Tuesday, October 11, 2016

Macroevolution - Terms and Linkages

A few years ago, I had taken a class called Macroevolution. During the class we read several seminal papers on the subject and discussed the implications of these topics. At the end of the class, we set up on the white board some of the principle topics in macroevolution. The discussion involved how the topics were linked and specifically what they could be/were linked to. The class ended with a bunch of evolutionary topics that were heavily interacting and influencing each other. 

I though this was fascinating and I ended up taking pictures of the board after we had finished the class. Below is a cleaned up version of that work session with the appropriate terminology defined and/or discussed below. Keep in mind that the interactions depicted in the diagram are not all of the possible interactions, they are just the most prevalent ones that we happened upon during our discussion. 

Macroevolutionary concepts. Click for a larger version.

 The descriptions and definitions below are taken or paraphrased directly from the source literature as cited.

Adaptation – Any change in the structure or functioning of successive generations of a population that makes it better suited to its environment. (Oxford Dictionary of Biology)

Burden - Evolutionary constraints caused by functional interdependency and maintained by internal selection or in other words hierarchically nested interdependence of characters within the organism (Schoch, 2010). Basically these are genes that are hard wired into the genome and passed down through generations that are really difficult, if not impossible, to get rid of. For instance, almost all tetrapods have four limbs since the first tetrapod.

Constructional Morphology – Phylogenetic, functional, and morphogenic constraints and their dynamic relationship which help to explain a variety of evolutionary phenomena such as sub-optimal structures, convergence, parallel evolution, channeled evolutionary pathways, and the geometrical patterns that characterize organic structure (Reif et al, 1985).

Deep Homology – the sharing of the genetic regulatory apparatus that is used to build morphologically and phylogenetically disparate animal features. Homology, as classically defined, refers to a historical continuity in which morphological features in related species are similar in pattern or form because they evolved from a corresponding structure in a common ancestor. Deep homology also implies a historical continuity, but in this case the continuity may not be so evident in particular morphologies; it lies in the complex regulatory circuitry inherited from a common ancestor (Shubin et al, 2009).

Developmental Constraint – The theory that during development the systems within an individual organism will develop a limited and discrete subset of phenotypes, regardless of the environmental variance or experimental manipulation. In other words, regularities and trends observed in phylogeny are a reflection of a conserved set of pattern-generating rules. These internal rules of development define the realm of possible variation and place limits on the process of adaptation (Alberch, 1989).

Disparity (Morphological Disparity) – The total amount of the dissimilarities among all and any kinds of biological groups of organisms (Pavlinov, 2011).

Diversity (Taxonomic Diversity, Biodiversity) – The existence of a wide variety of species (species diversity) or other taxa of plants, animals, and microorganisms in a natural community or habitat, or of communities within a particular environment (ecological diversity), or of genetic variation within a species (genetic diversity). The maintenance of a high level of biodiversity is important for the stability of ecosystems (Oxford Dictionary of Biology).

Exaptation – A morphological or physiological character that predisposes an organism to adapt to a changed environment or lifestyle. (Oxford Dictionary of Biology)

Extinction Rate – The number of extinctions during a given period of time.

Gradualism (Phyletic Gradualism) - It holds that new species arise from the slow and steady transformation of entire populations. Under its influence we seek unbroken fossil series linking two forms by insensible gradation as the only complete mirror of Darwinian processes; we ascribe all breaks to imperfections in the record (Eldredge and Gould, 1972).

GRNs (Gene Regulatory Network) – GRNs are large networks that determine the course of animal development. These networks consist largely of the functional linkages among regulatory genes that produce transcription factors and their target cis-regulatory modules in other regulatory genes, together with genes that express spatially important signaling components. They have a modular structure, consisting of assemblies of multigenic subcircuits of various forms. Each such subcircuit performs a distinct regulatory function in the process of development. GRNs have been attributed to being the reason why there is little change in the phylum and superphylum-level body plans since the Early Cambrian (Davidson and Erwin, 2006).

Mass Extinctions – The extinction of a large number of species within a relatively short interval of the geological time scale. (Oxford Dictionary of Biology)

Natural Selection – The process that, according to Darwinism, brings about the evolution of new species of animals and plants. Darwin noted that the size of any population tends to remain constant despite the fact that more offspring are produced than are needed to maintain it. He also saw that variations existed between individuals of the population and concluded that disease, competition, and other forces acting on the population eliminated those individuals less well adapted to their environment. The survivors would pass on any heritable advantageous characteristics to their offspring and in time the composition of the population would change in adaptation to a changing environment. Over a long period of time this process could give rise to organisms so different from the original population that new species are formed. (Oxford Dictionary of Biology)

Punctuated Equilibrium – An evolution hypothesis that states in evolutionary history the development of new species occurs very rapidly in short bursts (lasting typically less than 100,000 years), which are separated by long periods in which little evolutionary change occurs (Oxford Dictionary of Science).

Red Queen Hypothesis – An evolutionary theory that describes how the coevolution of competing species creates a dynamic equilibrium, in which the probability of extinction remains fairly constant over time. Hence, evolution is seen neither as ‘progressive’ – with a species’ chances of survival improving over time – nor as ‘escalatory’ – with increasing vulnerability to extinction over time. Instead, as one species evolves improvements that make it more competitive, its competitors experience selection pressures that force them to evolve in order to keep pace with it. Ones that lag too far behind will become extinct (Oxford Dictionary of Biology).

Rock Record – The availability of the information on the fossil record, which is correlated with the availability of rocks during a particular time period. The absence or presence of rocks, which have the possibility of containing a set of fossils could have an influence on how scientists perceive the evolution of a particular group (evolutionary rate, extinction rate, diversity, etc.) (Barrett et al., 2009).

Signor-Lipps Effect – This effect is where for most organisms, it is unlikely that the true last occurrence of an extinct species or family will be recorded. Therefore, almost all observed time ranges are truncated. This causes a "smearing" of the record of an extinction event backward in time (Raup, 1986). In other words, a fundamental problem with using biostratigraphic last occurrences to infer patterns of extinction is that, barring reworking, last occurrences nearly always underestimate time of extinction. Signor and Lipps (1982) showed that a random distribution of errors at biostratigraphic range end-points can produce apparent gradual decline preceding a sudden extinction boundary (Meldahl, 1990).

Species Selection – Selection is one of two process of origination and persistence of clades that has been proposed. Selection encompasses those interactions between heritable, emergent character variation and the environment that cause differences in rates of birth or death among varying individuals (Vrba and Gould, 1986). Species selection requires that species be units of selection, and thus there must be properties of the species, rather than the sum of the properties of individuals, upon which selection can act (Erwin, 2000).

Species Sorting – Sorting is one of two process of origination and persistence of clades that has been proposed. In Darwinian Theory, evolutionary change is the product of sorting (differential birth and death among varying organisms within a population). Sorting is a simple description of differential representation; it contains, in itself, no statement about causes. As its core, Darwinism provides a theory for the causes of sorting- natural selection acting upon organisms in the “struggle for existence.” However, other processes (genetic drift, for example) produce sorting as well (Vrba and Gould, 1986).

Stasis – An evolutionary theory where there is zero rate of evolution and no extinction of speciation; evolutionary change occurs only in response to changes in the physical environment (Stenseth and Smith, 1984).

2008, in Hine, R. S., ed., Oxford Dictionary of Biology: Oxford, Oxford University Press.
2010, in Daintith, J., and Martin, E., eds., Oxford Dictionary of Science: Oxford, Oxford University Press.
Alberch, P., 1989, The logic of monsters: Evidence for internal constraint in development and evolution: Geobios, v. 22, no. Supplement 2, p. 21-57.
Barrett, P. M., McGowan, A. J., and Page, V., 2009, Dinosaur diversity and the rock record: Proceedings of the Royal Society of London. Series B: Biological Sciences, v. 10.1098/rspb.2009.0352, p. 1-8.
Davidson, E. H., and Erwin, D. H., 2006, Gene Regulatory Networks and the Evolution of Animal Body Plans: Science, v. 311, no. 5762, p. 796-800.
Eldredge, N., and Gould, S. J., 1972, Punctuated equilibria: An alternative to phylogenetic gradualism, in Schopf, T. J. M., ed., Models in Paleobiology: San Francisco, Freeman, Copper and Company, p. 82-115.
Erwin, D. H., 2000, Macroevolution is more than repeated rounds of microevolution: Evolution & Development, v. 2, no. 2, p. 78-84.
Meldahl, K. H., 1990, Sampling, species abundance, and the stratigraphic signature, of mass extinction: A test using Holocene tidal flat molluscs: Geology, v. 18, no. 9, p. 890-893.
Pavlinov, I. Y., 2011, Morphological Disparity: An Attempt to Widen and to Formalize the Concept, INTECH Open Access Publisher.
Raup, D. M., 1986, Biological extinction in earth history: Science, v. 231, no. 4745, p. 1528-1533.
Reif, W.-E., Thomas, R. D. K., and Fischer, M. S., 1985, Constructional morphology: The analysis of constraints in evolution dedicated to A. Seilacher in honour of his 60. birthday: Acta Biotheoretica, v. 34, no. 2, p. 233-248.
Schoch, R. R., 2010, Riedl's burden and the body plan: selection, constraint, and deep time: Journal of Experimental Zoology Part B: Molecular and Developmental Evolution, v. 314B, no. 1, p. 1-10.
Shubin, N., Tabin, C., and Carroll, S., 2009, Deep homology and the origins of evolutionary novelty: Nature, v. 457, no. 7231, p. 818-823.
Signor, P. W., III, and Lipps, J. H., 1982, Sampling bias, gradual extinction patterns and catastrophes in the fossil record Geological Society of America Special Paper, v. 190, p. 291-296.
Stenseth, N. C., and Smith, J. M., 1984, Coevolution in Ecosystems: Red Queen Evolution or Stasis?: Evolution, v. 38, no. 4, p. 870-880.
Vrba, E. S., and Gould, S. J., 1986, The Hierarchical Expansion of Sorting and Selection: Sorting and Selection Cannot Be Equated: Paleobiology, v. 12, no. 2, p. 217-228.

Tuesday, January 26, 2016

Geology of the National Parks in Pictures - City of Rocks

The next up on my Tour of the Geology of the National Parks in pictures is:

Our last stop on this trip through Idaho was the City of Rocks National Reserve. As always, you can click on the pictures to enlarge the images. At the City of Rocks, it is possible to travel through the whole park in essentially one loop, however you must leave the park on the western edge to get between the northern and southern roads of the park. We decided to take the southern road first, following the available Automobile Tour, then loop around to the northern road to finish the park.

 It has been a long trip, so I ended up not getting out of the car for this one. But snapped the picture as I drove by regardless.

During our trip we followed the "Automobile Tour" and my wife had read about each of the stops along the way. This is Circle Creek Basin. The main part of the rocks are from a 28 million year old granitic dome named the Almo Pluton, which is the lighter colored granitic rocks. The darker brownish-gray rocks are the Green Creek Complex (a complex mainly consisting of granite, granitic gneiss, and schist), which is 2-3 billion years old and are some of the oldest rocks in North America.

Treasure rock, where we let our daughter get out for the first time to "go play on the rocks".

View of the most prominent feature of the park, the Twin Sisters and Pinnacle Pass (on the left half of the photo). This is the pass through which the California Trail followed. The left twin is made up of Green Creek Complex, and the right is Almo Pluton.

Side view of the Twin Sisters focusing on the Green Creek Complex sister in the foreground. The other twin is actually directly behind the formation with only the tip of it peaking over the center of the photo. The outcrop on the left half in the background is not one of the twins (I think).

Dike through the Almo Pluton.

This was the last picture before having to leave the park on the western edge to complete our loop on the northern road. You can see the natural jointing of the rocks in the background lining up with the eroded arch in the foreground. 

A rock formation lovingly called the Bread Loaves showing more jointing in the granitic pluton. This is the first formation after we came back into the park on our loop.

The northern part of the part had a lot more rock formations than the southern part and in general was much prettier. If you can only do part of the park, I recommend this part. 

Here is Window Arch, which is probably the best hike in the park. Especially for people with a 5 year old who can't walk that far.

The pathway up to Window Arch, through the Almo Pluton.

Some nice jointing in the Window Arch area.

Back along the road, on our way out looking into the City of Rocks, where it indeed looks like a bunch of "buildings" sticking up out of the ground.

Thursday, January 14, 2016

Drunk on Geology - Dubhe

The next up in our Drunk on Geology series is Dubhe Imperial Black IPA right here from Uinta Brewery out of Salt Lake City, UT. 

Dubhe was a word that I saw on the package and I had to Google it to determine if it was a geological word or not and what I found I was rather surprised about. It turns out that Dubhe is the end star of the Big Dipper (as highlighted on the package). 

From their website: 

"Named Utah's Centennial Star in 1996, Dubhe (pronounced Doo-bee) illuminates the front of the big dipper from 124 light years away. Dubhe, also known as Alpha Ursae Majoris, is a red giant that appears orange in color and has a mass 4x that of the sun."

The word dubhe, is an Arabic word meaning bear, which is fitting since the Big Dipper is small part of the larger Ursa Major (or the Great Bear). Dubhe is one of the two stars that point towards the North Star.

Monday, December 21, 2015

Geology of the National Parks in Pictures - Hagerman Fossil Beds

The next up on my Tour of the Geology of the National Parks in pictures is:

As we continued our tour through southern Idaho, I really wanted to visit Hagerman, not the least because I am a paleontologist. Well, let me just get this out of the way first off, I saw no fossil localities, unlike at Dinosaur NM or Fossil Butte NM. This is more of a preserve to protect the fossils but they don't have the infrastructure (yet?) to allow the public access to see the actual dig sites. Hopefully that will come along sometime in the future. But as a paleontological National Park, this is the weakest one I have been to.

Me and my Gummy Bear doing our sign thing

 When we were planning on going to the park, I read everywhere that we had to go to the Visitor's Center first. Well this is the first thing that we noticed upon walking up to the door.

So as most any paleontologist is wont to do, we started digging to see what we could find.

Inside they also had a nice display full of fossils and other geological specimens for the kids to play with and analyze.

And they also had some of the more common mammal fossils.

Along with fossils found within the park too, like this lovely horse.

 And some elephantine specimens

After leaving the Visitor's Center there is one road with a couple of view spot's along it. This one describes the changing landscape from the Pliocene, when the fossils are from, to today.

There are also remnants of the Oregon Trail, as see here with the trail ruts.

And here you can see them really well on the left side of the photo where the road bends. 

The Snake River Plain, where Hagerman is located, is known for it's volcanic landscape. As the North American Plate traveled westward, the plate was dragged across the Yellowstone Hot Spot. The hot spot melted a swath through the Idaho countryside that left a significant mark on the landscape. The remnants of the old shield volcanoes and lava flows are pervasive throughout the region, as is described in this display.

Wednesday, December 02, 2015

Drunk on Geology - Black Butte Porter

The next up in our Drunk on Geology series is Black Butte Porter from Deschutes Brewery out of Bend, OR. (Also home to the Obsidian Stout and the Inversion IPA)

Although "butte" is a generic geological term for an isolated mountain jutting out of the landscape (dictionary.com), Black Butte is a specific mountain located within Oregon.

Location of Black Butte, Oregon.

Here is the geology of Black Butte from the Oregon.com webpage:
As you drive toward the flats of Central Oregon toward this symmetrical volcano, you might well wonder why it erupted here. The more famous High Cascades peaks formed along a fault that has been leaking lava for millions of years. But Black Butte grew along a different, parallel crack to the east. This fault also uplifted Green Ridge's scarp to the north, leaving the Metolius Valley as a long trough. 
Black Butte began to erupt quite recently, perhaps only 20,000 years ago. It quickly built up a 3,000-foot pile of cinders, one of the tallest such cones in the state. The eruption also buried the Metoilius River, creating Black Butte Ranch's swampy meadows on one side of the mountain and Metolius Springs on the other, where the river now emerges.
I can not find much information on the volcano, besides what is on Wikipedia.com (and we all know how accurate that can be at times).  However, with that being said, this is what I can glean from them. Black Butte is a shield volcano that is approximately 1.4 million years old (in stark contrast to what the Oregon.com page states). It is an extinct volcano, which I am inclined to agree with, since there is very little information about it and it is not listed on the USGS's list of volcanoes, which lists all of the volcanoes that have erupted in the last 10,000 years.

Besides that, Wikipedia mentions that the primary rock is basaltic andesite. This makes sense since it is "Black" Butte and basaltic andesite is a very darkly colored rock, common to volcanoes.

Basaltic andesite from http://earthphysicsteaching.homestead.com/virtual_geology_museum_galleryc.html

The volcano is also artistically rendered on the bottle and the package.

A nice picture of the actual mountain from http://www.blackbutte.k12.or.us/ 

Some of the descriptive wording presented on the stem.

And the other side of the stem.

Glamour shot

Thursday, November 19, 2015

Geology Through Literature - Faust

The next up on my Geology Through Literature thread is Faust by J. W. Von Goethe. 
Having some talks with David from The History of Geology, I realize I may have missed some geological aspects of the story. That being said, here are the ones I have come across: 

Part Two: Act I
"MEPHISTOPHELES:      Wherever you go in this world there's always a shortage of something. It might be this, it might be that. Here it's money we're short of. Now you can't just pick up money from the floor. But there's nothing sunk so deep we con't get hold of it, if we use our wits. There's gold, coined and uncoined, under old walls or in the belly of the hills. And if you ask me who is to unearth it: An intelligent man using the brains that nature gave him."
Some good ole hard work and intelligence has helped many a geologist to find precious metals and other goodies that the earth has buried deep within it.

Part Two: Act II - Earthquakes
SIRENS:      The water came foaming back, but not in its old bed. The ground quaked, the flood piled up, the shore cracked and smoked. Let's away from here, all of us. This miracle's no good to anyone.    Away to the sea-festival, all you guests, where the glinting, trembling waves lightly lap the shore, and the moon shines double and wets us with its sacred dew. Life there is unconfined, and here - this fearful earthquake. The place is dreadful. No prudent man would stay. 
SEISMOS: (making noises under the earth)
     Another good shove. Another good heave with my shoulders. Then I'll be out and they'll all have to scatter. 
SPHINXES:      What a horrid vibration. What fearful tension in the air. Such a swaying and tottering and rocking this way and that. It's intolerable, it's monstrous. But we won't move, though hell itself breaks loose.      The ground's lifting like a vaulted roof, marvelous. It's the same old man, the same old greybeard, who made the island of Delos, pushed it up out of the sea to oblige a woman in travail.   Now straining and squeezing away untiringly with all his might, his arms tensed and his back bent like the giant Atlas, he's lifting the grass, the soil, the sand, and everything in the peaceful river-bed, and cutting a gap right across the quiet valley. He's like a colossal caryatid, still buried below the waist and holding up a huge mass of rock. But this is where he stops, because we're here. 
SEISMOS:      I managed this all by myself. You'll have to admit it. And if I hadn't done so much shoving and shaking, how would it have been with this lovely world? You'd never have had your mountains towering aloft against the blue sky in its purity and splendour if I hadn't thrust them up for your pleasure, showing off in front of our great ancestors, Chaos and Old Night, and in company with the titans tossing Pelion and Ossa about like playthings. We carried on this way in youthful exuberance till we got tired of it and wickedly clapped the two mountains on top of Parnassus as a double night-cap...Apollo sojourns happily there with his muses. And who was it but me that planted the throne on high for Jupiter and his thunderbolts? Now once more I've force my way with an immense effort out of the bowels of the earth and call for happy settlers to begin a new life here."
In the first part of the section, I believe they are referring to an earthquake triggering a tsunami. "The water came foaming back, but not in its old bed." Tsunamis are frequent with earthquakes, especially earthquakes with their epicenter's under the ocean. Depending on the type of earthquake, what sometimes occurs is that during the initial ground movement, the ocean floor drops down, then quickly bounces back up. This sudden water displacement is one method in which a tsunami can be set in motion (nasa.gov).

The next part refers to the earthquake lifting land out of the sea, such as had happened with the island of Delos. Land being shifted upwards due to fault displacement is nowhere near an unheard of thing. As you can see in Chile, the coastline was uplifted during the 8.8 earthquake a few years ago, creating a new coastline. Since many earthquakes affect land not associated with a coastline it was difficult to determine relative changes in elevation, especially beneath the ocean. However, with modern GPS and other analytical methods, it is much easier and quicker to determine precise earthquake displacements not associated with a constant, like sea level, such as the rise in the ocean floor after the 2011 Japanese Earthquake.

Location of Delos, Greece
Has this happened in Greece though, specifically the island of Delos? Greece is far from a tectonically inactive area. They have been known to have earthquakes all through recorded history, however Delos sits in an area or relative stability compared with surrounding areas. In actuality, over the past few thousand years Delos has fluctuated up and down, with an overall subsiding trend. This fluctuation is likely what made it seem like Delos has remained stable through time (Pavlopoulos et al., 2011). So, even though it is stated that Delos was pushed out of the sea, it is more likely that Delos has always been out of the sea (during recorded history) and is currently slowly making it's way back.

Figure 5 from Pavlopoulos et al. (2011) showing that the area surrounding Delos is relatively stable, with Delos in particular subsiding over time. 

Part Two: Act II - Rocks
"ANAXAGORAS to Thales:
     Will that rigid mind of yours never relent? What more is needed to convince you?
     Water yields to any wind, but it keeps away from the sharp rock.
     This rock was made by explosion, by fire.
     Life began in the wet.
HOMUNCULUS between the two:
     Let me go with you. I also want to begin.
     Tell me, Thales, did you ever, in one night, make a mountain out of mud?
     Nature, the flow of nature, never depended on hours and days. She lets every form grow under her control. Even on a big scale there's no violence.
     But there was violence here. Cruel, plutonic fire, the tremendous bursting of aeolian vapous, broke through the old flat crust, so that at once a mountain had to arise.
     What does it help? What does it lead to? The mountain's there. So far, so good. This sort of argument's a waste of time. It only leads people by the nose, if they let it.
     The mountain's already alive with myrmidons, occupying the cracks. Ants and pygmies and other little busy-bodies."
The first part brings up the point "Life began in the wet". It is pretty well assumed that life did indeed first evolve in the water, due to the need for a transportation medium between adjacent components. Current research indicates that these components needed for life could have been brought in by the comet bombardment that saturated Earth in the early days (Sciencemag.org).

The second part that I would like to address was the violence of the plutonic fire as it broke through the flat crust. What is being described here is the violence often associated with volcanic eruptions, especially explosive ones. The mountain building being described I take as the accumulation of lava on the surface to produce land, where there once was none.

On a related note, there is a rather interesting story about the cinder cone volcano, Parícutin, that arose in a farmer's corn field in Mexico. Over the course of the first 4 months since it's initial eruption, the volcano went from nothing to 200 meters tall. This continued and is currently 424 meters high (Smithsonian National Museum of Natural History).

So, it is possible for a mountain to rise from nothing over a very short span of time. The number of earthquakes associated with the rise of Parícutin also increased exponentially immediately before the beginnings of the volcano. Perhaps Seismos had something to do with this one.

Pavlopoulos, K., Kapsimalis, V., Theodorakopoulou, K., and Panagiotopoulos, I. P. 2011. Vertical 
       displacement trends in the Aegean coastal zone (NE Mediterranean) during the Holocene 
       assessed by geo-archaeological data. The Holocene. v. 22 no. 6. pp. 717-728.

Tuesday, September 29, 2015

Geology of the National Parks in Pictures - Minidoka NHS

The next up on my Tour of the Geology of the National Parks in pictures is:

The Minidoka National Historic Site was the place of one of the former Japanese "internment camps" that was erected during World War II. Although, not a geological park there are some geological elements to the park.

 My lovely daughter presenting our NP sign.

Some background information on the Relocation Center.

 One of the few remaining original structures. The building materials for these structures was almost exclusively the local vescular basalt (basalt with a lot of holes in it). The basalt was formed in the Snake River Plane when the Yellowstone Hot Spot (volcano) was located within Idaho. The hot spot hasn't actually moved, but the North American plate has moved westward across the hot spot, creating this volcanic valley through Idaho, now known as the Snake River Plain.  

A close up view of one of the vesicular basalt blocks.

 View of the Internment Camp fence with the nearby Clover Creek running alongside it. Clover Creek is a tributary of the Snake River. The residents of the internment camp created a pool out of the water from the creek since the creek itself was too fast to allow for safe swimming.

Panoramic shot of  the park and the region along one of the park trails. Mostly flat within the Snake River plain. Footprints of the former buildings are visible along the way.

Tuesday, September 22, 2015

Drunk on Geology - Obsidian Stout

The next up in our Drunk on Geology series is Obsidian Stout from Deschutes Brewery out of Bend, OR.

Obsidian is a shiny, very smooth, and (often) black igneous rock. It forms from the extremely quick cooling of lava, where no crystals have time to grow. This creates a glassy structure, where edges are able to sharpened to be sharper than a razor blade. Obsidian is found in areas of former or active volcanism, much like along the Northwestern US with the active Cascade Range volcanoes (where Bend, OR is located). Surrounding Bend, there is also the Lava Lands Visitor Center and the Newberry National Volcanic Monument

Some actual obsidian.

Obsidian Stout

"Deep, robust and richly rewarding, roasted malt and black barley give way to notes of chocolate and espresso. Smooth and black as the glassy volcanic rock fields it's names for."

 "Give in to the deep, dark spell as the layers unfold."

Some lovely obsidian layers courtesy of  Lockwood (Outside the Interzone)

Glamour shot