1 Understanding Science

It is a steep rock jutting out of the countryside.
Devils Tower, Wyoming.

1 Understanding Science


At the end of this chapter, students should be able to:

  • Contrast objective vs. subjective observations and quantitative vs qualitative observations.
  • Identify a pseudoscience based on its falsifiability.
  • Contrast how Aristotle and Galileo reached conclusions about the natural environment.
  • Explain and apply the scientific method.
  • Describe and apply the foundations of modern geologic thought such as the Principle of Uniformitarianism.
  • Contrast Uniformitarianism with Catastrophism.
  • Explain the importance of studying geology.
  • Identify the rock cycle processes by which earth materials are transformed into each other.
  • Describe what makes a reputable scientific study.
  • Explain the basic rhetorical arguments used by science deniers.

1.1 What is Science?

The waterfall is in a valley
This is Grand Canyon of the Yellowstone in Yellowstone National Park. An objective statement about this would be: “The picture is of a waterfall.” A subjective statement would be: “The picture is beautiful.” An inference would be “The waterfall is there because of erosion.”

Science seeks to understand the fundamental laws and principles that cause natural patterns and govern natural processes. Science is more than just a body of knowledge, science is a way of thinking that provides a means to evaluate and create new knowledge without bias . At its best, science uses objective evidence over subjective evidence to reach sound and logical conclusions. An objective observation is without personal bias and is observed the same by all individuals. Humans, by their nature, do have bias, so no observation is completely free of bias; the goal is to be as free of bias as possible. A subjective observation is based on a person’s feelings and beliefs and is unique to that individual. Science uses quantitative over qualitative objective observations whenever possible. A quantitative observation can be measured and expressed with a number. Qualitative observations are not numeric but rather verbal descriptions. For example, saying a rock is red or heavy is qualitative. But measuring the exact color of red, or measuring the density of the rock (which can be traced to the proportion of certain minerals in the rock) is quantitative. This is why quantitative measurements are much more useful to scientists. Calculations can be done on a specific numbers, but cannot be done on qualitative values.  

A person is looking into the canyon.
Canyons like this, carved in the deposit left by the May 18th, 1980 eruption of Mt. St. Helens, are sometimes used by purveyors of pseudoscience as evidence for the Earth being very young. In reality, the non-lithified volcanic deposit is carved much more easily than other canyons like the Grand Canyon.

Truth in science is a difficult concept, and this is because science is falsifiable, which means an initial explanation (hypothesis) is testable and able to be proven false. A scientific theory can never completely be proven true, it is only after exhaustive attempts to falsify competing ideas and variations that the theory is assumed to be true.  While it may seem like a weakness, the strength behind this is that all scientific ideas have stood up to scrutiny, which is not necessarily true for non-scientific ideas and procedures. In fact, it is the ability to prove current ideas wrong that is a driving force in science, and has driven many scientific careers. Science and scientists are wary of situations which either discourage or avoid the process of falsifiability. If a statement or an explanation of a phenomenon cannot be tested, or does not meet scientific standards, then it is not considered science, but rather is considered a pseudoscience. Falsifiability separates science from pseudoscience. Pseudoscience is a collection of ideas that may appear scientific but does not use the scientific method. An example of pseudoscience is astrology which is a belief system that the movement of celestial bodies influences human behavior. This is not to be confused with astronomy which is the scientific study of celestial bodies and the cosmos. There are many celestial observations associated with astrology, but astrology does not use the scientific method. Conclusions in astrology are not based on evidence and experiments, and its statements are not falsifiable.

Many people are standing around and talking.
Geologists share information by publishing, attending conferences, and even going on field trips, such as this trip to western Utah by the Utah Geological Association in 2009.

Science is also a social process. Scientists share their ideas with peers at conferences for guidance and feedback. A scientist’s research paper and data are rigorously reviewed by many qualified peers before publication. Research results are not allowed to be published by a reputable journal or publishing house until other scientists who are experts in the field have determined that the methods are scientifically sound and the conclusions are reasonable. Science aims to “weed out” misinformation, invalid research results, and wild speculation. Thus, the scientific process is slow, cautious, and conservative. Scientists do not jump to conclusions, but wait until an overwhelming amount of evidence from many independent researchers point to the same conclusion before accepting a scientific concept.

1.1.1 The Scientific Method

The diagram is cyclical.
Diagram of the cyclical nature of the scientific method.
Modern science is based on the scientific method, a semi-formal procedure involving a series of steps that can be summarized as starting with a problem or question, followed by testing of ideas with objective observations and experimentation, interpretation of results, conclusions based on evidence, and publication of the results with peer review. This has a long history in human thought, but was first fully formed by Ibn Alhazen over 1000 years ago .  At the forefront are conclusions based on quality objective evidence, not opinion or hearsay. This procedure is described in more detail below. In addition, the following video summarizes the scientific method (video).

Step One – Observation, Problem, or Research Question: A scientist is curious about something and identifies a problem or research question. This may be an observation of natural phenomena which is not well explained in existing research articles or represents a gap in the scientific community’s collective knowledge. This step involves reading on the topic in the scientific literature to understand previous scientific work. In science, observations are focused on quantitative objective data.

There are 12 images of the horse, at least one has the legs off the ground.
A famous hypothesis: Leland Stanford wanted to know if a horse lifted all 4 legs off the ground during a gallop, since the legs are too fast for the human eye to perceive it. These series of photographs by Eadweard Muybridge proved the horse, in fact, does have all four legs off the ground during the gallop.

Step Two – Hypothesis: Once the problem or question is well defined, the scientist proposes a possible answer to the question in the form of a hypothesis. The hypothesis is a tentative explanation that the scientist establishes before any experimentation. A hypothesis must be specific, falsifiable, and based on the scientist’s understanding of other scientific work. Geologists often apply the concept of multiple-working hypotheses, that is the development of several hypotheses that might explain the phenomena before conducting the experiment or field work. This is particularly useful in geology where there are rarely experimental controls and the geologist may have limited opportunities to visit a field location

The next big advancement in geology, and perhaps the largest in the history of geology, is plate tectonics (see chapter 2 for more details). Dogmatic acceptance of Uniformitarianism also inhibited the progress of this idea, mainly because of the permanency placed on the continents and their positions. Ironically, the movement of plates is slow and steady, and would fit into a uniformitarianism model well. However, much time passed with much scientific resistance before the idea took hold. This happened for several reasons. Firstly, the movement was so slow it was overlooked. Secondly, the best evidence was hidden under the ocean. Finally, there was a large amount of inertia behind accepted theories.

He is an older man in this 1992 image.
J. Tuzo Wilson
While not having a specific founder, it is most commonly attributed to Alfred Wegener, who was the first to compile a large data set in 1912 supporting the idea of continents shifting places over time. He was mostly ignored and ridiculed for his idea, but later workers (starting in earnest the late 1950s) like Marie Tharp, Bruce Heezen, Harry Hess, Laurence Morley, Frederick Vine, Drummond Matthews, Kiyoo Wadati, Hugo Benioff, Robert Coats, and J. Tuzo Wilson, benefiting from advances in sub-sea technologies,  had started to discover, describe, and analyze features like the mid-ocean ridge, alignment of earthquakes, and magnetic striping. Gradually but eventually, a paradigm shift occurred which revolutionized the science of geology into what we know today.

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1.4 Why Study Geology?

The students are on the red rock
A class looks at rocks in Zion National Park.

There are many branches of natural science such as chemistry, physics, biology, astronomy, and others. Like chemistry and physics, geology is a physical science. From Greek , meaning “Earth”, and logos, meaning “to think or reckon with,” geology is the application of the scientific method to learn about Earth’s materials and processes. So why study geology? Geology has an important role in society since its principles are essential to locating, extracting and managing natural resources, evaluating environmental impacts of using or extracting these resources, and as well as understanding and mitigating the effects of natural hazards.

The dam has a large lake behind it
Hoover Dam provides hydroelectric energy and stores water for southern Nevada.

Geology plays a key role in our use of natural resourcesany naturally occurring material that can be extracted from the Earth for economic gain. An economically developed modern society is dependent on many of these resources. Geologists are often involved in extraction of fossil fuel energy resources (i.e. coal and petroleum); metal resources such as copper, aluminum, and iron; and water resources in streams and underground reservoirs inside rocks. Our planet has a finite supply of natural resources. Some are nonrenewable resources (fixed in quantity like petroleum) and consumption depletes them. In contrast, renewable resources can be replaced, for example solar or wind energy and wood from forests.

The power plant has smoke coming from it
Coal power plant in Helper, Utah.

In addition to providing essential material for society’s use, resource extraction can impact our natural  environment by leading to the release of resource byproducts into the air, water, and soil which affect human health and the environment. For example, burning fossil fuels in our cars releases chemicals into the air that are not healthy for humans, especially children, and the environment. Mining activities can release heavy metals such as lead and mercury into soil and waterways by runoff and erosion, potentially impacting human health and the environment. Our choices will have an effect on Earth’s environment for the foreseeable future.

Buildings toppled from liquefaction during a 7.5 magnitude earthquake in Japan.
Buildings toppled from liquefaction during a 7.5 magnitude earthquake in Japan.

Another focus of geology is the study of natural hazards created by geologic processes. A natural hazard is a natural phenomena that is potentially dangerous to human life or property such as earthquakes, floods, and landslides. No place on Earth is completely free of natural hazards. The best way to protect yourself is by learning about the natural hazards in your area and how to prepare for them. Common geologic hazards include landslides, earthquakes, tsunamis, floods, volcanic eruptions, and sea-level rise.

The mountain has a large hole in the center that is filled with the lake.
Oregon’s Crater Lake was formed about 7700 years ago after the eruption of Mount Mazama.

Finally, geology is where other scientific disciplines intersect in the concept known as Earth System Science in which the entire planet is viewed as a combination of systems that interact with each other complexly. In science, a system is a group of objects and processes that interact such as the rock cycle. The study of Earth includes five basic systems (or spheres), the Geosphere (the solid body of the Earth), the Atmosphere (the gas envelope surrounding the Earth), the Hydrosphere (water at and near the surface of the Earth in all its forms), the Cryosphere (frozen water part of Earth), and the Biosphere (life on Earth in all its forms and interactions, including humankind). Earth System Science is the study of how these spheres relate, interact, and change in response to natural cycles and new human-driven forces. Geologic events and processes are not isolated from the world—they shape the world. In this study, scientists use elements of physics, chemistry, biology, meteorology, environmental science, zoology, hydrology, and every other discipline of science. Therefore, this geology course provides a broad introduction to science in general and will often reference other science disciplines.

1.4.1 Rock Cycle

The rock cycle shows how different rock groups are interconnected. Metamorphic rocks can come from adding heat and/or pressure to other metamorphic rock or sedimentary or igneous rocks
Rock cycle showing the five materials (such as igneous rocks and sediment) and the processes by which one changes into another (such as weathering). (Source: Peter Davis)

The most fundamental view of Earth materials is the rock cycle, which presents the major materials that comprise the Earth and describes the processes by which they form and relate to each other. The rock cycle is usually said to begin with hot molten liquid rock called magma or lava. Magma forms under the Earth’s surface in the crust or mantle and erupts on Earth’s surface as lava. When magma or lava cools, it solidifies by a process called crystallization in which minerals grow within the magma or lava. The rock that results from this is an igneous rock from the latin word ignis meaning “fire”.

This grey rock has round circles left by raindrops
Lithified raindrop impressions over wave ripples from Nova Scotia.

Igneous rocks (as well as other types of rocks) on Earth’s surface are exposed to processes of weathering and erosion to produce sediments. Weathering is the physical and chemical breakdown of rocks into smaller fragments and erosion is the removal of those fragments from their original location. Once igneous rocks are broken down and transported, these fragments or grains are considered sediments. Sediments such as gravel, sand, silt, and clay can be transported by water in the form of streams, ice in the form of glaciers, and air in the form of wind. Sediments ultimately come to rest in a process known as deposition. The deposited sediments accumulate in place, often under water such as a shallow marine environment, get buried. Within the burial process, the sediments go through compaction  An experiment at the University of Queensland has been going since 1927. A petroleum product called pitch, which is highly viscous, drips out of a funnel about once per decade. A similar experiment is being observed at Trinity College in Dublin.[/caption]Step Three – Experiment and Hypothesis Revision: The scientist develops an experiment which can either support or refute their hypothesis. Many people think experiments are only done in a lab. However, an experiment can be observing natural processes in the field. An experiment can take many forms, but usually includes the systematic gathering of objective data to test the hypothesis. Scientists interpret the results and determine if the data rejects or supports the proposed hypothesis. During or after the experiment, the hypothesis may be revised and tested again. Finally, if the revised hypothesis holds up under experimentation, the scientist will share the results for scrutiny by experts in the field.

Step Four – Peer Review, Publication, and Replication: Scientists share the results of their research by publishing articles in scientific journals and books, which are technical magazines such as Science and Nature. Before a study can be published, specialists who are experts in that field of science review and scrutinize the study’s methods, data, and results. The peer review process is rigorous, and it is difficult to get studies published. Once published, other scientists might attempt to replicate the results. Under this scrutiny, hypotheses that seemed compelling in one study might be proven false in studies conducted by other scientists. New technology can aid in rejecting once accepted ideas and/or hypotheses. Alternately, the hypothesis might be replicated and supported repeatedly, so that the scientific community may come to accept the hypothesis as supporting evidence builds.

He is a male in a suit.
Wegener later in his life, ca. 1924-1930.
Step Five – Theory Development: When a hypothesis has gained wide scientific acceptance through repeatable and documented experiments, scientists then refer to it as a theory. A theory is the best explanation so far based on the available evidence for a natural process or phenomenon. While a hypothesis is a tentative explanation before the experiment, an idea only becomes a theory after many years of experiments by many independent researchers. For example, the early hypothesis of continental drift, first proposed by Alfred Wegener in 1912, was initially dismissed but after decades of additional evidence from more researchers using more advanced technology, the hypothesis was eventually accepted and revised as the Theory of Plate Tectonics. The Theory of Evolution through Natural Selection is another example. Originating from the work of Charles Darwin in the mid 19th century, the theory of evolution has withstood the scrutiny of generations of scientists. While it has been updated and revised to accommodate new observations and knowledge gained using modern technologies, as in the field of genetics, current evidence supports the theory of evolution more than ever. While the word “theory” is commonly used in casual conversation to mean something not proven, in the language of science, “theory” carries much more weight and means an idea is well supported by objective observations, experimental verification, and wide acceptance in the scientific community.

1.1.2 The Geologist’s Tools

the compass has a mirror and an arm
A Brunton brand compass, used commonly by geologists.
Observing natural phenomena is a key component of the scientific method. Geologists use tools in the field and laboratory to make observations about the Earth. In its simplest form, geologists may use a rock hammer for sampling a fresh surface of a rock, a magnifying hand lens to look at mineralogical details, a compass for location and documentation of orientation of geologic features, and maps to document and describe rocks and minerals in the field. A field geologist may use a magnet to identify magnetic minerals like magnetite or a dilute solution of hydrochloric acid to identify calcite, the main constituent of limestone.

The grain is round and has vesicles.
A sand grain made of basalt, seen with a geologist’s microscope. Box is 0.25 mm. Top picture is plane-polarized light, bottom is cross-polarized light.

In addition, geologists use microscopes and work in laboratories to perform experiments and acquire information. Rocks and minerals are more closely examined under lab microscopes. Soil may be analyzed for its composition and grain size in a lab. A laser and mass spectrometer may be used to vaporize a small piece of a mineral to precisely measure its chemical composition to determine the precise age of the mineral. Geophysicists use sensitive seismographs to record and map tiny vibrations made by distant earthquakes or ground penetrating radar to locate objects beneath the surface of the earth. They may also use complex computer simulations to integrate their data into models of the subsurface. Hydrogeologists drill wells to analyze water quality and its availability. Geochemists use a scanning electron microscope to view small minerals and measure their chemical compositions with x-rays. Other geologists analyze inclusions of liquids trapped in minerals or gases in glacial ice from the Antarctic.  Science advances as technology provides new tools for observation and newly seen evidence leads to new or revised ideas. The beauty of science is that it is ever advancing and learning.  Because the ultimate technology will never be discovered, the ultimate observation will never be made.

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1.2 Early Scientific Thought

The image is a likeness
Fresco by Raphael of Plato (left) and Aristotle (right).

Western science began in ancient Greece, specifically Athens, and early democracies like Athens encouraged individuals to think more independently than the in past when most civilizations were ruled by kings. Foremost among these early philosopher/scientists was Aristotle, born in 384 B.C.E., who contributed to foundations of knowledge and science. Aristotle was a student of Plato and a tutor to Alexander the Great, who would conquer the Persian Empire as far as India, spreading Greek culture in the process. Aristotle used deductive reasoning, applying what he thought he knew to establish a new idea (if A, then B). Deductive reasoning starts with generalized principles or established or assumed knowledge and extends them to new ideas or conclusions. If a deductive conclusion is derived from sound principles, then the conclusion has a high degree of certainty. This contrasts with inductive reasoning which begins from new observations and attempts to discern the underlying principles that explain the observations. Inductive reasoning relies on evidence to infer a conclusion, and does not have the perceived certainty of deductive reasoning. Both are important in science. Scientists take existing principles and laws and see if these explain observations. In addition, they make new observations and seek to determine the principles and laws that underlie them. Both emphasize the two most important aspects of science: observations and inferences.

The drawing is black and white of a man
1271 drawing of Avicenna (Ibn Sina). He is among the first to link mountains to earthquakes and erosion.

Greek culture was absorbed by the Romans. The Romans controlled people and resources in their Empire by building an infrastructure of roads, bridges, and aqueducts . Their road network helped spread Greek culture and knowledge throughout the Empire. The fall of the Roman Empire ushered in the Medieval period in Europe in which scientific progress in Europe was largely overlooked . During Europe’s Medieval period, science flourished in the Middle East between 800 and 1450 CE as the Islamic civilization developed. Empirical experimentation grew during this time and was a key component for the scientific revolution that started in 17th century Europe . Empiricism emphasizes the value of evidence gained from experimentation and observations of the senses. Because of the respect others held for Aristotle’s wisdom and knowledge, his logical approach was accepted for centuries and formed an important basis for understanding nature. The Aristotelian approach came under criticism by 17th century scholars of the Renaissance . As science progressed, certain aspects of science that could not be experimented and sensed awaited the development of new technologies, such as atoms, molecules, and the deep-time of geology. The Renaissance, following the Medieval period between the fourteenth and seventeenth centuries, was a great awakening of artistic and scientific thought and expression in Europe .

Earth is at the center.
Geocentric drawing by Bartolomeu Velho in 1568

The foundational example of the modern scientific approach is the understanding of the solar system. The Greek astronomer Claudius Ptolemy, in the second century, using an Aristotelian approach and mathematics, observed the Sun, Moon, and stars moving across the sky and deductively reasoned that Earth must be at the center of the universe with the celestial bodies circling around Earth. Ptolemy even had mathematical astronomical calculations that supported his argument. The view of the cosmos with Earth at its center is called the geocentric model.

The sun is in the center
Copernicus’ heliocentric model

In contrast, early Renaissance scholars used new instruments such as the telescope to enhance astronomical observations and developed new mathematics to explain those observations. These scholars proposed a radically new understanding of the cosmos, one in which Earth and the other planets orbited around the centrally located Sun. This is known as the heliocentric model and astronomer Nicolaus Copernicus (1473-1543) was the first to offer a solid mathematical explanation for it around 1543 .

This is a manuscript showing 4 moons of Jupiter.
Galileo’s first mention of moons of Jupiter.

Building on Copernicus’ heliocentric model of the solar system, two scientists, Johannes Kepler and Galileo Galilei, effectively jump-started the scientific revolution by radically challenging long established ways of thinking about nature and science . Johannes Kepler (1571-1630) was a German mathematician and astronomer who expanded on the heliocentric model, improved Copernicus’ calculations, and described the elliptical path of planetary motion. Galileo Galilei (1564 – 1642) was an Italian astronomer who used his newly developed telescope to observe the four largest moons of Jupiter . This was the first direct evidence that contradicted the geocentric model; moons orbiting Jupiter could not also be orbiting Earth. Galileo is said to be the first modern scientist because of how he conducted his experiments . Galileo strongly supported the heliocentric model and attacked the geocentric model , arguing for a more scientific approach . Because of this, he found himself at odds with the prevailing views and the Catholic Church, and was put under house arrest for the remainder of his life . The Scientific Revolution marked the beginning of a major shift in thinking about the world with more of an eye toward using evidence and experiments to understand the natural environment . Geology made great advances in this time, with scientists like James Hutton and Nicolas Steno. These are discussed further in chapter 7 and below. For the benefit of modern society, the scientific process has provided a solid foundation built on the conclusions of science.

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1.3 Foundations of Modern Geology

It shows a shark mouth and several teeth
Illustration by Steno showing a comparison between fossil and modern shark teeth.

As part of the scientific revolution in Europe, modern geologic principles developed in the 17th and 18th centuries. There are some key scientists who provided major contributions to geology during this periodNicolaus Steno (1638-1686) was a Danish priest who studied anatomy and geology. Steno was the first to propose that the Earth changed over time and that layers of sedimentary rocks, such as sandstone and shale, were originally formed horizontally with the oldest layers on the bottom and progressively younger layers on top .

The rocks are at different angles.
Siccar Point, Scotland, a famous angular unconformity examined by Hutton.
In the 18th Century, a Scottish naturalist named James Hutton (1726–1797) studied natural processes, such as rivers and coastlines, and compared the sediments they left behind to exposed sedimentary rock strata. From his observations, he hypothesized that the processes that formed the ancient rocks must have been similar to the processes producing those same features in the oceans and streams today. This idea is called the Principle of Uniformitarianism and states that natural processes that operate today also worked the same way in the past, i.e. that the laws of nature are uniform in space and time. Geologist often state it as “the present is the key to the past.” Therefore, geologists can understand ancient rocks by studying modern geologic processes today. Modern geologic processes operate slowly. Hutton realized that if these processes formed rocks, then the Earth must be very old, possibly hundreds of millions of years old. Hutton is also credited with being the first to propose that the Earth was much older than previously thought

It shows two views of each jaw.
Cuvier’s comparison of modern elephant and mammoth jaw bones.

Prior to the acceptance of Uniformitarianism, scientists such as the German geologist Abraham Gottlob Werner (1750-1817) and the French anatomist Baron Georges Cuvier, (1769-1832) thought rocks and landforms were formed by great catastrophic events. This view is known as Catastrophism. Cuvier championed Catastrophism and stated that, “The thread of operation is broken; nature has changed course, and none of the agents she employs today would have been sufficient to produce her former works.” Cuvier meant that processes that operate today did not operate in the past . Known as the father of vertebrate paleontology, Cuvier made significant contributions to the study of ancient life and taught at Paris’s Museum of Natural History. Based on his study of large vertebrate fossils, he was the first to suggest species could go extinct. However, he thought new species were introduced by special creation after catastrophic floods .

It shows a rudimentary cross section
Inside cover of Lyell’s Elements of Geology

Hutton’s Uniformitarianism and ideas about the age of the Earth were not well received by the scientific community of his time. His ideas were falling into obscurity when Charles Lyell, a British lawyer and geologist (1797-1875), wrote the influential Principles of Geology in the early 1830s  and later Elements of Geology. Lyell’s book promoted Hutton’s Principle of Uniformitarianism and supported the idea that Earth had to be very old, possibly over 300 million years old based on the study of rocks and the processes that formed them. Charles Lyell and his three volume Principles of Geology had a lasting influence on the geologic community. Eventually the Principle of Uniformitarianism and an old age for the Earth came to be accepted by the geologic community and the public at large . A contemporary of Lyell, Charles Darwin (1809-1882) had Lyell’s Principles of Geology book on his five-year trip on the HMS Beagle  where he used the ideas of Uniformitarianism and deep geologic time to help him develop his initial ideas about evolution , with Lyell being one of the first to publish a reference to Darwin’s idea of evolution. It took time, but eventually, the ideas of Hutton and his predecessors became established. The Principle of Uniformitarianism was so widely accepted in the geologic community, that catastrophic change was seen as heresy. Thi 400;”>by the weight of overlying sediments and cementation as minerals in groundwater glue the sediments together. The process of compacting and cementing sediments together is lithification and lithified sediments are considered a sedimentary rock, such as sandstone and shale. Other sedimentary rocks, known as chemical sedimentary rocks, are not made of weathered and eroded sedimentary fragments. They are instead made by direct chemical precipitation of minerals.

Swirling bands of light and dark minerals.
Migmatite, a rock which is partially molten. (Source: Peter Davis)

Pre-existing rocks may be metamorphosed into a metamorphic rock, meta- means “change”, -morphos means “form” or “shape.” When rocks are subjected to extreme increases in temperatures or pressures, the minerals alter into enlarged crystals or entirely new minerals with similar chemical make up. These high temperatures and pressures can occur when rocks are buried deep within the Earth’s crust or where they come into contact with hot magma or lava. In some cases, the temperature and pressure conditions can allow rocks to melt and create magma and lava, thus showing the cyclical nature of the rock cycle as new rocks are born.

1.4.2 Plate Tectonics and Layers of Earth

There are about 10 major plates
Map of the major plates and their motions along boundaries.

The fundamental unifying principle of geology and the rock cycle is the Theory of Plate Tectonics. Plate tectonics describes how the layers of the Earth move relative to each other. This especially focuses on the outer layer divided into tectonic or lithospheric plates. As the tectonic plates float on a mobile layer beneath called the asthenosphere, they collide, slide past each other, and split apart. At these plate boundaries, major landforms are created and rocks comprising the tectonic plates move through the rock cycle. Plate tectonics is discussed in more detail in Chapter 2.

Places with mountain building have a deeper moho.
The global map of the thickness of the crust.

The following is a brief summary of the Earth’s layers based on chemical composition (or the chemical makeup of the layers). Earth has three main geological layers based on chemical compositioncrust, mantle, and core. The outermost layer is the crust and is composed of mostly silicon, oxygen, aluminum, iron, and magnesium . There are two types – continental crust and oceanic crust. Continental crust is about 50 kilometers (30 miles) thick, represents most of the continents, and is composed of low-density igneous and sedimentary rocks. Oceanic crust is approximately 10 kilometers (6 miles) thick, makes up most of the ocean floor, and covers about 70% of the planet. Oceanic crust is high-density igneous basalt-type rocks. The moving tectonic plates are made of crust and some of the next layer called the mantle .  The crust and this portion of the upper mantle are rigid and called the lithosphere.  They comprise the tectonic plates.

The crust and lithosphere are on the outside of the Earth and are thin. Below the crust is the mantle and core. Below the lithosphere is the asthenosphere.
The layers of the Earth. Physical layers include lithosphere and asthenosphere; chemical layers are crust, mantle, and core.

The mantle is below the crust and is the largest layer by volume, extending down to about 2,900 km (1,800 miles) . The mantle is mostly solid and made of peridotite, a high-density rock composed of silica, iron, and magnesium . The upper part of this solid material is so hot that it is flexible and allows the tectonic plates floating on it to move about. Under the mantle is the 3,500 km (2,200 mi) thick core made of iron and nickel. The outer core is liquid and the inner core is solid . Rotations within the solid and liquid metallic core generate Earth’s magnetic field (Figure) .

1.4.3 Geologic Time and Deep Time

The circle starts at 4.6 billion years ago, then loops around to zero.
Geologic time on Earth, represented circularly, to show the individual time divisions and important events. Ga=billion years ago, Ma=million years ago.

In 1788, after many years of geological study, James Hutton, one of the early pioneers of geology, wrote the following about the age of the Earth: “The result, therefore, of our present enquiry is, that we find no vestige of a beginning, — no prospect of an end” . Although he wasn’t exactly correct (there was a beginning and there will be an end to planet Earth), he was trying to express the vastness of geological time that humans have a hard time perceiving. Although, Hutton didn’t assign an age to the Earth, he was the first to suggest that the planet was very old. Today we know Earth is approximately 4.54 ± 0.05 billion years old, an age first calculated by Caltech professor Clair Patterson in 1956 by radiometrically dating meteorites with uranium-lead dating . On a geologic scale, the lifespan of a human is very short, and we struggle to comprehend the depth of geologic time and slow geologic processes. Studying geologic time (also known as deep time) can help us overcome our limited view of Earth during our lifetime. For example, the science of earthquakes only goes back about 100 years; however, geologic evidence shows that large earthquakes have occurred in the past and will continue to occur in the future. Thus, human perspective of time does not always overlap with geologic time scales.

The Geologic Time Scale with an age of each unit shown by a scale
Geologic time scale showing time period names and ages. (Source: Belinda Madsen)

The following summarizes the geologic time scale, with more detailed discussions of geologic time and geologic history in Chapters 7 and 8. The largest division of time is the EonHadean, Archean, Proterozoic (sometimes combined together as the Precambrian), and Phanerozoic. Although life appeared more than 3,800 million of years ago (Ma), during most of Earth history from 3,500 Ma to 542 Ma (88% of geologic time), life forms consisted mainly of simple single-celled organisms such as bacteria. Only in more recent geologic time have more biologically complex organisms appeared in the geologic record. The Phanerozoic Eon, the last 542 million years, is only 12% of geological time and is named for the time during which visible (phaneros-) life (-zoic), i.e. abundant fossils, appeared in the geological record. Although simple life forms had been around for billions of years, the Phanerozoic marks the beginning of abundant multicellular animals having preservable hard parts such as shells. Animals have been on land for only 360 million years, or 8% of geological time. Mammals have dominated since the demise of the dinosaurs around 65 Ma, or 1.5% of geological time, and the genus Homo has existed since approximately 2.2 Ma, or 0.05% (1/2,000th) of geological time.

The fossil has bird and dinosaur features.
Iconic Archaeopteryx lithographica fossil from Germany.

Additionally, the Phanerozoic is divided into three Eras: Paleozoic, Mesozoic, and Cenozoic. Life of the Paleozoic (meaning “ancient  life”) consisted of invertebrate animals, fish, amphibians, and reptiles. The Mesozoic (meaning “middle life”) is known as the Age of Reptiles popularized by the dominance of dinosaurs, which evolved into birds, and Cenozoic (meaning “new life”) is the Age of Mammals in which mammals evolved to be the dominant form of animal life on land following the mass extinction of the dinosaurs and other apex predator reptiles at the end of the Mesozoic. Early humans (hominids) appear in the rock record only during the last few million years of the Cenozoic.

1.4.4 Evaluating Sources of Information

There is a large spike in earthquakes
This graph shows earthquake data. To call this data induced, due to fracking/drilling, would be an interpretation. Since the USGS (a reputable institution) has interpreted these earthquakes are caused by humans, it is a more reliable interpretation.

In the age of the internet, information is plentiful. It is important as a geologist, a scientist, or someone exploring scientific inquiry, to discern valid sources from sources of pseudoscience and misinformation. This is especially important in scientific research because many sources present a veil of science because science is so respected as a source for reliability . Courses such as this one can aid in this complex and crucial task. In its roots, all quality information has a basis in the empiricism of the scientific method , and has had such a role since the time of Aristotle. The objective nature of the scientific method aids in unbiased results. By definition, a valid inference should be based on evidence. Data and inferences (interpretations) should be clearly labeled, separated, and differentiated. This is done so that anyone looking over that data can understand where the author’s conclusion derived from, or, come to their own alternative conclusion. Procedures should be clearly defined so further replications or expansions of the investigation can occur. These make a scientific inquiry valid and its use as a source reputable. Of course, some work does slip through, and retractions are made by publications from time to time. One of the more infamous recent occurrences was a paper in the journal Lancet in 1998 linking the MMR vaccine to autism. After journalists discovered the author had multiple conflicts of interest and fabricated the data, the paper was retracted in 2010.

Logo for The Geological Society of America, one of the leading geoscience organizations. They also publish GSA Bulletin, a reputable geology journal.

When looking into any research, the author(s) should be investigated. While the author’s credibility is not based on one factor, having an education on the topics being discussed, as well as a funding source free from bias , can increase the reliability of an author. The same rigor should be paid to the publisher to ensure a non-biased process. One of the hallmarks of scientific research is peer review . If research is both substantial and innovative, than the scientific community should be able to observe the work. This allows reproduction of experimental results, corrections of errors, and proper justification of the research to experts. Citation is also important in reading scientific literature, as well as scientific writing. This is imperative to avoid plagiarism, but also to allow the reader to investigate the line of thought that brought the author to their investigations and conclusions. When reading scientific works, it is important to check that the citations are from reputable scientific research, as described above. Most often, scientific citation uses paraphrasing rather than quotes. The amount a work is cited is often used as a metric for the influence the investigation has had on the scientific community, though this technique has inherent bias .

1.4.5 Science Denial

There are several people around a sign
Anti-evolution league at the infamous Tennessee v. Scopes trial.

Introductory science courses usually deal with accepted scientific theory and credible ideas that oppose the standard accepted theories are not included. This makes it easier for students to understand the complex material. A student who further studies a discipline will encounter controversies later. But at the introductory level, the established science is presented. This section on science denial discusses how some groups of people argue that some established scientific theories are wrong, not based on their scientific merit but rather on the ideology of the group.

There are many people on the steps of the capitol.
2017 March for Science in Salt Lake City. This and other similar marches were in response to funding cuts and anti-science rhetoric.

When an organization or person denies or doubts the scientific consensus on an issue in a non-scientific way, it is referred to as science denial. The rationale is rarely based on objective scientific evidence but rather is based on subjective social, political, or economic reasons. Science denial is a rhetorical argument that has been applied selectively to issues that some organizations or people oppose. Three (past and current) issues that demonstrate this are: 1) the teaching of evolution in public schools, 2) early links between tobacco smoke and cancer, and 3) anthropogenic (human-caused) climate change. Of these, denial of climate change has a strong connection with geology. A climate denier specifically denies or doubts the scientific conclusions of the community of scientists who specifically study climate.

Shows three pillars labeled "Undermine the Science", "Claim the Result is Evil", and "Demand Equal Time".
Three false rhetorical arguments of science denial (Source: National Center for Science Education)

Science denial generally uses three rhetorical but false arguments. The first argument tries to undermine the science by claiming that the methods are flawed or that the science is unsettled. The idea that the science is unsettled creates doubt for a regular citizen. A sense of doubt delays action. Scientists typically avoid claiming universal truths and use language that conveys a sense of uncertainly because scientific ideas change as more evidence is uncovered. This avoidance of universal truths should not be confused with uncertainty of scientific conclusions.

The second argument attacks the researchers who’s findings they disagree with. They claim that the scientific conclusions are motivated by ideology and an economic agenda. They claim that the researchers want to “get more funding for their research” or  “expand government regulation”. This is an ad hominem argument in which a person’s character is attacked instead of the merit of their argument.

The third argument is to demand equal media coverage for a “balanced” view in an attempt to validate the false controversy. This includes equal time in educational curriculum. For example, the last rhetorical argument would demand that explanations for evolution or climate change be discussed along with alternative  religious or anthropogenic ones, even when there is little scientific evidence supporting the alternatives .  Conclusions based on the scientific method should not be confused with alternative conclusions based on ideologies. Two totally different methods for drawing conclusions about nature are involved and do not belong together in the same course.

The formation of new conclusions based on the scientific method is the only way to change scientific conclusions. We wouldn’t teach Flat Earth geology along with plate tectonics because Flat Earthers don’t follow the scientific method. The fact that scientists avoid universal truths and change their ideas as more evidence is uncovered shouldn’t be seen as meaning that the science is unsettled. Because of widespread scientific illiteracy, these arguments are used by those who wish to suppress science and misinform the general public.

The lines are similar when comparing smoking and cancer
The lag time between cancer after smoking, plus the ethics of running human trials, delayed the government in taking action against tobacco.

In a classic case of science denial, the rhetorical arguments were used in the 1950’s, 60’s, and 70’s by the tobacco industry and their scientists to deny the links between tobacco and cancer. Once it became clear that the tobacco industry couldn’t show that tobacco did not cause cancer, their next strategy was to create a sense of “doubt” on the science. They suggested that the science was not yet fully understood and issue needed more study, thus legislative action should be delayed. This false sense of “doubt” is the key component that misleads the public and prevents action .  This is currently being employed by those who deny human involvement in climate change.

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Science is a process. It has no beginning and no end, but aims to garner truth from studying the universe. Science is never finished, because a full truth can never be known. However, science (and the scientific method) is the best way to approach truth. Conclusions based on objective evidence will converge to single truths.  Geology is the scientific study of the Earth, beginning with scientists like James Hutton who declared the Earth has “…no vestige of a beginning, no prospect of an end.” Geology studies plate tectonics, the method by which the Earth causes mountains, earthquakes, and volcanoes; deep time, which explores the 4.5 billion-year history of Earth; the resources of the Earth; and many of the hazards of the Earth. Geology is just one of many ways that people educated in science can develop rational conclusions and overcome falsehoods in our society.

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