protects the lenses when not in use. Three basic types of hand lenses exist: - Simple lenses, which result in the highest degree of optical aberration and are generally lower magnification. - Multiple lenses, generally higher magnification because of the reduced optical aberration. - Prismatic, Multiple lenses with prisms used to change the perspective. Jewelers typically use a monocular, handheld loupe in order to magnify gemstones and other jewelry that they wish to inspect.[^\[5\]^](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#footnote-1709-5) A 10x magnification is good to use for inspecting jewelry and hallmarks[^\[6\]^](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#footnote-1709-6) and is the Gemological Institute of America's standard for grading diamond clarity. Stones will sometimes be inspected at higher magnifications than 10x, although the depth of field, which is the area in focus, becomes too small to be instructive.[^\[7\]^](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#footnote-1709-7) The accepted standard for grading diamonds is therefore that inclusions and blemishes visible at 10x impact the clarity grade.[^\[8\]^](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#footnote-1709-8) **Field Books** **Field books** are used to take fieldnotes; they can be anything from a composition type notebook to a spiral, but most use [an actual "field book" like those available for purchase here](http://www.tigersupplies.com/Products/Sokkia-Transit-Field-Book__SOK815200.aspx?gclid=CO-e7qCm6cwCFVclgQodoDABlQ). **Fieldnotes** refer to qualitative notes recorded by scientists during or after their observation of a specific phenomenon they are studying. They are intended to be read as evidence that gives meaning and aids in the understanding of the phenomenon. Fieldnotes allow the researcher to access the subject and record what they observe in an unobtrusive manner. One major disadvantage of taking fieldnotes is that they are recorded by an observer and are thus subject to (a) memory[^\[9\]^](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#footnote-1709-9) and (b) possibly, the conscious or unconscious bias of the observer. It is best to record fieldnotes immediately after leaving the site to avoid forgetting important details. Fieldnotes are particularly valued in  geology and other descriptive sciences such as ethnography, biology, and archaeology. **Structure** There are two components of fieldnotes: descriptive information and reflective information.[^\[10\]^](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#footnote-1709-10) - Descriptive information is factual data that is being recorded. Factual data includes time and date, the state of the physical setting, social environment, descriptions of the subjects being studied and their roles in the setting, and the impact that the observer may have had on the environment.[^\[11\]^](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#footnote-1709-11) - Reflective information is the observer's reflections about the observation being conducted. These reflections are ideas, questions, concerns, and other related thoughts.[^\[12\]^](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#footnote-1709-12) Fieldnotes can also include sketches, diagrams, and other drawings. Visually capturing a phenomenon requires the observer to pay more attention to every detail as to not overlook anything.[^\[13\]^](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#footnote-1709-13) 1. *The Mapping of Geological Structures* (Geological Society of London Handbook Series) \[Paperback\] K. R. McClay; *Statistics of Earth Science Data: Their Distribution in Time, Space and Orientation* \[Paperback\] Graham J. Borradaile (Author) [↵](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#return-footnote-1709-1) 2. Clar, E.: *A dual-circle geologist's and miner's compass for the measurement of areal and linear geological elements.* Separate print from the negotiations of the Federal Institute of Geology Vienna, 1954, vol. 4 [↵](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#return-footnote-1709-2) 3. \"Geologist\'s Compass: Operating Manual,\" *Freiberger Präzisionsmechanik*. . [↵](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#return-footnote-1709-3) 4. MartinS (2006). [\"\'Geological Hammers\' info page\"](http://martins.googlepages.com/geologicalhammers) [↵](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#return-footnote-1709-4) 5. [\"Jewelry - How to Use a Loupe - Using Jewelry Magnifiers\"](http://jewelry.about.com/od/jewelryappraisal/ss/loupe.htm). Jewelry.About.com [↵](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#return-footnote-1709-5) 6. *Ibid*. [↵](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#return-footnote-1709-6) 7.  [↵](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#return-footnote-1709-7) 8. [\"The 4C\'s Of Diamonds: Diamond Clarity\"](http://www.leibish.com/diamond-clarity-article-483). Leibish & Co. [↵](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#return-footnote-1709-8) 9. Canfield, Michael (2011). *Field Notes on Science & Nature*. Harvard University Pres. p. 21. [↵](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#return-footnote-1709-9) 10. Labaree, Robert V. [\"Research Guides: Organizing Your Social Sciences Research Paper: Writing Field Notes\"](http://libguides.usc.edu/writingguide/fieldnotes). *libguides.usc.edu*. Retrieved 2016-04-12. [↵](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#return-footnote-1709-10) 11. *Ibid*. [↵](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#return-footnote-1709-11) 12. *Ibid*. [↵](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#return-footnote-1709-12) 13. Canfield,Michael (2011). *Field Notes on Science & Nature*. p. 162. [↵](https://courses.lumenlearning.com/geo/chapter/reading-geologic-tools/#return-footnote-1709-13) **Maps** Maps are essential tools in geology. Maps are as important in geology as written texts are in the study of literature. By studying maps, a geologist can see the shape and geology of the earth's surface and deduce the geological structures that lie hidden beneath the surface. Geologists are trained in map reading and map making. Many geologists have experience mapping some part of the earth's surface. It takes some training to read maps skillfully. You are not expected to become a geological expert in reading maps. However, you will be expected to develop your map reading skills as you use maps to help you learn geology. **Topographic Maps** A complex map of Yellowstone. There are several natural features on the map, including springs, geysers, and plains. Figure 1. Map of Yellowstone. A **topographic map** (like the one in figure 1) is one type of map used by geologists. Topographic maps show the three-dimensional shape of the land and features on the surface of the earth. Topographic maps are also used by hikers, planners who make decisions on zoning and construction permits, government agencies involved in land use planning and hazard assessments, and civil engineers. The topographic maps drawn and published by the U. S. Geological Survey portray the grids that are used on deeds to identify the location of real estate, so homeowners and property owners sometimes find it useful to refer to topographic maps of their area. Most topographic maps make use of **contour lines** to depict elevations above sea level. The contour lines reveal the shape of the land in the vertical direction, allowing the 3-dimensional shape of the land to be portrayed on a 2-dimensional sheet of paper or computer screen. When you know how to read contour lines, you can look at them on a topographic map and visualize the mountains, plains, ridges, or valleys that they portrays. Topographic maps are important in geology because they portray the surface of the earth in detail. This view of the surface shows patterns that provide information about the geology beneath the surface. The landforms of the earth result from surface processes such as erosion or sedimentation combined with internal geological processes such as magma rising to create a volcano or a ridge of bedrock pushed up along a fault. By studying the shape of the earth's surface through topographic maps, geologists can understand the nature of surface processes in a given area, including zones subjected to landsliding, places undergoing erosion and places where sediment is accumulating. They can also find clues to the underlying geologic structure and geologic history of the area. In addition to a topographic map, a complete understanding of the underlying geologic structure and history of an area requires completion of a geologic map and cross-sections. A topographic map provides the frame of reference upon which most geologic maps are constructed. **Bathymetric Maps**  Figure 3. Loihi volcano growing on the flank of Kilauea volcano in Hawaii. Black lines in the inset show the land surface above sea level and blue lines show the topography below sea level. Click on the image to view a larger version. A **bathymetric map** is like a topographic map with the contour lines representing depth below sea level, rather than height above. Numbers are low near sea level and become higher with depth. Kilauea is the youngest volcano found above sea level in Hawaii. On the flank of Kilauea is an even younger volcano called Loihi. The bathymetric map pictured in figure 3 shows the form of Loihi. **Geologic Maps** A **geologic map** shows the geological features of a region (see figure 4 for an example). Rock units are color-coded and identified in a key. Faults and folds are also shown on geologic maps. The geology is superimposed on a topographic map to give a more complete view of the geology of the region. A geologic map shows mappable rock units, mappable sediment units that cover up the rocks, and geologic structures such as faults and folds. A mappable unit of rock or sediment is one that a geologist can consistently recognize, trace across a landscape, and describe so that other people are able to recognize it and verify its presence and identity. Mappable units are shown as different colors or patterns on a base map of the geographic area. geologic map of the region around Old Faithful, Yellowstone National Park Figure 4. A geologic map of the region around Old Faithful, Yellowstone National Park. Geologic maps are important for two reasons. First, as geologists make geologic maps and related explanations and cross-sections, they develop a theoretical understanding of the geology and geologic history of a given area. Second, geologic maps are essential tools for practical applications such as zoning, civil engineering, and hazard assessment. Geologic maps are also vital in finding and developing geological resources, such as gravel to help build the road you drive on, oil to power the car you travel in, or aluminum to build the more fuel-efficient engine in your next vehicle. Another resource that is developed on the basis of geologic maps is groundwater, which many cities, farms, and factories rely on for the water they use. **Essential Components of Geologic Maps** A complete geologic map has at least two features: - the map itself - the map legend or key that explains all the symbols on the map. Professional geologic maps usually have two other components as well: - an accompanying explanation of the rock or sediment units - geologic cross-sections of the map area. The legend or key to a geologic map is usually printed on the same page as the map and follows a customary format. The symbol for each rock or sediment unit is shown in a box next to its name and brief description. These symbols are stacked in age sequence from oldest at the bottom to youngest at the top. The geologic era, or period, or epoch--the geologic age--is listed for each rock unit in the key. By stacking the units in age sequence from youngest at the top to oldest at the bottom, and identifying which interval of geologic time each unit belongs to, the map reader can quickly see the age of each rock or sediment unit. The map key also contains a listing and explanation of the symbols shown on the map, such as the symbols for different types of faults and folds. See the Table of Geologic Map Symbols for pictures and an overview of the map symbols, including strikes and dips, faults, folds, and an overview. **Geologic Cross-Sections** **A geologic cross-section is a sideways view of a slice of the earth. It shows how the different types of rock are layered or otherwise configured, and it portrays geologic structures beneath the earth's surface, such as faults and folds. Geologic cross-sections are constructed on the basis of the geology mapped at the surface combined with an understanding of rocks in terms of physical behavior and three-dimensional structures.** **Summary** - Earth scientists regularly use topographic, bathymetric, and geologic maps. - Topographic maps reveal the shape of a landscape. Elevations indicate height above sea level. - Bathymetric maps are like topographic maps of features found below the water. Elevations indicate depth below sea level. - Geologic maps show rock units and geologic features like faults and folds. **[Location and Direction]** **If you found this feature while out in the field, could you find it again?**  Figure 1. Old Faithful If you're going to make observations of geological features, you're going to need to know the location where you are so you can mark it on a map. If you find a rock formation filled with gold, you'll want to be able to find the location again! You may need to tell someone when your truck gets stuck when you're in the field so you'll need a direction to give them. The photo in figure 1 is of Old Faithful Geyser in Yellowstone National Park. Let's explore just a few of the ways we can pinpoint the location of this famous geological icon. **Location** How would you find Old Faithful? One way is by using latitude and longitude. Any **location** on Earth's surface --- or on a map --- can be described using these coordinates. Latitude and longitude are expressed as degrees that are divided into 60 minutes. Each minute is divided into 60 seconds. **Latitude** A look on a reliable website shows us that Old Faithful Geyser is located at N44^o^27' 43''. What does this mean? **Latitude** tells the distance north or south of the Equator. Latitude lines start at the Equator and circle around the planet. The North Pole is 90^o^N, with 90 degree lines in the Northern Hemisphere. Old Faithful is at 44 degrees, 27 minutes and 43 seconds north of the Equator. That's just about exactly half way between the Equator and the North Pole! **Longitude** The latitude mentioned above does not locate Old Faithful exactly, since a circle could be drawn that latitude north of the Equator. To locate Old Faithful we need another point -- longitude. At Old Faithful the longitude is W110^o^49'57''. **Longitude** lines are circles that go around the Earth from north to south, like the sections of an orange. Longitude is measured perpendicular to the Equator. The Prime Meridian is 0^o^ longitude and passes through Greenwich, England. The International Date Line is the 180^o^ meridian. Old Faithful is in the Western Hemisphere, between the Prime Meridian in the east and the International Date Line in the west. **Elevation** An accurate location must take into account the third dimension. **Elevation** is the height above or below sea level. **Sea level** is the average height of the ocean's surface or the midpoint between high and low tide. Sea level is the same all around Earth. Old Faithful is higher above sea level than most locations at 7,349 ft (2240 m). Of course, the highest point on Earth, Mount Everest, is much higher at 29,029 ft (8848 m). **Global Positioning System** Satellites continually orbit Earth and can be used to indicate location. A **global positioning system** receiver detects radio signals from at least four nearby GPS satellites. The receiver measures the time it takes for radio signals to travel from a satellite and then calculates its distance from the satellite using the speed of radio signals. By calculating distances from each of the four satellites the receiver can triangulate to determine its location. You can use a GPS meter to tell you how to get to Old Faithful. **Direction** Direction is important if you want to go between two places. **Directions** are expressed as north (N), east (E), south (S), and west (W), with gradations in between. The most common way to describe direction in relation to the Earth's surface is with a **compass**, a device with a floating needle that is actually a small magnet. The compass needle aligns itself with the Earth's magnetic north pole. Since the magnetic north pole is 11.5 degrees offset from its geographic north pole on the axis of rotation, you must correct for this discrepancy. Without using a compass, we can say that to get to Old Faithful, you enter Yellowstone National Park at the South Entrance, drive north-northeast to West Thumb, and then drive west-northwest to Old Faithful. **Summary** - Latitude is the distance north or south of the Equator and is expressed as a number between 0 and 90 degrees north or south. - Longitude is the distance east or west of the Prime Meridian and is expressed as a number between 0 and 180 degrees east or west. - Elevation is the height above sea level. - Direction is expressed as north, south, east, or west, or some gradation between them. ** [Scientific Models]** Scientists use models to help them understand and explain ideas. Models explain objects or systems in a more simple way. Models often only show only a part of a system. The real situation is more complicated. Models help scientists to make predictions about complex systems. Some models are something that you can see or touch. Other types of models use an idea or numbers. Each type is useful in certain ways. Scientists create models with computers. Computers can handle enormous amounts of data. This can more accurately represent the real situation. For example, Earth's climate depends on an enormous number of factors. Climate models can predict how climate will change as certain gases are added to the atmosphere. To test how good a model is, scientists might start a test run at a time in the past. If the model can predict the present it is probably a good model. It is more likely to be accurate when predicting the future. **[Physical Models]** A **physical model** is a representation of something using objects. It can be three-dimensional, like a globe. It can also be a two-dimensional drawing or diagram. Models are usually smaller and simpler than the real object. They most likely leave out some parts, but contain the important parts. In a good model the parts are made or drawn to scale. Physical models allow us to see, feel and move their parts. This allows us to better understand the real system. An example of a physical model is a drawing of the layers of Earth (figure 1). A drawing helps us to understand the structure of the planet. Yet there are many differences between a drawing and the real thing. The size of a model is much smaller, for example. A drawing also doesn't give good idea of how substances move. Arrows showing the direction the material moves can help. A physical model is very useful but it can't explain the real Earth perfectly. Diagram showing the different layers of the earth. From the outside to the inside they are the crust, moho, upper mantle, lower mantle, D(double prime)-layer, outer core, liquid-solid boundary, and inner core. Figure 1. Earth's Center. **Ideas as Models**  Figure 2. A collision showing a meteor striking Earth. Some models are based on an idea that helps scientists explain something. A good idea explains all the known facts. An example is how Earth got its Moon. A Mars-sized planet hit Earth and rocky material broke off of both bodies (figure 2). This material orbited Earth and then came together to form the Moon. This is a model of something that happened billions of years ago. It brings together many facts known from our studies of the Moon's surface. It accounts for the chemical makeup of rocks from the Moon, Earth, and meteorites. The physical properties of Earth and Moon figure in as well. Not all known data fits this model, but much does. There is also more information that we simply don't yet know. **Models that Use Numbers** Models may use formulas or equations to describe something. Sometimes math may be the only way to describe it. For example, equations help scientists to explain what happened in the early days of the universe. The universe formed so long ago that math is the only way to describe it. A climate model includes lots of numbers, including temperature readings, ice density, snowfall levels, and humidity. These numbers are put into equations to make a model. The results are used to predict future climate. For example, if there are more clouds, does global temperature go up or down? Models are not perfect because they are simple versions of the real situation. Even so, these models are very useful to scientists. These days, models of complex things are made on computers. **Geologic Modelling** Screenshot of a structure map generated by Contour map software for an 8500ft deep gas & Oil reservoir in the Erath field, Vermilion Parish, Erath, Louisiana. The left-to-right gap, near the top of the contour map indicates a Fault line. This fault line is between the blue/green contour lines and the purple/red/yellow contour lines. The thin red circular contour line in the middle of the map indicates the top of the oil reservoir. Because gas floats above oil, the thin red contour line marks the gas/oil contact zone. Figure 1. Geological mapping software displaying a screenshot of a structure map generated for an 8500ft deep gas & Oil reservoir in the Erath field, Vermilion Parish, Erath, Louisiana. The left-to-right gap, near the top of the contour map indicates a Fault line. This fault line is between the blue/green contour lines and the purple/red/yellow contour lines. The thin red circular contour line in the middle of the map indicates the top of the oil reservoir. Because gas floats above oil, the thin red contour line marks the gas/oil contact zone. **Geologic modelling**, or **Geomodelling**, is the applied science of creating computerized representations of portions of the Earth's crust based on geophysical and geological observations made on and below the Earth surface. A Geomodel is the numerical equivalent of a three-dimensional geological map complemented by a description of physical quantities in the domain of interest. Geomodelling is related to the concept of Shared Earth Model; which is a multidisciplinary, interoperable and updatable knowledge base about the subsurface. Geomodelling is commonly used for managing natural resources, identifying natural hazards, and quantifying geological processes, with main applications to oil and gas fields, groundwater aquifers and ore deposits. For example, in the oil and gas industry, realistic geologic models are required as input to reservoir simulator programs, which predict the behavior of the rocks under various hydrocarbon recovery scenarios. A reservoir can only be developed and produced once; therefore, making a mistake by selecting a site with poor conditions for development is tragic and wasteful. Using geological models and reservoir simulation allows reservoir engineers to identify which recovery options offer the safest and most economic, efficient, and effective development plan for a particular reservoir. Geologic modelling is a relatively recent subdiscipline of geology which integrates structural geology, sedimentology, stratigraphy, paleoclimatology, and diagenesis; In 2-dimensions (2D), a geologic formation or unit is represented by a polygon, which can be bounded by faults, unconformities or by its lateral extent, or crop. In geological models a geological unit is bounded by 3-dimensional (3D) triangulated or gridded surfaces. The equivalent to the mapped polygon is the fully enclosed geological unit, using a triangulated mesh. For the purpose of property or fluid modelling these volumes can be separated further into an array of cells, often referred to as voxels (volumetric elements). These 3D grids are the equivalent to 2D grids used to express properties of single surfaces. Geomodelling generally involves the following steps: 1. Preliminary analysis of geological context of the domain of study. 2. Interpretation of available data and observations as point sets or polygonal lines (e.g. "fault sticks" corresponding to faults on a vertical seismic section). 3. Construction of a structural model describing the main rock boundaries (horizons, unconformities, intrusions, faults) 4. Definition of a three-dimensional mesh honoring the structural model to support volumetric representation of heterogeneity (see Geostatistics) and solving the Partial Differential Equations which govern physical processes in the subsurface (e.g. seismic wave propagation, fluid transport in porous media). **Geologic modelling components** **Structural framework** Incorporating the spatial positions of the major formation boundaries, including the effects of faulting, folding, and erosion (unconformities). The major stratigraphic divisions are further subdivided into layers of cells with differing geometries with relation to the bounding surfaces (parallel to top, parallel to base, proportional). Maximum cell dimensions are dictated by the minimum sizes of the features to be resolved (everyday example: On a digital map of a city, the location of a city park might be adequately resolved by one big green pixel, but to define the locations of the basketball court, the baseball field, and the pool, much smaller pixels -- higher resolution -- need to be used). **Rock type** Each cell in the model is assigned a rock type. In a coastal clastic environment, these might be beach sand, high water energy marine upper shoreface sand, intermediate water energy marine lower shoreface sand, and deeper low energy marine silt and shale. The distribution of these rock types within the model is controlled by several methods, including map boundary polygons, rock type probability maps, or statistically emplaced based on sufficiently closely spaced well data. **Reservoir quality** Reservoir quality parameters almost always include porosity and permeability, but may include measures of clay content, cementation factors, and other factors that affect the storage and deliverability of fluids contained in the pores of those rocks. Geostatistical techniques are most often used to populate the cells with porosity and permeability values that are appropriate for the rock type of each cell. **Fluid saturation**  Figure 2. A 3D finite difference grid used in MODFLOW for simulating groundwater flow in an aquifer. Most rock is completely saturated with groundwater. Sometimes, under the right conditions, some of the pore space in the rock is occupied by other liquids or gases. In the energy industry, oil and natural gas are the fluids most commonly being modelled. The preferred methods for calculating hydrocarbon saturations in a geologic model incorporate an estimate of pore throat size, the densities of the fluids, and the height of the cell above the water contact, since these factors exert the strongest influence on capillary action, which ultimately controls fluid saturations. **Geostatistics** An important part of geologic modelling is related to geostatistics. In order to represent the observed data, often not on regular grids, we have to use certain interpolation techniques. The most widely used technique is kriging which uses the spatial correlation among data and intends to construct the interpolation via semi-variograms. To reproduce more realistic spatial variability and help assess spatial uncertainty between data, geostatistical simulation based on variograms, training images, or parametric geological objects is often used. **Mineral Deposits** Geologists involved in mining and mineral exploration use geologic modelling to determine the geometry and placement of mineral deposits in the subsurface of the earth. Geologic models help define the volume and concentration of minerals, to which economic constraints are applied to determine the economic value of the mineralization. Mineral deposits that are deemed to be economic may be developed into a mine. **Technology** Geomodelling and CAD share a lot of common technologies. Software is usually implemented using object-oriented programming technologies in C++, Java or C\# on one or multiple computer platforms. The graphical user interface generally consists of one or several 3D and 2D graphics windows to visualize spatial data, interpretations and modelling output. Such visualization is generally achieved by exploiting graphics hardware. User interaction is mostly performed through mouse and keyboard, although 3D pointing devices and immersive environments may be used in some specific cases. GIS (Geographic Information System) is also a widely used tool to manipulate geological data. Geometric objects are represented with parametric curves and surfaces or discrete models such as polygonal meshes. Gravity Highs over the Mardin Uplift Figure 3. Gravity Highs **Research in Geomodelling** Problems pertainting to Geomodelling cover - Defining an appropriate Ontology to describe geological objects at various scales of interest - Integrating diverse types of observations into 3D geomodels: geological mapping data, borehole data and interpretations, seismic images and interpretations, potential field data, well test data, etc. - Better accounting for geological processes during model building - Characterizing uncertainty about the geomodels to help assess risk. Therefore, Geomodelling has a close connection to Geostatistics and Inverse problem theory - Applying of the recent developed Multiple Point Geostatistical Simulations (MPS) for integrating different data sources - Automated geometry optimization and topology conservation **History** In the 1970s, geomodelling mainly consisted of automatic 2D cartographic techniques such as contouring, implemented as FORTRAN routines communicating directly with plotting hardware. The advent of workstations with 3D graphics capabilities during the 1980s gave birth to a new generation of geomodelling software with graphical user interface which became mature during the 1990s. Since its inception, geomodelling has been mainly motivated and supported by oil and gas industry. **Geologic modelling software** Software developers have built several packages for geologic modelling purposes. Such software can display, edit, digitise and automatically calculate the parameters required by engineers, geologists and surveyors. Current software is mainly developed and commercialized by oil and gas or mining industry software vendors: **Geologic modelling and visualisation** - - SGS Genesis - IRAP RMS Suite - Geomodeller3D - Geosoft provides GM-SYS and VOXI 3D modelling software - GSI3D - Petrel - Rockworks - - Move **Groundwater modelling** - FEFLOW - FEHM - MODFLOW - GMS - Visual MODFLOW - ZOOMQ3D Moreover, industry Consortia or companies are specifically working at improving standardization and interoperability of earth science databases and geomodelling software: - Standardization: GeoSciML by the Commission for the Management and Application of Geoscience Information, of the International Union of Geological Sciences. - Standardization: RESQML(tm) by Energistics - Interoperability: OpenSpirit, by TIBCO(r) Putting It Together: Science of Geology --------------------------------------- Summary ------- In this section, you learned the following: 1. The extensive definition of geology 2. The various fields within geology and what they study 3. How scientists use the scientific method to answer questions Synthesis --------- While we have not thoroughly answered our questions from the beginning of the outcome, we should be able to understand the connection these questions have to geology. We now know that geology is more than rocks---it deals with the resources we use in our everyday life, and it explains why some areas are more tectonically active than others. As we move through the course, keep these questions in mind. So let's get started on this course and see why geology *rocks*.