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The logo sure does sound official, doesn't it? Well, given the diaries posted thus far, all of which explain some essentials of geology, including the larger tri-series on the Colorado Plateau, I thought today we would take a field trip together and I can learn the community about geology and some of you can teach me something about correct grammar. Deal?

And following up on rather singular diary posted this past week (on Ethnobotany). . .as the saying goes, "And now for something completely different!" That being said I think this Geology 101 class underway is unavoidable. What I mean is in the sense of going into more detail given the various geologic settings thus far discussed in this tour. Thus a more proper geologic explanation entirely focused on this academic discipline. On the other hand, what follows is a rather informal overview of the essentials of geology, and once gleaned, will help make it easier to tell one basic rock type or group from another (including making better sense of conglomerate formations defining the overall geologic setting).

Additionally, this diary's broad subject matter adds to a data base and will be helpful for all the diaries still to come. For those of you, like me, who sort of have rocks in your head, now you can at least shake 'em out and identify what lands on the ground and at your feet.

(Continues after the fold.)

The Colorado Plateau is rock heaven and a haven for those who especially love geology and the various rock formations on display. Rocks are also divided into three basic families. Each is based on how they form. Geologists classify all rocks on the planets in these three categories:

    IGNEOUS
    SEDIMENTARY
    METAMORPHIC

Let's start with the planet's original building block material, igneous rocks. If you found this sample lying on the ground. . .

Which is obsidian (or volcanic glass), then you would surmise it came from this hotter-than-Hades source. . .

The sample is also just one of many different types of igneous rocks.

Igneous rocks form from a melt, or magma, deep within the planet. Such rocks can be extrusive (volcanic) in origin, or else intrusive (still volcanic). Geologists place intrusive rocks in two categories: hypabyssal (meaning, igneous rocks derived from magma that has solidified at shallow depths in the form of dykes and sills of intrusions) and plutonic (meaning, material that is formed deep in mountain-building zones). Plutonic rocks are formed by partial fusion of lower continental crust and some from magma rising from the mantle. Slow cooling yields large mineral crystals, which are coarse-textured rocks (granite, diorite, gabbro, and peridotite). Granite, mainly that which is made of quartz, feldspar, and mica, is the main igneous rock of continental crust.

By contrast, hypabyssal rocks are relatively smaller masses, often strips or sheets. They cool at a lesser depth and much faster than plutonic rock. They are therrefore comprised of smaller crystals (microgranite, microdiorite, and diabase).

All intrusive rocks produce the following features:

     1) Batholith (a huge deep-seated, dome-shaped intrusion, usually of acid igneous rock).
     2) Stock (similar to a batholith but smaller; also have an irregular surface area under forty square miles or thereabouts).
     3) Sill (a sheet of usually basic igneous rock intruded horizontally between rock layers).
     4) Laccolith (a lens-shaped usually acidic igneous intrusion that domes overlying strata).
     5) Lopolith (a saucer-shaped intrusion between rock strata; up to hundreds of miles across).

With respect to extrusive igneous rocks, these occur mainly at volcanic vents along the active margins of lithospheric plates. Magma erupts as lava, which cools and hardens quickly on the surface as fine-grained or glassy rock (i.e., obsidian). When the magma hits cold water or land, it cools and crystallizes very quickly. Consequently, such rocks leave little or no time for the mineral crystals in the rock to grow to a very large size. Sometimes they cool so quickly that gases from the magma are trapped in the rock, forming gas bubbles, also known as vesicles. These small holes are also plainly visible when the final product is through. Examples of the most common volcanic rock types are: basalt, andesite and rhyolite.

(FYI: All basic lavas are rich in metallic elements but poor in silica. These lavas flow easily and erupt relatively gently. Basalt is the most famous kind of magma, which accounts for more than ninety per cent of all volcanic rock. Basalt is also formed by partial melting of peridotite, the chief rock of the upper mantle. Welling up from oceanic spreading ridges, the basalt builds new ocean floor material. There are also acid (i.e., silica-rich) extrusive lava flows. These appear at destructive plate margins. They probably comprise selected substances from basic lava of the upper mantle or reprocessed crust. Acid lavas are therefore explosive and slow-flowing. They produce such rocks as dacite, rhyolite, and obsidian.)

The igneous rock contribution to the planet's geophysical transformation is, of course, magma that has to go somewhere, that is, it occurs where heat melts parts of the Earth'€™s upper mantle and lower crust. Most magma that has cooled and solidified escaped up through the crust from oceanic spreading ridges. Smaller quantities came from destructive plate boundaries, colliding continents, and hot spots.

In addition to the main magma release there are intermediate lavas in the group, which contain plagioclase, feldspar, and amphibole. Alkali feldspar and quartz are also found in this group. The intermediate lavas stem from partial melting of certain minerals in subducted oceanic crust. Amazingly, some 860 known volcanoes have erupted in the last 2000 years. Those that emit continuously or periodically are considered active. Volcanoes that don’t erupt in recent times are labeled dormant. Long-inactive volcanoes are said to be extinct.

One more thing to mention here, and that is how the cooling process of both extrusive and intrusive rocks is important to note for this specific reason: as the magma cools the chemical elements in the material begin to join together in crystalline forms or minerals. As magma cools, it also crystallizes and turns into solid rock. The time it takes for some of these rocks to cool may take minutes, years, or even hundreds of thousands of years.

Perhaps with this above explanation this chart may make it easier to understand the nature of igneous rocks:

Contrasting igneous fire rocks with sedimentary materials, the latter are the easiest to understand.

Sedimentary rocks also form at the Earth's surface. Unlike igneous or some metamorphic rocks, their geologic clocks are not reset. This means they are not changed or altered from their original constituent properties as are igneous and metamorphic rock types. Primary sedimentary rock examples are limestone, sandstone, shale, and conglomerate. These softer rocks, as compared to the harder metamorphic rocks, are mostly what makes up the formations of the Grand Canyon’s upper walls, the horizontally-placed strata. Limestones are rich in calcium and magnesium carbonates. They make up about eight per cent of all sedimentary rock; only shale and sandstone are more plentiful. Organic limestones also contain calcium carbonate extracted from seawater by plants and animals that used this compound for their protective shells. Thus limestone rocks include reef limestones built up from the stony skeletons of billions of coral polyps and algae inhabiting the beds of shallow seas. Coquina is a cemented mass of shelly debris. Chalk is a white, powdery, porous limestone comprising tiny shells of fossil microorganisms, drifting in the surface waters before they perished, then rained down on the bottom of the sea.

By contrast, sandstone is a common sedimentary rock composed primarily of particles of sand, with minor amounts of silt and clay. These particles are cemented together, mainly by trace amounts of calcite or silica. Sandstone accounts for eleven per cent of the sedimentary rocks on the planet.

Add to this list the smaller fragments. For example, mudstone, like siltstone, and shale, which are the very soft kind of sedimentary rocks. They are made of clay minerals of less than 0.004 mm diameter. Siltstone are rocks formed of particles 0.004 to 0.06 mm in diameter. Shale accounts for more than eighty percent of all sedimentary rock. Shale also indicates a low energy environment, where silt and mud settles. Thus the accumulation of silt and clay equals siltstone and mudstone, whichl ends up as shale in one form or another. Rivers, floodplains, coastal tidal flats, lagoons, even deeper water offshore environments are where you will find these sedimentary materials in the makeup. All three of these rock types, including similar fine-grained rocks of silt and clay, are easily split along their bedding planes. This is why these much softer sedimentary rocks are fragile and easy to break. All sedimentary rocks form in three ways:

    CLASTIC formed from pieces of preexisting rocks (i.e., Coconino Sandstone).
    ORGANIC formed from the accumulated shells or body parts of once living creatures (i.e., Kaibab Limestone).
    CHEMICAL formed when minerals precipitate directly out of water and later form rocks (i.e., Travertine, which comes from calcium carbonate).

The last class of rocks are metamorphic. These rocks arise from the transformation of existing rock types, in a process called metamorphism, which means "change in form." The original rock (called a "protolith") is subjected to heat (temperatures greater than 302 to 392 degrees Fahrenheit) and pressure (1500 bars), causing profound physical and/or chemical change. The protolith may be sedimentary rock, igneous rock or another older metamorphic rock.

Metamorphic rocks make up a large part of the Earth's crust and are classified by texture and by chemical and mineral assemblage (known as "metamorphic facies"). They may be formed simply by being deep beneath the planet's surface and subjected to extreme high temperatures, as well as great pressure of the rock layers above it. They can form from tectonic processes such as continental collisions, which cause horizontal pressure, friction and distortion. They are also formed when rock is heated up by the intrusion of hot molten rock called magma from the planet's interior. The study of metamorphic rocks exposed at the surface following erosion and uplift provides geologists with key information about the temperatures and pressures that occur at great depths within the planet's crust. Some examples of metamorphic rocks are gneiss, slate, marble, schist, and quartzite, including this other wide assortment:

There is much more information available on the Web concerning all three types of rock. However, what was just explained provides you with the gist of each rock type. Now see if you can identify what type of rock given each of these three samples:

                                       

If you came up with igneous, sedimentary and metamorphic, I'd say you just made my day and you done good! So. . .Amen and W-women, too!

Next, let's consider hold old rocks and formations are, that is, how geologists figure the various geologic ages. Although some of this information has previously been mentioned, here is a more in depth analysis, though still staying with the Geology 101 theme (you know, the K. I. S. concept by keeping it simple).

The Geologic Ages: Next thing to do is take a gander at the names and dates of formations, specifically how the geologic chapters are divided from large to smaller units: Eons, Eras, Periods, Epochs, and Ages. As an example in my other office where I've worked for many years, the Grand Canyon dates from around the Proterozoic Eon (2500 to 570 million years), which is a significant slice of time taken from the Precambrian Era. The canyon's next chapter covers the Paleozoic Era (roughly, 540 to 250 million years) and completes the existing rock record of the Grand Canyon. The Mesozoic and Cenozoic completes the rock chapter eras.

This geologic time chart keeps track of the aging process of the Earth, where the geologic designation, "my," refers to millions of years. A plus or minus factor is common in geological dating of most formations. For example, if the oldest Paleozoic period (i.e., the Cambrian) is dated roughly 540 my, though it might turn out the formation from this period happened anywhere from 535 or 565 my. So, don'€™t be alarmed if other texts state a different age for this period. To a geologist, what's a few million years here and there when assigning dates to rocks and formations?

CENOZOIC Era (Chapter V: Modern Age):

          Quaternary Period 2 my
          Tertiary Period 65- 2 my

MESOZOIC Era (Chapter IV: Middle Age):

          Cretaceous Period 145 - 65 my
          Jurassic Period 210 - 145 my
          Triassic Period 245 - 210 my

PALEOZOIC Era (Chapter III: Early Age):

          Permian Period 285 - 245 my
          Pennsylvanian Period 320 - 285 my
          Mississippian (or Carboniferous) Period 360 - 320 my
          Devonian Period 410 - 360 my
          Silurian Period 440  - 410 my
          Ordovician Period 505 - 440 my
          Cambrian Period 550 - 505 my

PROTEROZOIC Eon (Chapter II; Precambrian): 2,500 to 570 my

ARCHEAN Eon (Chapter I; "In the beginning"): 4,000 to 2,500 my

HADEAN Eon (the time of "Hades"): 4,600 to 4000 my

Geology 101 Rounds house, kindly note: the Paleozoic, Mesozoic, and Cenozoic Eras are also collectively referred to as the Phanerozoic Eon, which entails the much shorter segment of Earth’s recorded geologic record.

Now that you know something about the date of the formations you might as well learn more about the rock materials. This information is especially useful if you plan to hike into the canyon and impress your friends, or even yourself, with the kind of geologic canyon knowledge that most people don’t bother to learn.

Dating The Rocks: Sounds like that kind of a date for romance and such but actually it'€™s how rocks are dated. This information I think the community will find interesting, simply from the standpoint geologists really aren'€™t guessing about the extreme dates assigned to various eons, eras and periods. Rather, it's more like a very close approximation. In fact, the science of dating rocks is improving all the time. Pretty soon a geologist will be able to tell you the day of the week the rock was made. (Well, there'€™s always room for showmanship and boasting, right?)

Dendrochronology: This science is the study of dating tree rings that tells us how old the trees are, including valuable information about the climate and environment they grew in. Rocks can also be dated, though less accurately than the science of dendrochronology. Geologists, especially, view the planet'€™s age in billions of years. In fact, the present day figures for the life of the universe is something on the order of 15 billion years old, and the age of the Earth is somewhere to 4.4 billion years. Closer to home here on the Colorado Plateau, the Grand Canyon’s materials are around 2 billion years old. With respect to the metamorphic rocks down in the inner canyon gorge the clock of time begins somewhere between 1.7 and 1.8 billion years ago.

You can expect geologists to imply a give or take clause (i.e., a plus or minus factor of, say, between 25 to 50 million years either way) whenever dates are given for any given rock or formation. The posited dates for eras and periods of rock formations are, nonetheless, fairly reliable in the sense the established evidence used for €”the method of dating rocks €”is credible.

Geology relies on several means to determine the age of rocks, formations, and geologic events. The scientific procedures used determine the various chapters, eras, and periods of the Earth's geologic history. There are a few procedures that denote both the main chapters and their secondary or tertiary units. Nevertheless, what’s ultimately determined is not explicit.

The subsequent information is about the dating techniques geologists are comfortable working with, starting with this proviso. Geochronology applies relative and absolute dating means to determine the age of rocks. Relative dating allows geologists to know if a rock is older or younger, but does not denote an actual age in years. Absolute dating, however, tells us an age in years.

When it comes to geochronology, these are the four relative dating techniques used today:

The Principle of Superposition refers to any undisturbed sequence of sedimentary strata, where the oldest layers will always be at the bottom.
The Principle of Cross-Cutting Relationships€ applies whenever some geologic feature cuts across or into a rock. Whatever is cut must be younger than what is being cut. Igneous intrusions and faults are two classic examples of this principle.

The strong>Principle of Inclusions applies where one rock has inclusions of an adjacent rock in its makeup. The inclusions must therefore be older than the rock they are embedded inside.

The €œPrinciple of Faunal (or Biologic) Succession is where life forms that correlate to the age of the Earth are unique to that, and only that, particular period of time. Thus fossils will be found in the rocks that correlate to a particular age.

With respect to absolute dating techniques its science was discovered in the early twentieth century. Therefore, it's the youngest method used to dates rocks. When radioactivity was discovered, science jumped forward in leaps and bounds. Suddenly, there was an extraordinary revolution in the earth sciences. Radiometric analysis€ bases its findings on, what is called, the half life of radioactive isotopes. Radioactive isotopes are unstable forms of particular chemical elements, whereby the isotopes are prone to decay, or else turn into something else more stable. To think of it another way, there are clocks in the rocks and radiometric analysis is a reliable means to determine when the clock was set, that is, the age factor.

These are the three common radiometric dating techniques that apply to this science and based on a process called nuclear fission:

1) Potassium-argon dating exploits the decay of potassium-40 isotope into another isotope called argon-40. This application is mainly used for igneous and metamorphic rocks of any age greater than about 1 million years, also sedimentary rocks containing the mineral glauconite (i.e., Bright Angel shale).

2) Rubidium-strontium dating uses the decay of rubidium-87 to strontium-87. This application is used for igneous and metamorphic rocks, but not basic types. Also, sedimentary rocks that contain the mineral illite (i.e., found in the mineral classification of silicates). This method is compatible for rocks more than 30 million years old.

3) Uranium-thorium-lead methods involve radioactive isotopes in uranium. Uranium-235 decays to lead-207 and thorium-232 decays to lead-208. This application is used for igneous intrusions, metamorphic rocks, and sediments containing Zircon. This method is best used for rocks over 100 million years old.

There is also a radiometric dating process used for fission-track dating. This application involves counting fission tracks produced in rocks by splitting nuclei of uranium-238, whose nuclei split at a known and constant rate. The older the rock, the more fission tracks there are. This method is compatible with many igneous and metamorphic rock types.

One other fairly recent method used to determine the age of rocks is called paleomagnetic dating, which uses the Earth'€™s magnetic field in prehistoric times to help date certain rocks. Scientists discovered the Earth is less a huge bar magnet, as was previously thought or assumed, than it is a self-exciting dynamo. Inside the planet radioactive heat keeps streams of molten metal flowing through the outer core. This is the process that generates electric currents, which then produce strong magnetic fields. As the Earth spins around its axis, it naturally directs currents and creates the magnetic poles. Powerful eddies in the currents most likely account for the magnetic pole's slight shift (i.e., the position) from year to year. Hundreds of reversals of polarity have occurred throughout the Earth'€™s history, which are still baffling to scientists to determine just how this happens. Nevertheless, some rocks retain a record of the Earth's polarity at the time those rocks were formed. Hence, the inherent value in paleomagnetism.

See if this chart makes sense to you:

Although determining the age of the rocks is fairly reliable using any of these means at our disposal, no procedure is accurate to the point geologists are able to determine the exact age of rocks. Nevertheless, geologists are able to piece together a sequence of rock strata anywhere on the planet and determine a uniform geologic time scale. In short, geologists have a reliable calendar at this disposal. This calendar therefore divides Earth'€™s history into increments based on appearance, or in some cases, the disappearance of certain fossils, also the existence of particular rock strata.

Before specifying the age of the Grand Canyon'€™s formations, here are two other methods used to date such materials:

1) Carbon-14 dating uses organic material and will only date back to about 50,000 years. This method is less useful to geology, although highly relied on when it comes to archeology and paleo-lithic history. Carbon-14 also decays rather rapidly and is useful for sedimentary rocks laid down (i.e., within the last 50,000 years or so), including dating archeological remains such as bone fragments and charcoal from campfires found in paleo-Indian sites.

2) Biostratigraphy is often used to date sedimentary rock formations, because this rock type is not compatible with radiometric dating. Biostratigraphy uses fossils to recognize the age of a sedimentary unit. Fossils offer valuable aids to relatively dating sedimentary rocks and are often juxtaposed with igneous intrusions and layers that can be dated. These dates are then applied to the fossils found in the rocks, which are then compared to other fossils around the world that are found in similar aged rocks. This is the kind of cross-study diagram that brings life to this science (and, of course, makes sense for those who focus on this particular discipline):

Biostratigraphy therefore involves identifying faunal zones, which are rock strata containing unique assemblages of fossils. Geologists also name each faunal zone after a distinctive species called a 'zone fossil.

However, such fossil correlation should first meet four basic requirements to determine a more accurate date:

    • the species was extremely plentiful;
    • it spread far and fast (i.e., planktonic organisms);
    • it left readily preserved remains;
     • then soon died out, which limited the fossil to a few rock layers.

Most of these organisms also lived in the sea and ranged from sizable animals (i.e., macrofossil) and plants to tiny forms (i.e., microfossil). Examples are: trilobites (i.e., three-lobed marine distant relatives of woodlice), ammonoids (i.e., cephalopod mollusks), bivalves (i.e., headless mollusks), and foraminiferans (i.e., small one-celled protozoan organisms).

Bear in mind there are always limits to our knowledge, especially where fossil creatures are concerned. Besides, most soft-bodied organisms left no fossil record. Relatively few land plants and animals were therefore ever fossilized. As it turned out, billions, perhaps trillions, of fossils completely vanished when erosion wore away the rocks that once imprisoned them, or else the fossils were baked or crushed by metamorphic changes. Consider, also, countless fossils are simply too inaccessible to reach and identify.

Well, I'm thinking it's about time for lunch or recess or maybe some of you folks headed down to the mull and do some shopping or people-watching. In other words, let's just say this diary's Geology 101 course has implanted something academic-related in your heads, which for future reference you can always refer back to this overview and background information (i.e., as a continuing data base series stored in my profile). Drop by any time for a review.

Tomorrow's diary will focus entirely on sedimentary rock formations, because we'll be headed for Zion National Park. Given the layout of this setting, it's difficult for some people to comprehend how a seemingly looking gentle stream (actually, the Virgin River) was able to cut down through some 2,000 feet of rock by which all else has followed. It's also the deepest chasm of its kind in North America when considering only one major geologic formation, the Navajo Sandstone, was exposed. Of course, natural and human history will also be part of the tour, not just geology.

As always, thoughtful commentary welcomed. (And, yes, sometimes I think learning science can be fun, at least interesting.)

Rich
http://www.nmstarg.com/...

Originally posted to richholtzin on Sat Feb 02, 2013 at 07:22 AM PST.

Also republished by SciTech, Backyard Science, and Community Spotlight.

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Comment Preferences

  •  Thanks Rich. (6+ / 0-)

    I have to leave now, but I will be back later this afternoon and read your diary. Hot listing it.

    I am a work in progress. Still.

    by broths on Sat Feb 02, 2013 at 07:27:21 AM PST

  •  Large volcanic eruptions are like a Rosetta stone (10+ / 0-)

    Absolute ages determined from volcanic layers are used as a time stamp on sedimentary layers and fossils. Generally there is an absolute age range determined. This helps geologists understand the connections between sedimentary formations separated by distance and geologic structure.

    For example, an ash layer from a super eruption at Yelowstone covered much of the U.S. That layer is a time stamp for the sediments around it.

    look for my eSci diary series Thursday evening.

    by FishOutofWater on Sat Feb 02, 2013 at 07:43:21 AM PST

    •  Thanks for the insight. . . (5+ / 0-)

      and we pretty do that sort of thing in this geologic part of the world and use absolute age-dating with absolute accuracy. Geology, the youngest of all Earth sciences, has certainly grown up in the past 50 or so years, huh? I think our last major volcanic event, as ash as lava flow, was Sunset Crater, just south of Flagstaff. That was about 950 years ago. Funny thing is, those 650 or so volcanic outlets breaking the crust throughout the Colorado Plateau are merely asleep; not dead. Looks like more ash volcanic layers still to come. Anyway, your point about comprehending with better clarity the connections between sedimentary formations and separation is well taken. Then again, if memory serves you have spent a lot of time in the field with a geologist's hammer and such. Any other comments on this elementary article you care to point out or add to. . .have at it, FishOutofWater. Most appreciated, too.

      Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

      by richholtzin on Sat Feb 02, 2013 at 09:21:43 AM PST

      [ Parent ]

  •  This will be my homework for the rest of the day (6+ / 0-)

    Thanks. I've been sorting my photos of Cambrian sandstone mineral patterns from my favorite Wisconsin nunatak.

    I love nature, science and my dogs.

    by Polly Syllabic on Sat Feb 02, 2013 at 07:45:58 AM PST

  •  Fantastic. (5+ / 0-)

    I have always been more into the life sciences. Over the last few days, though, I've been trying to learn more about the sedimentary layers of the Grand Canyon..  I understand that some YECs try to suggest that the rocks were laid down during the Noachian flood.  The Coconino is especially interesting in this regard as it doesn't even appear to be a marine deposit.  It is amusing to see the YECs fail as much at geology as they do at biology.

    If you don't mind, I'd like to republish this to Backyard Science a bit later.

    •  Thanks. . . (5+ / 0-)

      and how about contacting me on my profile's email and I'll bring you up to date on the geology of the Grand Canyon, my "other" office for many, many years. I am also going to some day soon prepare an entire week-long series on its subject matter, entitled 'THE TRAIL OF TIME,' which will give you and others in our illustrious community everything one ever wanted to know about this big ditch in northern Arizona (and quite a bit of stuff that may be a bit too much). So, thanks for posting your comment, billybush. Very much apprecited and you're onto something given your comments.

      Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

      by richholtzin on Sat Feb 02, 2013 at 09:12:05 AM PST

      [ Parent ]

    •  by the way. . . (1+ / 0-)
      Recommended by:
      billybush

      the only way to defeat a rapid inundation of the world by way of flood waters, and of course, basing same on a very young earth model of creation is to use a globe or a world map and point out continental plate configurations. I think you see where I could go with this, and just use the magic word, "Pangea," or the even older, "Rodina," and see if someone can talk you out of just how slow plates move, continental and oceanic. And I think this diary is reposted with Backyard Science, so thanks for doing that, if it was you who made the magic happen, billybush.

      P. S. No Noachian flood scenarios in my other office. Everything on top is straightforward sedimentary formations from the Paleozoic (with the Ordivician and Silurian periods missing), while below it's all Precambrian. I doubt Noah was around at the time unless he could live off of stramatolites for a diet.

      Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

      by richholtzin on Sat Feb 02, 2013 at 07:03:27 PM PST

      [ Parent ]

  •  Where does one sign up? (4+ / 0-)

    To the Department of Geological Sciences? LOL, I belong there :)

    Thank you! I am actually a leftover geologist from the 80´s of last century. When I was studyin it, Plate tectonics was still young(ish) and exciting. I still had professors that tried to tell us geosyncline terminology (which I hope has died out by now). You do everyone a service by posting material like this! One should know a bit about the land one lives on.

    What does this man with pistols do in the diary? Besides smiling very likeably, I mean, which of course is welcome :)

    You have so fantastic rocks over there. Give them a better example of a metamorphic rock. This one is a bit bland :)

    In fact if you want to do a series, that would be great. The wealth of stuff that modern geosciences can tell about near everything of Earth´s history and the formation of all the land is truly breathtaking. Especially if one shows exactly how people come to know the things they say: show them that that is not just tall tales: but the combination of real-world observations, solid understanding of chemistry and physics, and rational thinking.

    People who have learnt that are so much harder to embezzle with religulous or other ideological nonsense.

    my specialty was igneous and metamorphic petrology. So people can ask me things about that. They never do :)

    •  Geology 101 (1+ / 0-)
      Recommended by:
      maryabein

      Well, 201, actually.  At the ripe old age of 67, I've signed up for geology classes at Portland State U.  When you're over 65, you can take classes there for nothing, except book and lab fees.  There's no credit, but who cares?  I'm absolutely having a blast, going on field trips, and discovering that I'M NOT BRAIN DEAD after all!  Next term: Geology of the National Parks.  Woohoo!

      I keep thinking, wow, I wish I'd discovered this 40 years ago.  I'd have had a much different life than I did.  

      I'm still mad about Nixon.

      by J Orygun on Sat Feb 02, 2013 at 10:28:07 PM PST

      [ Parent ]

  •  Incredible diary, as usual Rich. I just have one (2+ / 0-)
    Recommended by:
    Polly Syllabic, homo neurotic

    question...why are you not writing a book??  

    •  Well, I am. . . (3+ / 0-)

      and thanks for posting another comment, another kudu, surelyujest. But I'm not anxious to get back on that road again, and so some of these diaries are extrapolated and edited from a larger work, FAMOUS LANDMARKS OF THE COLORADO PLATEAU, and I just want to get them out there and share with you and all the other good neighbors I have been introduced by joining Daily Kos (thanks to my good friend, Joe Maness, who guides me through our joint adventure The New Mexico Star Group (www.nmstarg.com), also posted on Daily Kos. Anyway, I am at the age that I want to give back some of what I have been honored to teach and share for many, many years, and even made a decent living doing it. Imagine getting paid to have fun and wear the body out (hiking and backpacking), which is at least better than rusting out, right? Anyway, I am happy to have met all of you and even more jazzed that folks find these diaries interested. Ergo, there will be more to come, starting with Zion NP tomorrow, Colorado Plateau People History (this coming Wed.), Canyonlands NP next Saturday and Desert Ecology the day after. So, you see I have my work cut out for me doing the re-edited versions, plus all the pics that some of you folks seem to enjoy. Anyway, thank you for the encouragement. I love doing this and find meaning doing so. Glad you and the others feel the same way.

      Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

      by richholtzin on Sat Feb 02, 2013 at 11:04:52 AM PST

      [ Parent ]

      •  Well it is certainly our great furtune to have (2+ / 0-)
        Recommended by:
        Polly Syllabic, homo neurotic

        you sharing your vast knowledge base and truly breathtaking photographs here.
        I do know a little bit about how fun a job that allows historical research and outdoor recreation is...I was a history interpreter at an historical park here in MI before I began raising a family (another lifetime ago). It was the most fun I ever had getting paid and every single day, even the challenging ones, were fulfilling.  My work was no where near as significant or scientific or physically challenging as your is, but it was prolific and beneficial.  I even started out as an Anthropology major/Archeology minor in college, but (no pun intended) that is all ancient history for me now.
        Thanks for contributing your fascinating experience and knowledge here with this community, Rich.  I always enjoy your posts very much.

        •  and on that note and comment. . . (3+ / 0-)

          surelyujest. . .what about a diary or two or three or more given what you used to do? I think people really need a break from the usual politico stuff that tends to egg people on, yet what does any of the process ever really do, except keep the discussions moving forward? I think the pundits in this community should quit writing and go to D.C. and take over Congress and run this country the way it should be run. These diarists certainly exemplify the brains and ethics and hutzpah to do the job. Like, TALK NEVER COOKS THE RICE, right? Anyway, I can dream, can't I? As for your interp job, it's always different regardless where you're teaching or what you're teaching. The trick is keeping your audience entertained, their minds full. . .and levity certainly doesn't hurt to sweeten the deal. I also once worked as an interp at something called Base Camp 1, but what a waste of my time and talents. Most of those people had the deer-in-the-headlamp stare as I discussed or interpreted this, that and the other thing, and I could just read their minds (". . .uh, when's lunch, dude?"). Not so with this eager-minded DKos community, n'est pas? Anyway, think about writing a diary given the passion and training and talent you once did before the family came along, because one of these days you just might return to that sinecure and it won't hurt to brush up now. Do you think? Thanks for posting your usual supportive commentary. Most appreciated.

          Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

          by richholtzin on Sat Feb 02, 2013 at 12:14:41 PM PST

          [ Parent ]

  •  This looks terrific.... (2+ / 0-)
    Recommended by:
    Polly Syllabic, homo neurotic

    I am hot listing it for reading tomorrow. A quick glance reveals that I am going to learn a lot! Thanks, Rich.

    •  hey there. . . (2+ / 0-)
      Recommended by:
      homo neurotic, Polly Syllabic

      and thanks, Don Enrique. . .not sure what you'll learn, but I am sure sometimes geology is a matter of unlearning. For example, knowing petrified logs from rocks and such. HA!. Anyway, I think it's a decent overview and doesn't get people too far over their heads, though it does put rocks in same. Then again, that's what geology's supposed to do, right? Thanks for posting (and take your time reading. . there'll be a quiz to follow. . .just kidding). Zion's coming out tomorrow, as well. I think most people will enjoy taking this tour, because it is so darn scenic there. All the best.

      Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

      by richholtzin on Sat Feb 02, 2013 at 12:08:41 PM PST

      [ Parent ]

  •  wow -- terrific! n/t (1+ / 0-)
    Recommended by:
    Polly Syllabic

    "i hear you're mad about brubeck ... i like your eyes. i like him too." -donald fagen

    by homo neurotic on Sat Feb 02, 2013 at 12:35:55 PM PST

    •  thanks. . . (0+ / 0-)

      and here I thought I just sent you a reply only to find it has vanished like loose dollars in my pocket. Well, I'll say it again, thanks for posting your comment and to earn a "terrific" for a primer on geology. . .that is quite a nifty compliment and I'll take and run with it. Gracias!

      Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

      by richholtzin on Sat Feb 02, 2013 at 06:55:57 PM PST

      [ Parent ]

  •  Diorites, Olivine and Schists, oh my. (2+ / 0-)
    Recommended by:
    Paulie200, Polly Syllabic

    I'll bet the tags were fun to do on this one! Now I want to go out and rock hunt like in my college days.

    Tell me a story of deep delight. - Robert Penn Warren

    by bisleybum on Sat Feb 02, 2013 at 12:58:43 PM PST

    •  HA! (1+ / 0-)
      Recommended by:
      Polly Syllabic

      the ole geology play on a theme from OZ. . .the Emerald City. . .and that's a rock. Yep, I like doing the tags but I never thought of the clever ones that you came up with. Of course, olivine is a pretty color green and diorite comes in fancy colors, too. . .especially in the Colorado Plateau's geology. Is that what you sort of have where you're living? And it's never to late to have a happy second childhood. . .so why not get out there do some rock hunting some more? I dare you! Thanks for posting your comment, bisleybum. I can see you have a good sense of humor. That counts in my line of work. . .or what I used to do all the time.

      Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

      by richholtzin on Sat Feb 02, 2013 at 02:50:26 PM PST

      [ Parent ]

    •  Rockhunting... (0+ / 0-)

      where the weight of the samples is directly proportional to the distance you have to carry them out.  

      Never "find" anything you don't want to carry  LOL!  Been there, done that, tore my T-shirt doing it!

      A celibate clergy is an especially good idea, because it tends to suppress any hereditary propensity toward fanaticism. -Carl Sagan

      by jo fish on Sat Feb 02, 2013 at 05:49:02 PM PST

      [ Parent ]

      •  and have you been in a. . . (1+ / 0-)
        Recommended by:
        jo fish

        national park lately, such as where I've been working for many years? God, the parkys frown on taking anything out of the Grand Canyon, especially, and you're right. . .never 'liberate' (my term for it, jo fish) you don't want to carry out. . .especially schist and granite objects. Thanks for the laugh and for commenting. Love the quote you use by Sagan. I met him a few times. . .he was a character!

        Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

        by richholtzin on Sat Feb 02, 2013 at 06:52:05 PM PST

        [ Parent ]

  •  And I might add... (1+ / 0-)
    Recommended by:
    Polly Syllabic

    I can see the way you've formatted and visually presented this as being conducive to an iPad app for home schooling or online credit, just sayin'.

    Tell me a story of deep delight. - Robert Penn Warren

    by bisleybum on Sat Feb 02, 2013 at 01:01:53 PM PST

    •  you stole my secret. . . (1+ / 0-)
      Recommended by:
      Polly Syllabic

      and you're right. . .bisleybum. . .the larger tome from which these diaries are taken, though re-edited (downsized) and the research stuff cut out. . .is intended for an apps life thereafter. I already have that strategy worked out, but I just don't seem to want to go down that road yet. I am having way too much enjoyment posting these missives for our community because the reception is so much better and I'm not worried about trying to make a deal or something. So, I'll get round2it (that other chore) one of these days. Meanwhile, more of these diaries to come. . .Zion NP for instance. . .up to bat tomorrow. Thanks for posting your comment and idea. We're thinking alike on same.

      Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

      by richholtzin on Sat Feb 02, 2013 at 02:47:22 PM PST

      [ Parent ]

  •  a gneiss diary.... ;) (5+ / 0-)

    -rimshot-

    (Hey... no heckling, somebody had to say it! I'm here all week.  Be sure to tip your waitstaff. )

    •  Now listen. . .Paulie200... (4+ / 0-)

      I think you're trying to take me for granite! There, tit for tat. And, of course, we both know gneiss is granite, only prettier, and formed under a lot more heat and pressure. And here's one I used to like to kid my students with, especially those who came from the East Coast. . .New Jersey is geneiss while New York is full of schist. Well, that's the typical geology respective to both states, right? OK. . .I'll quit on that one but I sure like your comment and appreciate the humor. And if I had a waitstaff you can bet I'd give them this tip: "Get out of the business. . .there's no money in it if you're working for me!" Opps, another groaner. Ain't life fun?

      Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

      by richholtzin on Sat Feb 02, 2013 at 02:41:54 PM PST

      [ Parent ]

      •  I should have known better than to get in (1+ / 0-)
        Recommended by:
        Polly Syllabic

        a pun fight with a professional!

        - ~~~~~~
        I               |
        I               |
        I~~~~~~!
        I
        I
        I

        Surrender Flag ;)

        •  you got me all 'rong. . . (1+ / 0-)
          Recommended by:
          Paulie200

          I just like puns. . .not an expert at it. But here's one for you (and you have to know what you're dealing with the upper layers of the Grand Canyon 'cake' to get this one Paulie200...what did the rock say to the passing sculptor on the way down to the Colorado River? "You wouldn't take me for granite, would you?" OK. . .no more of those. So give me some more material to work with here. . .puns and such. Like, old geologists never die. . .they just sorta erode away. Your turn.

          Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

          by richholtzin on Sat Feb 02, 2013 at 06:49:30 PM PST

          [ Parent ]

          •  What do u call a soda can found in a conglomerate? (0+ / 0-)

            Coca-Cola Clastic

            I cheated and looked that one up ;)  But it does bring up one of my favorite things geological to consider... what the clastic result of landfills will look like after the passage of geological time.  If sentient beings are around I bet it will be sought after for its beauty as counter tops when sliced and polished.

            An actual moment from my life last week... in line at the grocery store, scanning the headlines of the trashy pubs there, (inquiring minds want to know the latest on Lindsay Lohan and the Kardashians) and there is good old reliable Cosmopolitan, with the inevitable upper left hand corner tease about the months article about sex.... often exceptionally comical... and this one read...

            "Epic Sex Get it Give it or DO it Again..."

            I was thinking... "EPOCH sex? That's about how often I get any."   I thought about pointing to it and making the pun to the others in line... or the checker.  Alas... I kept it to myself... probably wisely.  :)

            •  Coca-Cola Clastic. . . (1+ / 0-)
              Recommended by:
              Paulie200

              now why didn't I think of that? But now I am and I will use it later for unsuspecting students in my care (the over 40s crowd, which is typical of the field institute folks who sign up for the tours, and the even older Roads Scholar students (formerly the Elderhostel program) which I am no longer leading those groups. Anyway, you bring up an interesting point: the landfill archaic stuff and what people in the future, supposing there will be a future, will one day utilize, as makeshift materials. As for what people typically gravitate to, as subject matter, please. . .let us not go into that. But I will say the reason I am happy here in the DKos community is there are diverse minds seeking diversified subject matter, and with the greater mix it's all good, even the seeming bad stuff. Thanks for posting your latest commentary, Paulie200. Zion NP awaits (if you tune into today's posting on same. . .around 9 am my time. . .mountain standard).

              Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

              by richholtzin on Sun Feb 03, 2013 at 06:36:13 AM PST

              [ Parent ]

  •  Excellent primer. n/t (1+ / 0-)
    Recommended by:
    Polly Syllabic

    "May the forces of evil become confused on the way to your house." - George Carlin

    by Most Awesome Nana on Sat Feb 02, 2013 at 01:41:59 PM PST

  •  Fun stuff, thanks! (2+ / 0-)
    Recommended by:
    Polly Syllabic, maryabein

    As an archaeologist, I do love some stratigraphy.

    Real stupidity beats artificial intelligence every time. (Terry Pratchett)

    by angry marmot on Sat Feb 02, 2013 at 03:06:49 PM PST

    •  Thanks, angry marmot. . . (2+ / 0-)
      Recommended by:
      angry marmot, maryabein

      for the kudus and citing what we both believe is (or can be) fun stuff. I guess you can say old geologist types never die...they just slowly erode away. As for archaeologists. . .I suspect that's where the term "fossil head" comes from??? I know my students used to call me that and here I was never a 'real' archeologist. Wished that I were (at times). Anyway, I'm thinking you love 'some stratigraphy' because. . .well, it's accuracy can be counted on and comparing samples is a bit easier this way. . .is that it? Anyway, thanks for posting your comment. Always good to have a good neighbor who's in your field. Both disciplines work rather well together, I say, and these years correlating geology with archeology is a given.

      Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

      by richholtzin on Sat Feb 02, 2013 at 04:37:29 PM PST

      [ Parent ]

      •  Heh... (0+ / 0-)

        I'm a stratigraphy nerd. Proper documentation of archaeological stratigraphy is fundamental for ascertaining the relative chronology of excavated loci (soils, fills, dumps, architecture, etc.). Some folks are in it for the "cool finds" but I geek-out most when pulling together a Harris Matrix.

        Real stupidity beats artificial intelligence every time. (Terry Pratchett)

        by angry marmot on Sun Feb 03, 2013 at 08:10:25 AM PST

        [ Parent ]

  •  Thanks for the primer. (0+ / 0-)

    "They come, they come To build a wall between us We know they won't win."--Crowded House, "Don't Dream It's Over."

    by Wildthumb on Sat Feb 02, 2013 at 04:46:01 PM PST

    •  and you are welcomed. . . (1+ / 0-)
      Recommended by:
      Wildthumb

      Wildthumb for the primer. One of these days a boost up to Geology specifics instead of just the essentials, what do you say? In other words, the stuff for rock hounds or wannabe rock hound types who know schist from that other stuff. Thanks for posting your comment.

      Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

      by richholtzin on Sat Feb 02, 2013 at 04:49:30 PM PST

      [ Parent ]

      •  Speaking of "schist," my one geological adventure (1+ / 0-)
        Recommended by:
        Trotskyrepublican

        of a couple of years back involved schist, "Catalina Schist" to be exact (the material making up the bedrock of Santa Catalina Island off the Southern California coast). I heard that there were few areas on the mainland containing this schist. I obtained some samples that I thought might be said schist on the mainland, and took them to a Geology professor at Cal State Long Beach. He identified them as Catalina Schist. They were bluish/greenish and looked layered.  Cool, huh? I wanted to include them as part of our Channel Islands section of our large school nature center.

        After my "expedition," I wanted to do more, but I'm more of a plant and critter guy than a rock guy, and have more of an amphibian expedition in mind next. But I always wanted to do a course on the local geology of Southern California.

        Keep informing us.

        "They come, they come To build a wall between us We know they won't win."--Crowded House, "Don't Dream It's Over."

        by Wildthumb on Sat Feb 02, 2013 at 08:45:06 PM PST

        [ Parent ]

        •  thanks for posting. . . (1+ / 0-)
          Recommended by:
          Wildthumb

          Wildthumb. And it may surprise you to know I am also a critter and plant guy, though I love it all. (Students used to call me 'Dr. Doolittle" because I was forever engaging with all creatures great and small. . .bobcats, snakes, scorps, badger, ringtail cats, wild turkeys. . .you name it and I was enthralled). Anyway, you're right. .  schist is layered. In fact, if you down into the Grand Canyon's basement rocks you will be looking back up at the Vishnu Mountain remnants, former 'black giants' that may have scratched the sky at some 20,000 feet above sea level. The schist is micaceous (lots of mica and biotite and such) and somewhat wavy due to plutonic dikes and sills of intrusions, especially with the Zororaster granite (so-called) was injected into the much older schist. Anyway, at the top of the mountain remnants, where erosion continues eating away at the exposed rocks (from above) you can see the lamination of the schist, like flakes compressed together, only coming apart. Indeed, a solid schist rock form, though quite heavy, is easily malleable when taking the flakes apart (once eroded). And a hands-on demonstration to students on this backpacking treks always amazes them how easily schist erodes, once exposed to the elements.

          Anyway, thanks for posting your comment and I hope to hear more from you given later diary offerings. Today's, for example, will be on the peerless Zion NP. Its exquisite Navajo Sandstone geology (the most predominant sandstone-sedimentary formation in the park) is highlighted in the geology phase of explanation.

          Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

          by richholtzin on Sun Feb 03, 2013 at 07:44:56 AM PST

          [ Parent ]

          •  Thanks, richholtzin. The schist I got was exposed (0+ / 0-)

            to creek action, so it looked more "congealed" and rounded and solid, though I could see crusting and layering.

            Will follow your articles. :)

            "They come, they come To build a wall between us We know they won't win."--Crowded House, "Don't Dream It's Over."

            by Wildthumb on Sun Feb 03, 2013 at 08:58:58 AM PST

            [ Parent ]

  •  On a geologically serious note, (0+ / 0-)

    my favorite geologic hunting grounds are the gneiss formations of the Laurentian shield on the eastern side of Georgian Bay. Glacially scoured ancient extrusions with stunning mineral veins. We have some pre-Cambrian bedrock on the eastern edge of the Smoky Mountains near where we live, and I still have some of my geology field guides, so I think when the weather warms up a little I'll be heading that way. I'm not the photographer you are, so you've got no competition here. Thanks for the inspiration.

    Tell me a story of deep delight. - Robert Penn Warren

    by bisleybum on Sat Feb 02, 2013 at 05:19:15 PM PST

    •  Your next field trip. . . (0+ / 0-)

      That Laurentian shield geology you folks have gone for you is mighty ancient stuff. I think the Canadian shield is far older, but if memory serves the rocks in your area are about 3.2 bya??? The Smokies are a great chain, and I think they are about as old as the Appalachians. That entire Atlantic Basin to the east is also fascinating geology (way down deep). Do me a favor.  . .and post me your geologic sleuthing when you do get out for a rock hounding excursion once again. I know my province, the Colorado, and the Basin and Range and the Rockies, but confess to an ignorance of other provinces, though I do have maps online to bring out the ignorance and gloss it over with some insight. We'll see if i get motivated to do it. Here's to Laurentia and I suppose that's something inside for geologists to know and appreciate; all that marvel of plate tectonics and such. Thanks, again, for posting a comment, bisleybum.

      Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

      by richholtzin on Sat Feb 02, 2013 at 06:46:20 PM PST

      [ Parent ]

      •  Will do. (0+ / 0-)

        Would you be more curious about the Smokies basement complex or the predominant Ordovician strata?

        Tell me a story of deep delight. - Robert Penn Warren

        by bisleybum on Sun Feb 03, 2013 at 06:33:50 AM PST

        [ Parent ]

        •  both. . . (0+ / 0-)

          I have some geology stuff already bookmarked about those inspiring mountains (since you first mentioned your appeal to its rock strata), but if you have something to share with me, I find both the basement complex rocks (something always interesting to me as a geologic base) and the Ordovician strata. As I said, or think I did, the Grand Canyon's Paleozoic Era's upper layers are the most complete exposure on the planet, yet we are missing both the Ordovician and Silurian, and a great deal of my favorite period's rocks, the Devonian. But there, however, you got it all. . .but it's not exposed to any great degree, I'm thinking.

          Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

          by richholtzin on Sun Feb 03, 2013 at 09:24:39 AM PST

          [ Parent ]

  •  Thanks for the diary! I used to be a geologist, (2+ / 0-)
    Recommended by:
    Trotskyrepublican, J Orygun

    studying sedimentary rocks to learn about the tectonic history of the eastern edge of the Mojave Desert.  I don't do that any more, but this diary brought back lots of memories.  It's incredibly beautiful country, even more spectacular when you know something about its history.  Science deniers don't understand how wonderful the workings of the real world/universe are - the more you know, the more amazing and awesome it all is.  I look forward to your e-book!

    •  Thank you. . . (0+ / 0-)

      kkbDIA. . .and how I wish you would write a diary and express what you just said. . .only in an expanded form! Yes, geology does reveal so much more when you know what you're looking at and why the layout is what it is. I, of course, look at science denialists as you put it, the way I do a child who refuses to learn something new. It's up to him or her to learn how to use the mind like a parachute. Otherwise, there's no sense debating people like this. It'd be like trying to have a good conversation with the likes of Glen Beck, only knowing the brain behind the face has long since calcified. Anyway, thank you so much for posting your comment. And what were you do on the eastern edge of the Mojave? I'm curious about your studies there. Send a reply to my profile email. I love that desert and taught geology in and around the Las Vegas area and Death Valley. Fascinating Basin and Range topography and the geology that done it all!!!

      Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

      by richholtzin on Sat Feb 02, 2013 at 06:40:44 PM PST

      [ Parent ]

  •  Thank you!! (0+ / 0-)

    This is the first of your diaries that I've seen, and I'm glad I came across it. Thank you for taking the time and effort to write it.

    •  and you are welcomed. . . (2+ / 0-)
      Recommended by:
      maryabein, niterobin

      niterobin. But let me also say it truly is because of people like you and this wonderful Dkos community that makes this all possible. While I am admonished by some others (outside the community) to publish this stuff. . .I'm just not in the mood. I'd rather while away the time sharing these tidbits of this, that and the other thing. I'll get around to doing final and presentable drafts to publishers one of these days. For now, let's have some fun and enjoyable reading away from the usual political and social diatribes/issues that keeps most people's attention. After all, there has to be something good in all this negativity that seems to encapsulate the essence of the 21st Century. Next up (today), Zion NP. I hope you'll join me and the others on the virtual armchair tour. Thanks, again, for posting your comment.

      Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

      by richholtzin on Sun Feb 03, 2013 at 06:30:36 AM PST

      [ Parent ]

  •  I live in the Pennyroyal area of KY. (0+ / 0-)

    The local rocks in my immediate area are St. Louis Limestone. I can sort of comprehend how limestone is formed, but I haven't been able to wrap my mind around how the numerous chert balls & chert layers are formed. Chert balls have a reddish outer layer and are slate gray to black on the inside. They must have been the raw materials for most local arrowheads. An outcrop in a sink on my farm has two continuous layers of black chert. Each is a few inches thick and the two bands are separated by a few inches of ordinary limestone. Apparently, conditions were very different during the timeframe the chert was being formed, but I don't understand in what way. Nor do I understand what the chert was before it was chert.

    •  Thanks for posting. . . (0+ / 0-)

      dot farmer. Chert is a natural precipitate out of limestone. Out here it is sometimes called "jasper" which is reddish, and favored long ago for arrow and spear tips. Anyway, what you're seeing, and may even be admiring, is au natural. (I used to live in Cincinnati (commuting to/from the Grand Canyon for my assignments) and noticed the same thing in Cincy's numerous limestone beds, its substratum of geologic rock). Technically, chert is a fine-grained, silica-rich microcrystalline sedimentary rock. (Lots of fossils in same, too.) It varies from white to black, and therefore grayish, brownish or a rusty red tincture is also common.) Incidentally, the color denotes trace elements present in the rock, both red and green, which are often related to traces of iron (i.e., respectively, oxidized and reduced elemental forms).

      One more thing you folks have a lot of back there and that is flint. Actually, this is also chert, only occurring as oval to somewhat irregular nodules in limestone (as well as chalk and dolostone formations. . .as a replacement mineral). This is where we (out here in the West) finds thin beds deposited, as jasper.

      So, yes, conditions are aberrant in a sense of what you have noticed. You must have a geologic streak in you to even notice such. I am betting that formation (or formations) is also richly loaded with fossils. Maybe you can take a picture and send what you're looking at to me at my profile's email. I have you say back in your neck of the woods is some of the prettiest limestone I've ever seen (in North America), while Italy goes a bit farther with its marble (a sort of metamorphosed limestone). In short, an outrageous display of form and beauty embedded in rocks from ancient seas.

      Hope my bit of chatty report was helpful, dot farmer. And thanks, again, for posting your commentary.

      Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

      by richholtzin on Sun Feb 03, 2013 at 07:36:36 AM PST

      [ Parent ]

  •  Rocks have uranium, thorium and lead in them? (0+ / 0-)

    They need to be banned.

    Just kidding.    Thanks for taking the time to produce an educational diary.   It's wonderful.

    •  What? And give the fossil fuel energy. . . (1+ / 0-)
      Recommended by:
      NNadir

      more opportunity to choke the atmosphere with greenhouse emissions? We need radiation and if the rocks can heat and light us up. . .let's support the issue. Just kidding too. Anyway, thanks for posting your comment, NNadir. I have always had a special love for rocks and this science and here I'm not even academically trained in the subject. Then again, what's 40 or so years of being an experiential rock hound and learning and teaching the subject? Today's posting is more rocks, sort of: Zion NP. Be sure and tune in. Navajo Sandstone is to die for, though not in that figurative sense.

      Treat the world (yourself, and others) as part of a living organism. Everyone and everything will benefit.

      by richholtzin on Sun Feb 03, 2013 at 06:26:58 AM PST

      [ Parent ]

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