What do you think of when you look at a rock? Have you ever picked up a rock that caught your eye and decided to keep it for yourself? What is tugging at you to do that? When I pick up an interesting rock or gaze at a road cut that beautifully exposes the layers of rock, often twisted and folded — what I like to call “tortured rock” — my first thought is usually “What’s your story?”.
This post is a bit different from my past posts. I’m reflecting on just a few of the things I’ve learned by observing, studying, and appreciating geology and rocks. My hope is that it sparks in you the same kind of reflection of what you have learned from observing the world around you. If you love to observe and identify birds, what have you learned from that process other than the names and identifying features of the birds? What connections can you make? If you have additional thoughts on what you have learned from looking at rocks, landscapes, and studying geology please share them in the comments below.
HOW TO BE A DETECTIVE
Much of the study of Geology involves tapping into creative and higher thinking processes to solve the riddle of the rocks. Just like how our own life’s memories become spotty and sometimes warped, with certain events recalled in sharp detail and others either skewed from reality or missing altogether, the rock record displays chapters of the Earth’s life that are sometimes clearly understood (a quick, easy read), sometimes altered (a convoluted mystery), and then there are chapters that are either hidden from view or lost altogether (banned or burned books). The further back in time you look, the less information is available due to billions of years of erosion; you have to be a good detective to uncover the clues and piece together the story of Earth’s history.
With the current rapid retreat of glaciers and melting ice caps, more chapters of Earth’s history are being revealed to us. The new information now available for study may lead to new insights into the Earth’s past. It’s like finding an old photo book from your childhood that had been lost, now calling up old memories — “Oh! I remember that vacation now, but who is that guy standing next to dad?”.
BROADENING YOUR PERSPECTIVE
The geologic timescale and thinking big…really big
As a visual learner, I like seeing spatial representations of the earth’s geologic history. One of the best I’ve seen is located at Fossil Butte National Monument in southwest Wyoming (a place well worth the visit!). The display starts at the beginning of the long road that leads up to the visitor center with a sign indicating the formation of the Earth, approximately 4.54 billion years ago. The timeline is set to scale, with every 9 inches equaling 1 million years of time. As you drive the road toward the visitor center, major geologic and biologic events are displayed — oldest known rocks at 4.055 billion years, photosynthesizing bacteria at 3.7 billion years, oxygen in oceans at 2.5 billion years, sponges and Earth covered in ice at 635 million years, jellyfishes and protective ozone at 600 million years — with a lot of unmarked space between the signs. At the parking area it continues, the signs getting ever closer — trilobites at 520 million years, Gondwana continent and C02 at twenty times today’s level at 500 million years, mass extinction (57% of genera) during the Silurian period, arthropods on land and oxygen at today’s level at 420 million years, mass extinction (83% of genera) and the Siberian Traps (flood basalts) during the Triassic period — the signs placed every few feet as you walk toward the building. At the visitor center, the timeline continues around an outside deck with signs even closer together — grasses and Rocky Mountains at 70 million years, hominid ancestors and the San Andreas fault come in together, the Pleistocene epoch ends with the first eruption of the Yellowstone caldera, and ending in the Holocene Epoch with the appearance of Homo sapiens and the beginning of recorded history. — the signs now very close together and sometimes piled on top of one another, like an overcrowded bookshelf.
It’s difficult for us humans to keep this long-term perspective of geologic time in mind as we make the decisions of today. Our individual minds, of course, only hold the memories of our own lifetimes along with some of the anecdotal stories of our known ancestors. However, we are often better served if we can take a giant step back from current affairs and telescope our minds back into the geologic past in order to get a clearer sense of where we are headed in the future.
Climate change and mass extinctions
As the saying goes, “the only thing you can count on is change” (quote attributed to Patti Smith). The rate of change to Earth’s geomorphology and communities of life happens within a very broad time span; either extremely slowly over very long periods of time (the cooling of a magma chamber, the building of a mountain range), quite suddenly (volcanic eruptions, earthquakes, landslides), or somewhere in between (slow earthquakes, evolution). Most of the changes to life on Earth are a result of climactic changes that stem from both geologic and astronomical processes.
The geologic record holds clues to ancient climactic tipping points that can help inform the course of our climactic warming and mass extinction event currently underway. We see evidence of the most recent glacial periods in our current landscape in the rocks and sediment glaciers left behind, and how these masses of ice cut into the underlying rock leaving behind U-shaped valleys. Evidence of older ice ages is found both in ice and sediment cores as well as in the fossil record, showing where various species of animals migrated in order to escape the ice and cold.
There have been 6-7 major mass extinctions on Earth (with the next underway now) and another 20 minor extinction events. The major extinctions, which terminated between 35-57% of all genera and 75-95% of all species, have all been caused by catastrophic events that suddenly changed the composition of Earth’s atmosphere which lead to rapid atmospheric warming (with one exception that involved rapid cooling). The geologic evidence points to events that disrupted the carbon cycle and carbon content in the atmosphere, such as extremely large meteor impacts and major volcanic eruptions that impacted the entire globe. Another notable commonality in these events is rapid changes in ocean chemistry leading to acidification and devastation to calcite-secreting organisms. The current mass extinction event is being caused by human activities that are (relatively) suddenly changing the climate by imparting too much CO2 into the air as well as causing habitat fragmentation by destruction of nature and severing the critical connections in food webs. All past extinctions were followed by a period of time — hundreds of thousands to millions of years — when microbes alone thrived while the rest of the biosphere struggled to make a comeback. None of the mass extinctions can be fully attributed to a single cause; all involved rapid changes in several geologic systems at one time and involved many of the culprits we are currently familiar with — greenhouse gases, carbon-cycle disturbances, ocean acidification.
Minor mass extinctions are also caused by global warming or cooling events. It has been shown that Ice Ages have occurred every 41,000 years for the past one to three million years. A century ago, a Serbian scientist, Milutin Milankovitch, hypothesized, and later proved through mathematics, that the long-term, collective effects of changes in Earth’s position relative to the Sun are a strong driver of long-term climate and are responsible for triggering the beginning and end of glaciation periods (Ice Ages). He showed how three types of Earth’s orbital movements affect how much and where solar radiation reaches the Earth’s atmosphere. The three orbital cycles are:
- Eccentricity: the shape of the Earth’s orbit changes from nearly circular to slightly elliptical on a 100,000 year cycle.
- Obliquity: the angle of the Earth’s axial rotation and the cause of Earth’s seasons. Over the last million years, the Earth’s obliquity has varied between 22.1 and 24.5 degrees with respect to the Earth’s orbital plane which affects how extreme the seasons are. Larger tilt angles favor periods of deglaciation. We are currently at an angle of about 23.4 degrees. The obliquity cycle spans about 41,000 years.
- Axial Precession: The Earth does not spin perfectly centered on its axis but wobbles, like a slightly off-center spinning top. This is due to tidal effects caused by gravitational forces from the Sun and the Moon that cause the Earth to bulge at the equator. The cycle of axial precession spans about 25,771.5 years.
The small changes resulting from these three cycles operate together and separately, and in conjunction with other Earth processes, to influence Earth’s climate over very long timespans. Milankovitch created a mathematical model to calculate differences in solar radiation at various Earth latitudes along with corresponding surface temperatures. He calculated that Ice Ages occur at approximately every 41,000 years — subsequent research on deep sea sediment cores and ice cores from Greenland and Antarctica have confirmed this cycle from between one to three million years ago. However, starting about 800,000 years ago, the cycle of ice ages lengthened to 100,000 years matching Earth’s eccentricity cycle. Various theories have been proposed for this transition yet there is no clear explanation. Research continues to better understand the mechanisms that drive Earth’s rotation and specifically how Milankovitch cycles combine to affect climate, but Milankovitch’s theory is well-accepted in the scientific community.
Our atmosphere has undergone at least four major changes in composition since Earth’s beginning. The story of the atmosphere is connected with the story of life on Earth; life itself is responsible for our modern atmosphere, generally keeping a stable balance of elements, but occasionally the rock record shows us there were times of atmospheric revolution and ecological catastrophe. We have a direct record of ancient air for the past 700,000 years from gas bubbles trapped in ancient snow which has been preserved as polar ice. For longer timescales, the rocks reveal to us the story of ancient air by providing several clues; the abundance of water, the evolution of life forms, and the emergence of free oxygen (O2) in the atmosphere — evident both in the fossil record and the appearance of iron formations. The appearance of O2 in the atmosphere began with the appearance of cyanobacteria and had such an impact on Earth’s geochemistry that it is named “The Great Oxidation Event” or GOE. The availability of O2 changed the chemical interactions between rainwater and rocks on land, altering the composition of lakes, rivers, and groundwater. The sedimentary rock record shows a change in rock types with more oxide minerals being present. The ozone layer established and shielded Earth’s surface from the ravages of ultraviolet radiation from the Sun, and the elemental exchange opportunities led to a strategic symbiotic merger —a tiny biologic structure that had learned to process oxygen, a mitochondrion, joined with a larger cell that would eventually lead to plants and animals.
Balance and tipping points
If you’ve read Malcolm Gladwell’s book The Tipping Point then you probably already have a good understanding of this concept. In fact, I think it is because of his book that this term has become fairly commonplace and well-understood. Geology offers some great examples of tipping points, again occurring over a broad time span. We can directly observe or experience sudden tipping point events such as avalanches, landslides, and earthquakes. These occur as a basic function of physics. In avalanches and landslides, for example, gravity wins when the forces acting on a slope exceed the strength of the material holding the slope in place. The Earth’s tectonic plates are always slowly (think geologic time slow) moving in different directions which, over time, builds friction in the rocks. An earthquake happens when the stress on the rocks reaches a tipping point and suddenly releases along a fault line allowing the rocks to slide past one another. Balance is the steady state where time passes in relative equilibrium. Chaos ensues when things are out of balance and change happens suddenly. Earth and nature are always working to restore balance; our collective humanity would do well to learn how to assist with this rather than continue to create tipping points.
Rocks and landscapes that we can either hold in our hand or observe from a distance may be extremely old but they are not static; instead of simply “being” they are always in the process of “becoming”. The formation, movement, and transformation of the three main rock types (igneous, sedimentary, and metamorphic) are a product of Earth’s internal heat and pressure from tectonic processes, along with the effects of water, wind, gravity, and biological actions. Each rock type is altered when it is forced out of its equilibrium state. It’s a beautiful, 100% no waste system of rock recycling— all elements either re-melted and made into new crystals or re-organized and morphed into new shapes and textures, and all rocks participate in the process. Contrast this with our production of plastic products, now observable collecting in mass quantities, from microscopic to large, absolutely everywhere on Earth — land, oceans, rivers — wreaking havoc on all life forms.
ART IS EVERYWHERE
If you look up the word “art” in a dictionary, you’ll be presented with all sorts of definitions that center around the production of some piece of work (painting, sculpture, drawing, etc) that was created by a human using a skill, an activity, or a method. I would argue that the creation of art is not singularly a human activity; art can be found everywhere in nature, including the rocks. My own definition of art may be: “A creation to behold which inspires awe, wonder, or simply a desire to linger and enjoy the positive emotions felt by the beholder.” The creator may be anyone or anything, including Mother Nature. Here are some examples of what I would consider art created by Mother Nature using rocks as her medium. Certainly a person took these photographs and lent their own vision of composing the scene to represent the beauty yet the same, if not more intense, feelings can be felt when viewing these areas in person.
Scroll through Dr. Marli B. Miller’s photo gallery to see examples of rock artistry at: https://geologypics.com/geological-item/instagram-pics/?undefined. Marli is a geology researcher and senior instructor at the University of Oregon. She is the author of Roadside Geology of Oregon, Second Ed.
Scroll through the photos above for some other examples of:
- Colors — Earth’s palette (Blue Basin, Oregon)
- Shapes — Rock molded by Earth’s hands: (Columnar basalts, Iceland)
- Patterns — the diverse layering and arrangements of rocks (Paria Canyon – Vermillion Cliffs Wilderness Area, Arizona)
- Fossils — the awe of ancient life, preserved in rock (Ammonites)
- Crystals — the beauty and variety of elemental arrangements (Amazonite and smokey quartz)
- Creation of new rock — the wonder of Earth’s tectonic processes (Cinder cone, Canada)
- Balancing acts — Rock defying gravity (Globe Rock, California). Why do humans like to create stacks of balancing rocks?
Going micro: zooming in on the details
A close friend and I like to take geology-focused road trips to enjoy and learn about the geology of our chosen area. After several trips together, I began to notice that there was a pattern to how each of us first “looked” at the rocks in an outcrop. I would stand back to take in the overall picture in front of us, then start zooming in to observe larger structures and smaller details within the outcrop — see the cross-bedding here, that looks like a fault over there. Starting to read the story held within the rocks. My friend likes to immediately focus in on the unique structure and beauty contained in individual rock hand samples. I like to say “she goes micro while I go macro”. Our different approaches are very complementary for each other. I make sure she sees and understands the larger geologic story while she takes me into the unique beauty held within an individual rock.
It’s the beauty held within a rock sample that leads my friend to “go micro” — their diverse colors, shapes, luster, and arrangements of minerals, and the reason why so many people are drawn to pick up and take a rock home with them. It’s one of the many ways we can learn to appreciate the beauty in nature. Whether looking at an outcrop of folded and mashed-up rock layers, an expansive landscape of glaciated granite peaks and valleys, or the stunning array of colors in a hand sample of jasper, the rocks are teaching us to recognize and appreciate the beauty found in nature.
SAFEGUARD YOUR VALUABLES
Water is Life
Rocks demonstrate the importance of sequestering precious resources. They serve as a great storage container for our life-giving water. The average water molecule stays in the atmosphere for about nine days; the residence time of water in the largest lakes is up to 200 years; deep groundwater may be stored in underground aquifers for 10,000 years. The amount of groundwater in an aquifer fluctuates over time depending on water input and outflow, The aquifer fills, or recharges, as surface water filters down through soil and rock and depletes as it is pumped back to the surface for human consumption or migrates to another region in a subsurface flow. Currently, climate change has shifted global weather patterns that have led to both drought and flooding, altering the amount of recharging to aquifers, while humans continue to draw from the aquifers at the rate we have become accustomed to.
The family jewels
The Earth has created many elements and minerals that humans have found irresistible, however we have yet to learn to respect and use these resources with care and conservation. There are places on Earth that some indigenous groups hold sacred, yet others come along in disrespect and destroy by mining, logging, or paving over. A majority of the man-made items you can reach out and put your hands on right now, including the computer I am writing on, are available to you thanks to the mining of Earth’s precious elements and minerals. The top 10 minerals extracted for human use are: copper, feldspar. lithium, silver, gold, iron ore, nickel, beryllium, and molybdenum. As of 2017, the U.S. government keeps a list of 35 elements and minerals that are “…essential to the economic and national security of the United States…the absence of which would have significant consequences for the economy and national security.” Our human lives as we know them are dependent on these 35 elements and minerals. They bring us batteries, pesticides, cement, steel, gasoline, integrated circuits, LED’s, fertilizers, fireworks, magnets, solar panels, nuclear fuel, glass, lubricants, microchips, medicines, paint, plastics, and oh-so-much more. Some of these minerals are found only in low concentrations making them difficult and expensive to mine. About 98% of the Earth’s crust is made up of only eight elements: oxygen, silicon, aluminum, iron, calcium, sodium, potassium, and magnesium. Everything else on the periodic table makes up the remaining 2%. It is estimated that every person in the U.S. will use more than three million pounds of rocks, minerals, and metals during their lifetime (!!!) — that’s a human lifetime, as compared to the time it took for the minerals to form (again… geologic timescale). Who do those materials belong to? Who is profiting from extracting them? Whose habitats are destroyed in the process of extraction?
Our lesson here from the rocks is that Earth’s precious resources, like clean water, clean air, precious elements, and minerals, are in limited supply and belong to all beings that live in community on the planet. They must be treated with the utmost care in a sustainable way for the benefit of all.
MAKING THE CONNECTION: Our place on earth
I’ve picked up from my desk one of the many rocks I’ve collected from somewhere during my travels here and there. It’s a piece of grey sandstone a bit larger than the size of a quarter — a good pocket rock. Several thin lines of white quartzite run through the sandstone and a thicker section of quartzite caps the “top” of the stone. It’s a well-polished stone — probably picked up off the Oregon coast — mostly round, but more tapered under the thicker layer of quartzite. It’s this taper with the thicker quartzite cap that makes me always want to hold it with this part oriented up. I guess it reminds me of a snow-capped mountain peak…maybe a clue to it’s origin. If I hold it just right in the light and look closely, tiny grains of quartz wink back at me. When I look at it through my microscope, the individual grains of quartz, feldspar, and biotite or hornblende come into focus. As I hold it in my hand and focus my attention on it, it starts to tell me it’s story; glacial erosion of an old Cambrian granite batholith, further weathering and transport by river action, deposition, burial, and millions of years of pressure and heat causing compaction and some dissolution of the mineral grains, cementation by fluids charged with dissolved minerals. The quartzite veins formed during this stage when the rock fractured and silica-rich fluid filled the fracture zones which, after more time, crystalized. This rock had a cozy, stable home for a long time while this process was happening, but at some point tectonic forces pushed and shoved the rock back to Earth’s surface where it eventually broke free and tumbled once again into a river where a series of flooding events picked it up and carried it off to the ocean. Here it was tumbled about by wave action, further smoothing the edges and wearing away the sandstone until one day I happened to come along to spy it and feel inclined to pick it up, admire it, and take it home with me.
From Timefulness by Marcia Bjornerud: “Young rocks communicate in plain prose, which makes them easy to read, but they typically have only one thing to talk about. The oldest rocks tend to be more allusive, even cryptic, speaking in metamorphic metaphor. With patience and close listening, however, they can be understood, and they generally have more profound truths to share about endurance and resilience.”
The most important lesson we may learn from our observations and study of geology is to be able to take the long view of Earth and life through time. The ability to do this allows us to be able to confront issues we currently face against the backdrop of the bigger picture of the stories of life through time; the recurring themes and chapters, the evolving cast of characters, sudden drama, and clear-eyed solutions. Many humans have forgotten the value of nature and the role we play in nurturing nature and working respectfully together with all forms of life that share the resources of this planet. When we become familiar with the narratives of natural history, we come to feel a connection with everything on the planet. The rock record reveals how our bodies are part of a continuum made from the raw materials of the earth — our bones made up of the calcium and phosphorus minerals derived from rock, our blood a distant memory of seawater — we are part of an unbroken chain of living organisms that stretches back to the very earliest days of our planet. As Earthlings, we are fully native to Earth.
- Bjornerud, M. (2021). Becoming Earthlings. Kinship: Belonging in a World of Relations, Vol. 01 Planet, pp 13 – 20.
- Bjornerud, Marcia, Timefulness: How Thinking Like A Geologist Can Help Save The World, New Jersey: Princeton University Press, 2018, print.
- Strauss, B., “The Earth’s 10 Biggest Mass Extinctions”, Feb 02, 2020, Retrieved from www.thoughtco.com
- Brovkin,V., et.al., “Past abrupt changes, tipping points and cascading impacts in the Earth system”, July 29, 2021, Retrieved from USGS Publications Warehouse
- “List of Extinction Events”, Retrieved from en.Wikipedia.org
- Buis, A., “Milankovitch (Orbital) Cycles and their role in Earth’s Climate”, Feb 27, 2020, Retrieved from www.climate.nasa.gov
- “Understanding Global Change”, Retrieved from www.ugc.berkeley.edu
- “Groundwater Storage and the Water Cycle”, June 18, 2018, Retrieved from www.usgs.gov
- Alden, A., “What is Sandstone?”, Aug. 13, 2019, Retrieved from www.thoughtco.com
- Motavalli, J., June 19, 2010, Retrieved from www.cbsnews.com
- King, H.M., “REE — Rare Earth Elements and their Uses”, Retrieved from www.geology.com
- Conca, J., Nov. 19, 2019, “35 Minerals That Are Critical To Our Society”, Retrieved from www.forbes.com
- Silva, J., July 21, 2016, “Top 10 Minerals Mined in the U.S.”, Retrieved from www.blog.midwestind.com
- “Rocks and Minerals: Everyday Uses”, Retrieved from www.mnch.uoregon.edu