1.2 How Do We Study the Earth?

Carolina Londono Michel

Scientific method in Geosciences: Multiple hypotheses, multiple modes of inquiry

How is the process of science in the Earth Sciences? And why should you care? Even if you are not interested in becoming an Earth scientist, or any kind of scientist, understanding how science works is empowering. This is because science and scientific thinking are at the heart of our modern way of life and they influence every aspect of our lives. Understanding how science works can help you discern fact from fiction and inform your life choices and political decisions.

Backyard Geology
Image of an open crack in the middle, a Creosote tree on the side.
Figure 1.2.1 Earth fissures are deep and pose a hazard to humans and livestock. Geologists from the Arizona Geological Survey have linked these cracks with excessive groundwater withdrawal. Unfortunately, these cracks cannot be filled or covered, they severely impact landowners and make the land very restricted in its uses.


Modern science is based on the scientific method, a procedure that follows these steps:

  • Formulate a question or observe a problem.
  • Apply objective experimentation and observation.
  • Analyze collected data and interpret results.
  • Devise an evidence-based theory.
  • Submit findings to peer review and/or publication.


Earth scientists use a large variety of scientific principles and methods to understand how our planet works.


1. Observation, problem, or research question

The procedure begins when scientists identify a problem or research question, such as a geological phenomenon that is not well explained in the scientific community’s collective knowledge. This step usually involves reviewing the scientific literature to establish what is known and consulting previous studies related to the question.

Earth scientists can study processes they cannot observe directly. This could be because the events happen over long periods of time, happened long ago, or happened in a remote or inaccessible location. An example of the last one would be the Earth’s core. To circumvent these challenges, Earth scientists have developed strategies to test their hypotheses. These strategies make up the scientific method of geosciences.

2. Hypothesis

Once the scientists define the problem or question, they propose an answer, a hypothesis.This hypothesis must be specific, falsifiable, and based on other scientific work. Earth scientists often develop multiple hypotheses, not just one, and gather data and evidence from these multiple lines. To test hypotheses, scientists use methods drawn from other sciences, such as chemistry, physics, biology, or even engineering.

3. Testing Hypotheses: Experiments and Revisions

Experimental setup shows a funnel with a viscous, black substance falling into a beaker, all covered by a glass.
Figure 1.2.2 Experimental setup at the University of Queensland. A petroleum product has been dripping since 1927 at a rate of 1 drop per decade. The goal is to study the viscosity of what appears to be a solid.


The next step is developing an experiment that either supports or refutes the hypothesis. Earth scientists conduct classic experiments in the lab. However, an experiment can take other forms, such as:

  • Observing natural processes and their products in the field and comparing them to those found in the rock record. For example, a sedimentologist studies how wind moves and forms dunes and different ripples in a desert. This knowledge helps her to interpret ripple structures preserved in rocks, and even to interpret dunes and aeolian processes from images collected on Mars!
  • Studying changes across time or space. For example, an atmospheric scientist analyzes air bubbles found on ice to compare how the composition of the atmosphere has changed since the last glacial age.
  • Using physical models. This is more akin to the “classic experiment. For example, a team of scientists builds a model for landslides using a long and steep ramp at a certain angle. The scientists then model slides changing the sediment to water ratio, changing the sediment type and the ramp angle.
  • Using computer models. For example, climatologists develop computational models to study the climate system and make predictions. These scientific models undergo rigorous scrutiny and testing by collaborating and competing groups of scientists around the world.
  • Considering multiple lines of evidence. To establish a scientific finding, all lines of evidence must converge. That means that all the results you collect using different methods must agree with the finding, the math must be sound, and the methods must be thoroughly described.

Regardless of what form an experiment takes, it always includes the systematic gathering of objective data. The scientists interpret this data to determine whether it contradicts or supports the hypothesis (step 2). If the results contradict the hypothesis, then scientists can revise it and test it again. When a hypothesis holds up under experimentation, it is ready to be shared with other experts in the field. The scientific community scrutinizes the findings through the process of peer review.

Examples. Multiple lines of evidence and collaboration.
Layers of dirt, showing a gray layer in the middle and right below a dark horizon.
Figure 1.2.3 A sequence of sediments deposited by a tsunami. Scientists look for different lines of evidence to determine what and how deposited these sediments.


To determine past tsunami events, scientists compare the deposits left by modern tsunamis to those found in the rock/sediment record, such as the one pictured above. But how can you be sure that a tsunami indeed deposited the sediment sequence and not a landslide, a delta, or a sudden flood? To resolve this uncertainty, scientists examine other lines of evidence, for example, are there any fossils in the sediments? And if so, what type of organisms?; a landslide and a tsunami would not have fossils;  what is the age of the sediments? a tsunami would show sequences that are of the same age instead of spanning over longer periods of time; at which rate did the sediments pile up? a tsunami event piles up sediments almost instantly! and, was this event recorded somewhere else? Tsunamis have been seen across the Pacific Ocean so the deposits of one tsunami could be found in distant coastal areas, across the Pacific Ocean, for example!

The North American west coast has experienced tsunamis and earthquakes every 400 years on average due to the subduction zone between the Pacific plate and the North American plate (see Chapter 2). Indigenous Nations living on the west coast have stories of being nearly wiped out by tsunamis. Geoscientists Brian Atwater and collaborators have documented +9 magnitude earthquakes off the coast of Washington, but their results were met with skepticism by scientific community. They simply doubt the existence of such strong earthquakes!. Such an earthquake would have triggered a tsunami that would have been felt across the Pacific Ocean! At a geological society meeting with geologists from all over the world, the U.S. team found out from Japanese colleagues that Japan, which has a culture of incredibly detailed historical record-keeping, was similarly hit by tsunamis in the same time frame. The dates of the tsunami events, which were obtained with Carbon 14, showed a perfect match between the deposits of the Pacific northwest and Japan. Centuries of recorded observations on both sides of the Pacific by different cultures, and modern-day scientific collaboration, confirmed this discovery and resolved the question of the ‘Japan orphan tsunamis.’

Tsunami by hokusai 19th century
Figure 1.2.4 The Great Wave of Kanagawa, painted by Hokusai in the 19th century in Japan may depict a tsunami.



4. Peer review, publication, and replication

Science is a social process. Scientists share the results of their research at conferences and by publishing articles in scientific journals, such as Science and Nature. Reputable journals and academic outlets will not publish an experimental study until they have determined its methods are scientifically rigorous, and the evidence supports the conclusions. Before they publish the article, scientific experts in the field (not involved in the study) scrutinize the methods, results, and discussion; this is the peer-review process. Once a research group publishes an article, other scientists may attempt to replicate the results and use the findings to further their own research agendas. Replication is necessary to confirm the reliability of the study’s reported results. A hypothesis that seemed compelling in one study might be proven false in studies conducted by other scientists. New technology can be applied to published studies, which can aid in confirming or rejecting once-accepted ideas and/or hypotheses.

5. Theory development

A portray of a man smoking a pipe
Figure 1.2.5 Alfred Wegener revolutionized science with the idea that continents have been drifting. This was the precursor of the theory of plate tectonics. Portray by Achton Friis. Public Domain in the United States.


In casual conversation, the word theory implies guesswork or speculation. In the language of science, an explanation or conclusion made into a theory carries much more weight because experiments support it and the scientific community widely accepts it. A hypothesis that has been repeatedly confirmed through documented and independent studies eventually becomes accepted as a scientific theory.

While a hypothesis provides a tentative explanation before an experiment, a theory is the best explanation after being confirmed by multiple independent experiments. Confirmation of a theory may take years, or even longer. For example, the scientific community initially dismissed the continental drift hypothesis first proposed by Alfred Wegener in 1912 (see Chapter 2). After decades of additional evidence collection by other scientists using more advanced technology, Wegener’s hypothesis was accepted and revised as the theory of plate tectonics.

The theory of evolution by natural selection is another example. Originating from the work of Charles Darwin in the mid-19th century, the theory of evolution has withstood generations of scientific testing for falsifiability. It has been updated and revised to accommodate knowledge gained by using modern technologies, but the latest evidence continues to support the theory of evolution.


What is Science?

We covered the scientific method of geosciences. But science is a human endeavor, not the property or invention of any one culture. For generations, indigenous peoples have accrued empirical knowledge of the natural world, including the knowledge about the Earth system. Gregory Cajete, a renowned Tewa scholar, uses the name Native Science to refer to “the collective heritage of human experience with the natural world” (Cajete, 2000). Geologic expertise served Indigenous peoples in many of the same ways that Western geology serves modern civilizations. For example, Native Americans in Cascadia (NW US) coded volcanic eruptions and episodes in oral stories. Through storytelling, cross-generational awareness of volcanic hazards has been transmitted. Other examples of indigenous science are the Muisca (Colombia) knowledge for how to find, mine, and process the gold to make beautiful art pieces, and the Hohokam (North American Southwest) management of limited water resources using advanced water irrigation systems.  Western and Native scientists can collaborate to further our understanding of the Earth’s systems at the local or global scale.



Science is a dynamic process. Technological advances, breakthroughs in interpretation, and new observations continuously refine our understanding of Earth. We will never stop learning about our Earth. As new findings are published, we must revise and update our scientific knowledge and discard ideas that are proven false by new observations. Science is a living entity.

In conclusion, Earth scientists do not use a single, all-encompassing “scientific method.” Instead, multiple modes of inquiry respond to the complexity and spatial and temporal scales of Earth systems.

“The unique thing about the geosciences is that the knowledge, skills, and methods are brought together, refined, and developed over time to make them most suitable for understanding the complex processes of Earth, its working in the past and the present, and its likely behavior in the future” (Manduca & Kastens, 2012.)

Key Takeaways
  • Besides the classical laboratory experiment, Earth scientists construct models or use indirect methods to study the Earth.
  • Scientific results are not valid or useful unless other scientists can reproduce them. Research results undergo scrutiny by the community before and after being published.
  • The study of geological and environmental issues requires multiple disciplines and the interplay of multiple methods.
  • Scientific thinking advances through collaboration and community.


Hopetoun falls.jpg
Figure 1.2.6 The beauty of natural landscapes unspoiled by humans can serve as a reminder to act ethically.

Geoscientists must act in ethical ways to contribute to the welfare of human beings. The saying “with great knowledge comes great responsibility” holds true for Earth and environmental scientists. Earth scientists must uphold high standards in research and conduct. “Geoethics” is the area of study and reflection upon the values which underpin behaviors and practices between humans and Earth systems (Di Capua & Peppoloni, 2019). The International Association for Promoting Geoethics (IAPG) provides tools to “understand the complex relationship between human action on ecosystems and the decisions geoscientists make in the discipline that impact society, including improving the awareness of professionals, students, decision-makers, media operators, and the public on an accountable and ecologically sustainable development.” (Di Capua et al., https://www.geoethics.org/geoethics-school)

All of us, human beings, have responsibilities to Earth. We do not exist apart from this planet, we are part of the biosphere and our behaviors impact others in the biosphere, as well as the hydrosphere, atmosphere, and lithosphere. Our actions impact the entire Earth’s system. As you progress in your learning, strive to think critically and identify ethical issues. Do not be afraid to question and discuss your observations with your instructor and with peers. Just remember to do so respectfully, considering other points of view, and keeping an open mind.





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