This morning I went on a hike with some other women from my graduate program and we got to talking about various things, one of them being how cool Tucson is compared to Phoenix (at least that’s my opinion). I have come to love a lot of things about Phoenix and there are definitely a lot of cool spots around the Valley of the Sun, but Tucson overall just seems so much more hip – more “artsy” – and is a lovely relatively nearby place to travel (especially in the summer months when it’s just a little bit cooler there). I can’t wait to go back and try this place a friend recommended called “Barista del Barrio” because I’m told they have the best breakfast burritos there (they “slap”, I’m told).

But that got me thinking about Tucson and about how almost two years ago, I travelled to there from Phoenix for Memorial Day Weekend. It was my first time actually visiting, instead of just passing through on the way to somewhere else. I’ve been back a couple of times since then, once for rock climbing at Mt. Lemmon and once to stay at the luxurious Ritz-Carlton resort just outside of the city.

During that first trip, though, we decided to head a couple of hours East past Tucson to a place called Chiricahua National Monument. We camped in the Coronado National Forest for the night (“Land of Many Uses”) and went hiking the following day. We did a hike called the Echo Canyon Loop which offered a short, easy hike with incredible views of the area.

Chiricahua is known by the National Park Service as the “Wonderland of Rocks”, a very appealing place name for a geologist like me. There are many geologic features to be admired in the entirety of the Monument; however, one of the most striking are the rock pinnacles made up of a rock type called rhyolite (or more specifically, rhyolitic tuff).

Rhyolite is an igneous rock which means it formed from the solidification of molten rock. In the case of rhyolite, this solidification occurred above the surface of the Earth, so it came from particles of lava (which is different from molten rock below the surface – called magma). Igneous rocks are classified based on two major things (1) their texture (which has to do with the process by which they form) and (2) their composition, or mineralogical makeup. Rhyolite has a “fine” crystalline texture due to rapid cooling at the surface and it has a silica-rich (or felsic) composition. Rhyolite is basically the extrusive (forming above the surface) equivalent of granite (which is intrusive or forming below the surface). This rock formed from the solidification of ash from a massive eruption of a large volcano known as the Turkey Creek Caldera about 27 million years ago.

Anyway, in my opinion, the most interesting thing about the rock at Chiricahua are the “pinnacles” that I mentioned previously. These pinnacles formed from erosion over time to form structures known as “hoodoos”. These structures occur elsewhere, like as the famous hoodoos of Bryce Canyon National Park in Utah. Generally, the base of the rock erodes more easily than the top so spires form.

The rhyolite pinnacles of Chiricahua National Monument in Southeast Arizona.

Some hoodoos are similar to another geologic feature known as the Precariously Balanced Rock (PBR) because often, the difference in erosion between a lower area on the hoodoo and the upper part is so intense that it appears to be precariously balanced. Though not a true “PBR”, these so-called pedestal rocks are strikingly similar in appearance.

Pinnacle Balanced Rock at Chiricahua National Monument (a pedestal rock) formed when erosion undercut the base.

I like to think about natural phenomena and how they relate to things that I encounter through the human experience. One such thing that these pedestal rocks at Chiricahua reminds me of is how I often struggle with finding balance in things. Whether that be my work-life balance or how intensely I pursue a new interest or activity, I often find that I engage in an all or nothing sort of mindset. So, through making small changes, planning, and just generally trying to do things in a more moderate way, I’m slowly getting better at finding balance.

Central Arizona is typified by landscapes consisting of flat sandy to rocky expanses interrupted by small mountain ranges and peppered with cacti like the iconic saguaro or the organ pipe variety. To the outsider, it may seem deathly dry and desolate, with a paucity of the life-sustaining substance known as water.

However, the Colorado River, which runs through the iconic Grand Canyon in Northern Arizona makes its way across the desert through its expansive watershed. Near Phoenix, the Colorado River expresses itself – first as the Gila River, and then as the Gila’s largest tributary – the Salt River.

This urban desert oasis offers numerous opportunities for recreation. In fact, it’s quite popular for folks to engage in tubing of the Salt River. Essentially, Phoenix area locals love to grab an inflatable tube and drift with the current along the Salt River to designated drop ins designed for this purpose. I’ve engaged in this activity a couple of times, making new friends and getting pretty badly sunburned.

But last time I went to the Salt River I was for the Field Geology class I’m taking this semester. We were there focusing on the Quaternary Geology of Salt River Terraces. Let’s unpack that for a second. First, the Quaternary is a geologic Period. Geologic time spans the age of the Earth (about 4.5 billion years) and within this long time span are Eons. The majority of geologic time occurs during the first three Eons (Hadean, Archaen, and Proterozoic) which are collectively known as the Precambrian. Further subdivisions (Eras) give the Paleozoic, Mesozoic, and Cenozoic, the last of which is most recent. Within the Cenozoic are Periods: the Paleocene, the Neogene and the Quaternary. The Quaternary is the most recent of the Cenozoic Periods and began about 2.6 million years ago. So Quaternary Geology focuses on the most recent 2.6 million years of geologic time (which may seem like a lot but in the grand scheme of things is relatively recent).

The terraces that I mention are landforms that can occur as a result of two different river processes, each resulting in a different type. There are strath terraces, on the one hand, which form when a river cuts laterally into bedrock (in other words, not just cover deposits). Over time, the river abandons its position over which it was cutting into the bedrock and leaves a bench that is composed of bedrock mantled by a thin layer of sediments. The other type of terrace is called a fill terrace and it is a feature that is composed entirely of sediment (a result of an existing river valley being filled with river deposits, or alluvium). Also abandoned, the resulting “bench” is composed of this alluvium.

During my trip, we were out mapping both types of terraces of the Salt River. The fact that the terraces exist tell us that the river evolved through time because we know that terraces result from a river abandoning its former path. Why then, does this happen? Well, let’s begin by discussing the two primary factors in determining a river’s evolution: sediment load and transport capacity. Sediment load is the total amount of sediment that the river transports. It includes what gets dissolved, what is suspended in the water, and what moves along the riverbed through rolling, sliding, and bouncing (known as “bed load”). Transport capacity is the amount and size of sediment that the river has the energy to transport. The energy level of the river is influenced by the water’s velocity and depth, which are controlled by channel slope and dimensions, discharge, and the roughness of the channel.

These two factors determine whether the river will erode through the bedrock, deposit sediment, or dynamically balance those two processes. For example, if the transport capacity exceeds the sediment load, the river has more potential to do work and the sediments being delivered are relatively low, therefore the river will erode. In the reverse scenario, more sediment is being delivered than the river has the ability to transport so the net effect is that sediments get deposited. If the transport capacity is equal to the sediment load, the river is in a state of equilibrium and there is no net erosion or deposition.

Changes in climate, as well as tectonic setting, will affect both the sediment load and the transport capacity but the relationships can be quite complicated. Generally, cooler temperatures are associated with wetter climate and therefore greater transport capacity. Additionally, glaciers are really good at eroding surfaces. In warmer climates, there is generally less precipitation and lower transport capacity so one might see more deposition. It’s not so straight forward, however, and it’s complicated further by the possibility of tectonics changing the overall slopes of the landscapes as well as uplifting land and changing the distance to a river’s local “base level” or the lowest level of an erosional process (an example is sea level).

Anyway, whether it be through climate, tectonics, or some combination of the two, rivers have a tendency to change their positions through time and this is preserved in the landscape in the form of strath and fill terraces and the goal of our field trip was to identify different known terraces (based on age, morphology, and location in the landscape) and map them.

This field trip was useful to me because it helped me to further develop my ability to sketch geologic processes in my field notebook as I thought about them in relation to the geology I was seeing. I’ve often lacked confidence in my artistic abilities, but I’ve been getting more comfortable over time with just accepting that what I produce may not be incredibly photorealistic or even that aesthetically pleasing. Yet, I’ve found that sometimes the best way to record geologic observations is to do a sketch and not worry so much about my expectations of what I think it should look like. That being said, I include one of my field sketches below.

Another important lesson I learned from this field trip was that it is sometimes convenient to work from a model when trying to extrapolate information gained in the field. Basically, if you begin to notice a pattern of where a certain rock tends to be and you don’t have time to cover the entire area of the map you’re trying to produce, you can use your geologic knowhow to make an educated guess as to what rock might be in a place that is difficult or time consuming to reach. I applied this lesson during the field trip, noticing that a lot of times, the terraces contacts with each other tended to follow topographic contours so I was able to fill in certain areas of my map without actually seeing the rock. Sometimes, this worked, and I was correct but other times the model that I had developed in my mind failed me. This reminded me that while models are ultimately useful in a lot of instances, they can potentially be wrong, which I think is an important lesson for a developing geologist.

This semester I’m taking an undergraduate field geology class called Field Geology I. It’s intended to be a geology student’s first course in geologic field studies.

Since I didn’t do my undergraduate degree in geology (I used to be an engineer), I never took such a course. Following my qualifying exam for my PhD, my committee made a recommendation that I take the course. I took my committee’s recommendation seriously and decided to enroll in the course and I’m happy that I did.

Geologic field studies are an important part of being a geologist. Some even say “the best geologist is the one who’s seen the most rocks”. The field is where the products of geologic processes can be observed at various scales: from an entire outcropping of rock to a sample of rock that can be held in your hand, and even to what can be seen through a magnifying hand lens. There are of course other scales at which geologic observations can be made (from the global scale to the microscopic), but the three mentioned above are most relevant for field studies.

There are a lot of geologic skills that are at play when working in the field. One thing that we’ve been doing in the course thus far though is field mapping. Mapping basically consists of identifying rock types and geologic structures, figuring out the relationships between the different rock units and structures, and finally constructing a geologic history based on your observations.

This may seem simple: how hard can it be for a geologist to identify a rock? One might ask. But I’ve found that nothing is quite as simple as it may first seem when it comes to field studies.

For example, on our first field trip of the semester we went out to a place called Goldfield in central Arizona. Perhaps you’ve heard of Goldfield from it being a “ghost town” or perhaps even visited the tourist attractions there. But Goldfield is also a locality rich in interesting geology.

The rocks there are mostly igneous rocks (formed from molten rock) but there are also some sedimentary rocks (formed from sediments) present. There are also so-called geologic structures (specifically, faults) that make the field relationships a little more interesting.

For the rest of this post I’ll write about one stop that we found particularly interesting. I’ll start with a picture of my mapping partner Logan, approaching the feature we identified from afar. He’s trying to get a better look. He also provides a scale, which is important when thinking about the relative sizes of features. Logan is about 2 m (6.5 feet) tall.

Notice anything? Maybe the picture isn’t that great. I did leave my camera on the bus and I was trying to use Logan’s camera for the first time. But what we noticed first was that there were two different rock types here: the reddish brown type (what we called the red unit) on the left side of the photo and the grey to brown rock (what we called the brown unit) on the right side of the photo. The surface of the red unit (seen just above Logan’s head) is also distinctive in that it is unusually flat and close to vertical and the rocks surrounding the “contact” between the two units seem to be broken up a little more than rocks farther away from the contact.

I annotate the photo to make some of these observations a little clearer, the red color is the red unit, the brown color is the brown unit, and the black lines show the fractured zones.

Now, I said the red unit is distinct from the brown unit but how is it distinct, exactly? Well they clearly look different, so what does that mean?

The red unit appears to be composed of pieces of other rocks (clasts), which means it’s sedimentary. In the following photo, I crop some of the red unit out and highlight this feature by outlining some of the cobble-sized clasts of which the red unit is comprised. The arrow is pointing to a cavity where it looks like one of these clasts weathered out. You can also see that these clasts are very rounded or smooth. You also see there are not just larger clasts but also smaller ones as well. Finally, there’s a finer grained matrix that holds everything together.

Have you guessed the name of this rock yet? It’s called a conglomerate. The sizes of the clasts that make up the rock a variable (poor sorting) and the clasts are fairly well rounded.

When we look closer at the types of clasts that make up the conglomerate we see that a lot of them are made of crystals that are visible to the naked eye, these crystals are light in color and lack any type of preferred orientation. These characteristics lead us to believe that most of the clasts are made of granite. When geologists try to surmise the potential sources of sediment it’s called provenance study. So these clasts came from an area that had a lot of granite around.

Another thing that can be inferred from this rock is the environment of deposition. If we think about the sizes of the clasts and the roundness, we can conclude that the environment provided enough energy to transport large pieces for long enough (and therefore far enough away) to round out the clasts. One example of a setting with these characteristics is a river.

So what about the brown unit? Well, I don’t have a better picture of that unit, unfortunately. But, the rock is made of medium to dark grey crystals. Some of these crystals can be seen with the naked eye, but most cannot. We can also identify some of the minerals that are more visible and find that the rock is composed of weathered olivine, pyroxenes, hornblende, and some feldspar minerals. We call this rock basalt, which is an extrusive igneous rock. That means it formed from molten rock that was above the surface of the Earth, like from a volcano.

Now we ask ourselves, how did these two rock types get placed next to each other in the orientation that they currently have? One of the basic principles of geology is that rocks get deposited or emplaced in a horizontal position; however, these rock units are nearly vertical! Also, we know from other field relationships that the red unit is younger than the brown unit and there isn’t a history shown in the rocks of the transition from a volcanic environment to a river (fluvial) environment. Therefore, questions remain about the temporal relationships of these units. Well, luckily there’s another feature that helps explain some of this.

If you remember, I mentioned that the rocks are fractured a lot more closer to the contact between the two units. We also see evidence of slight polishing of the red unit on the left hand side of the contact. This and other evidence in other places nearby allow us to conclude that these two units were placed next to each other by a fault. The fault is oriented nearly vertically in most places but has a slightly shallower dip in this location.

A principle known as cross-cutting relationships allows us to date the fault relative to the rock units. We know that the rocks had to exist prior to being faulted. Therefore, the faulting of the rocks happened after the deposition of the two units.

These rocks (and perhaps the fault as well) were tilted at some point also. I mentioned before that rocks get deposited horizontally (the principal of original horizontality). But these rocks were rotated to become nearly vertical. This may have happened at the same time as faulting of the units or the timing may be different. I can’t really say for sure at this point but with more field study and research about the area I could probably form a more complete hypothesis.

That’s one fun thing about geologic field studies, though. Sometimes the relationships and the associated geologic history aren’t clear after only a day or two of field observations. Luckily we have other tools to help address uncertainties, some being field-based and others being laboratory or modeling based.

The professor of my field course has us end our field trip with a summary of what we did, what we observed, how we interpret it, and finally, what questions remain. I like ending with the questions part because it reminds me that with science, there’s always more to explore.

Last semester, my students were assigned a project titled “Hometown Geology” in which they were to find (1) a topographic map and (2) a geologic map of an area of interest. They used the maps to learn about the geology of the selected area; specifically, how topography and geology are related as well as identify rock types, geologic features, and reconstruct a geologic history.

One of my students chose the area of Oak Creek Canyon in Sedona, AZ. This student did well on the assignment and little did they know, they were helping me familiarize myself with the geology of area I would soon visit for a hike.

This past Christmas Eve, a couple of friends and I embarked on a journey north of Phoenix to hike Sedona’s tallest peak, Wilson Mountain. One of the friends joining me had one hike left of a Northern Arizona six peak hiking challenge she was unofficially participating in so we chose this hike to do together. It was purely coincidence that one of my students also took an interest in Wilson Mountain, which rises high adjacent to Oak Creek Canyon in Sedona.

Also a coincidence is the fact that the street I grew up on, the first 18 years or so of my life, was called Oak Creek Place. I have fond memories from my youth there on Oak Creek Place and I’m taken back to those memories whenever I’m near Oak Creek Canyon. So I suppose you could say my student’s “Hometown Geology” assignment reminded me of my own hometown.

Oak Creek Canyon is a beautiful river gorge located between Flagstaff and Sedona in Northern Arizona. Oak Creek carved Oak Creek Canyon along the Oak Creek Fault. The Oak Creek Fault is a normal fault that makes it so that the west side of Oak Creek Canyon (the foot wall) is about 600 ft higher in elevation than the east side (the hanging wall). An east-west cross-section through Oak Creek Canyon is shown below. Here you can see how the rock layers have been tilted and offset.

The Oak Creek Fault originally formed about 65-75 million years ago, during a period of compression in western North America. Later (about 25 million years ago), the region began to extend and related to this was outpouring of a series of basalt flows through Oak Creek Canyon along Oak Creek Fault. The fault was later reactivated and offset of these basalt flows occurred.

The mountain we hiked up – Wilson Mountain – is on the west side of Oak Creek Canyon and is higher in elevation due to this faulting activity. The peak of Wilson Mountain rises to a little over 7,000 ft in elevation, which makes for a rewarding hike and great views of Wilson Canyon (south of Wilson Mountain) and its surroundings!

View of Wilson Canyon from Wilson Mountain Overlook. The red colored rocks are the Supai Group sedimentary rocks labeled in the above cross section and the white colored rocks are the Coconino Sandstone. In the foreground are boulders of the Neogene Basalts that cap Wilson Mountain.

Overall, I consider myself a generalist (despite that I’m going for a PhD right now). That means I like to know at least a little bit about a lot of different things. There are also specialists, or people who know a lot about one or a few related things. I’m also a bit of a specialist in that I’m seeking to know a lot about my dissertation research but my dissertation research combines many concepts that span multiple disciplines.

For example, I use computers to understand how plate motion affects the outermost layer of the earth. That means I need to know about computers, software, and coding in addition to the geological concepts that I use. Further, the geological concepts I need to know combine mathematics, physics, chemistry, and materials science. The physics of the processes that result in mountains are described mathematically using numerical models for heat and material transport. Also, the way stress affects rocks (which occurs due to plate motion) depends on chemistry or mineral composition and is a function of temperature. Then there’s the geology which incorporates a lot of subdisciplines like computational geodynamics, structural geology, isotope geochemistry, geomorphology, seismology, and mineral physics, to name a few.

So when people ask me what I do, I often have a different answer depending on the situation and the person asking. Basically, I have a lot of options for responses. But if I want to put it into one term: I say I’m a tectonicist.

It works because Plate Tectonics is the grand, unifying theory of geology. That is, it ties together all of the aspects of earth science, which makes it pretty darn important.

This week, my lab students have elected to learn about plate tectonics. They cast votes – unbiased by me – and chose my favorite topic. So I’m using this blog to teach them (and you!) some basics.

The simple idea behind plate tectonics is that the lithosphere – the outermost portion of the earth which includes the continental and oceanic crust and the uppermost mantle – is broken up into rigid sections called plates that “float” on a weak part of the mantle called the asthenosphere. Below the plates, the mantle convects – similar to how water convects in the pot when you’re boiling it on the stove – and this convection results in motion of the overlying tectonic plates.

Plates move relative to each other in three different ways at plate boundaries. They can push into each other – which is known as a convergent plate boundary, they can move away from each other – which is known as a divergent plate boundary, and they can move past one another – which is known as a transform plate boundary. The interactions at plate boundaries result in many geologic features and phenomena that are observed on earth. For example, mountains, volcanoes, and earthquakes are all related to motion at plate boundaries. Sometimes, some of these features occur inside of a plate instead of at a boundary but that’s due to a different phenomenon you can learn about here.

My lab students will learn about the different features associated with these types of plate boundaries as well as the hazards associated with each.

Hopefully, I’ve piqued your interest in plate tectonics and if you want to learn more, continue reading my blog because plate tectonics has it all and is always on my mind!

I like pretty things, which is why I’m drawn to geology as a discipline. There is beauty to be found in many aspects of the science – at all scales.

You may have guessed that I’m a fan of large scale formations that result from large-scale processes (mountains! tectonics!). But I’m also a fan of the micro-scale – things that can be observed using a microscope.

Geologists call the special optical microscopes that they use petrographic microscopes and the study of rocks that uses such a microscope is called petrography.

To study rocks under the petrographic microscope, it has to be cut thin enough for light to pass through. Geologists use something called a thin section – or thin slices (usually 30 microns or 30/1,000,000 meters thick) – of a rock or mineral sample. Thin sections are usually mounted on a slide with adhesive and measure 26 x 46 mm but the size and shape can vary depending on the application. Also, there are different ways to treat thin sections, like embedding them with different media, staining them to highlight different minerals, or coating, covering, or polishing them differently so that they are compatible with different types of light or microscopes. If you want to learn more about making thin sections see this excellent website.

Petrographers use polarized light microscopy to observe features in the thin sections. Polarization acts as a filter to isolate waves of light along particular planes. If you think of the way a guitar string vibrates up and down along the length of the string it’s similar to how light propagates through space. The difference is that there are different orientations of the waves and polarized light takes out some of the orientations. The graphic below illustrates how light travels in directional waves and how the polarizer works to filter it.

Polarizers are used by petrographers because the minerals that make up rocks exhibit an optical property called birefringence which means the mineral looks different depending on the nature of polarization. The way the mineral looks under different polarization (plane-polarized versus cross-polarized, for example) can be used diagnostically – that is, it is useful for identifying and characterizing the mineral and it’s history.

Plane polarization is when only a lower polarizer is used and cross polarization is when a lower polarizer and an upper polarizer (also called the analyzer) are used. Properties that can be observed using plane-polarized light microscopy include opacity (degree to which a material transmits light), color, pleochroism (when a material changes color as it rotates relative to the polarizer), refractive index (the speed of light in the material relative to that in a vacuum), and relief (the difference in refractive index between a material and its surroundings).

Under cross-polarized light, minerals reveal very interesting properties, many of which are slightly too technical to describe in detail here. One example; however, is called twinning and it occurs in plagioclase and some other minerals (see below).

The textures and patterns that can be observed in thin sections of rocks using a petrographic microscope and not only beautiful but also aid in scientific investigation. For example, petrologists use microscopy to study things like the metamorphic and deformational history of rocks. Further, chemical analysis can be combined with mineral identification from thin sections to determine the environmental conditions under which igneous rocks form, which can be useful in understanding magmatic processes.

So whether you’re looking at a rock through a microscope or observing global patterns there’s always something beautiful and interesting to see.

Surely, many of you have read the short story “Rip Van Winkle” by the American author Washington Irving. If not, the story recounts a man named Rip Van Winkle falling asleep in the Catskill Mountains of New York for 20 years.

This weaving of mountains and sleep seems to be a common premise of the literary world – as well as other crafts like music and the visual arts. I imagine due to the serenity felt when gazing upon soft ridges, for example. However, when I think of the mountains of Arizona – near my home – little about them makes me think of sleep.

I wrote previously on how hiking and climbing in different regions makes for entirely different experiences. Now I’m going to discuss some of the geoscientific reasons for these variations, focussing first on what makes the “sleepy”-type mountains so gentle. I’ve chosen to create a series of posts that focus on what I feel impacts my experiences the most: topography, vegetative cover, and climate.

Starting with topography: it’s a pretty broad term but generally refers to the spatial arrangement of physical features in a landscape. There are many related characteristics of mountainous landscapes like relief, prominence, and elevation that are more specific, so I’ll define those here.

Elevation is height of a topographic feature relative to something else – usually the mean elevation of the surface of the oceans (mean sea level). Relief is the difference in elevations (between a high point and low point) within a landscape. This can be expressed numerically by subtracting the elevations of the lowest point in the landscape from the highest point in the landscape. The larger the difference in elevation, the higher the relief. Prominence is similar to relief in that it is a measure of relative elevations in a landscape; however, it refers specifically to the height of a particular feature (like a mountain) relative to the surrounding terrain. Therefore, a mountain with great prominence is much higher than the other features in the landscape surrounding it.

So when I think of the mountainous landscapes of my youth – the “sleepy mountains” of Appalachia, these factors like elevation, relief, and prominence typically take low values. In fact, the highest elevation in Virginia – the state in which I grew up – is at Mt. Rogers and is a mere 5,729 ft (1,746 m). In Arizona – where I live now – the highest elevation is at Humphrey’s Peak and is more than double the elevation of Mt. Rogers at 12,637 ft (3,852 m).

And while Virginia has a varied topography with a lot of changes in elevation (and therefore relief), the relief is still less dramatic than some of the world’s other mountainous regions. For example, the average relief in Teton Range of Wyoming is ~3,000 ft (~900 m) – and while there are examples of these kind of changes in elevations in some parts of the Appalachians, the overall relief is relatively low.

When it comes to prominence, I return to the examples of Mt. Rogers (Virginia) versus Humphrey’s Peak (Arizona). The prominence of Humphrey’s Peak (6,039 ft (1,841 m)) is more than double that of Mt. Rogers (2,449 ft (746 m)). That means that while you’re in for a challenging hike in either case attempting a summit of these peaks, Humphrey’s Peak is definitely going to be more difficult.

Another factor that impacts my experience while hiking is the climate and the vegetative cover present in the landscape. The Appalachian mountains – particularly the central region where I grew up – are very lush and heavily vegetated. This actually makes geological field work a little more difficult in this region because exposure to the bedrock is more limited! So in regions with more vegetation, the paths are more likely to be covered in dirt and the trees are more likely to offer shade. These factors lead to a more pleasant outdoor experience in my opinion.

So why is this the case, that the central Appalachians are “sleepy”? Simply put, the reason is that the Appalachian mountain ranges are relatively old. The major mountain building event that led to the most of the uplift forming the Appalachians began about 325 million years ago and the mountains that formed as a result have been eroding since. Not only does this play a role in reducing the overall elevation, relief, and prominence but also, because collisional orogenesis in the region has ceased, the area is said to be “tectonically quiescent” or inactive and therefore there has been ample time for the landscape to adjust and for large plants to root and grow.

So if you ever find yourself with the urge to take a long nap in the great outdoors (hopefully not as long as our friend Rip Van Winkle!) perhaps head on out the the central Appalachians and enjoy some gentle, sleepy mountains. Just beware of black bears!