June 2008

Rocky VI

Global warming — a hot time in the old town tonight.

Author’s note: The beautiful illustrations in this article are by Northern Arizona University’s Ron Blakey. For more illustrations of how the Earth evolved throughout time, go to his Web site at http://jan.ucc.nau.edu/~rcb7/globaltext2.html

Recent Carved In Stone articles have described the life of Rocky, a 1.8-billion-year-old rock from Morrison, Colo. Last month, this column described the childish antics of two paleontologists fighting about dinosaur bones in Rocky’s backyard. One of the dinosaurs discovered in Morrison was Apatosaurus, also popularly known as Brontosaurus (which, as any school kid will tell you, is incorrect).

Luckily for it and its friends, the climate in Colorado during Apatosaurus’s reign here was much different than the cool, dry, continental climate we have today. This is, in part, because the movement of continents over the Earth’s surface (referred to as plate tectonics) has a pronounced affect on its climate. As demonstrated in the series of photos accompanying this article, climatic changes due to plate tectonics take place throughout tens of millions of years. These long-term climate changes are not the same as the more rapid climate changes being debated by scientists in the present.

Let’s begin by looking at the Earth about 240 million years ago (during the Triassic Period). All the continents clumped together to form a supercontinent called Pangea. The large land mass extended nearly from pole to pole, severely disrupting the ocean currents. That fostered hot, arid, continental climates and the melting of the Polar ice caps. If you are wondering how ocean currents affect climate, just think of El Niño.

About 150 million years ago (during the Jurassic Period) when the Apatosaurus was here, North America was drifting away from Europe, and South America was just beginning to drift away from Africa. This opened a deep-water gateway across the equator (the Atlantic Ocean), which dramatically transformed oceanic currents and the climate. Morrison was wet, swampy, and warm.

The continents continued to drift apart, ocean currents modified their course and intensity, and the climate changed accordingly. About 90 million years ago (during the Cretaceous Period), global surface temperatures were about 18o F (10o C) warmer than those we have today. That is the hottest climatic period recorded in geologic history. Morrison, on the other hand, was at the bottom of a great interior seaway.

These illustrations demonstrate how the Earth’s climate has changed in response to the forces of plate tectonics. Climate has changed as the result of other natural forces such as asteroid impacts, changes in composition of the atmosphere, and ash and carbon dioxide from volcanoes. But that’s another story. 

May 2008

The Bone Wars

Near Rocky’s home is a formation that played host to one of the biggest battles of the Bone Wars.

Prologue: Recent Carved In Stone articles have described the life of Rocky, a 1.8-billion-year-old rock from Morrison, Colo. Looking east from the quarry where I found Rocky, I can see the outcropping of rocks named the Morrison Formation, host to one of the biggest battles of the Bone Wars.

Recently, my wife, Pam, and I were watching our grandkids at the park digging up some “dinosaur bones” buried in the sand. The play ultimately turned into a sand fight. Such is the way of siblings — and two pre-eminent paleontologists of their time — Edward Drinker Cope (1840-1897) and Othniel Charles Marsh (circa 1832-1899).

Cope, at age 18, wrote the first of approximately 1,400 scientific papers he would publish in his lifetime. He briefly attended the University of Pennsylvania, and studied abroad, but was largely a scientist by self-study.

Marsh, at age 21, inherited a dowry that his uncle provided for Marsh’s mother. His uncle also financed Marsh’s education at Yale College and awarded money to Yale for the Peabody Museum of Natural Sciences, which Marsh would manage.

Cope and Marsh met in 1863 while attending Berlin University. Cope became a professor at Haverford College in 1864; Marsh was made Professor of Paleontology at Yale in 1866. Cope left Haverford in 1867 to study fossils in the marl pits at Haddonfield, N.J., where the first American dinosaur had been unearthed. Cope and Marsh spent a week together exploring the fossils, and, unbeknownst to Cope, Marsh made a deal with the workers to sell any new fossils to him instead of Cope. This devious behavior typified their relationship.

The race to discover new dinosaur species began in 1870 when Marsh embarked on an expedition to the American West; Cope set out in 1871. They soon began exchanging heated letters.

New fossil localities were discovered; new battles erupted. In 1877, Professor Arthur Lakes from the Colorado School of Mines unknowingly stirred the pot when he wrote to Marsh about fossil bones he discovered in Morrison, Colo., (near Rocky’s home). Marsh did not reply, so Lakes sent some of the fossils to Cope. Learning what Lakes had done, Marsh sent $100 to Lakes who, in turn, asked Cope to send the bones on to his rival.

Marsh began collecting fossil bones discovered by railroad workers near Como Bluff, Wyo. Cope accused Marsh of trespassing and stealing fossils. Marsh had fossils destroyed rather than fall into Cope’s hands. Cope bought controlling interest in the journal, American Naturalist, so he could speed his articles into publication. Marsh salted Cope’s digs with bone fragments unrelated to the local fossils. Cope rerouted a trainload of Marsh’s fossils. Marsh used his influence to prevent Cope from obtaining accommodations at army forts. These are but a few examples of their many conflicts.

Their mutual loathing became public in January 1890 when the two combatants aired their differences in the New York Herald. Cope accused Marsh of stealing fossils and plagiarism. Marsh shot back that in 1869 Cope had erroneously placed the head on the tail end of an elasmosaurus skeleton. Ironically, Marsh had discretely pointed this out to Cope at that time, sparking the feud that lasted their lifetime.

Epilogue: The Bone Wars ended in 1897 with Cope’s death, but not before both had exhausted their fortunes. Prior to 1870, nine species of North American dinosaurs had been classified. Between 1870 and 1897, Cope and Marsh classified 136 new species, much of the time behaving like a couple of kids.

April 2008

Rocky IV

Tips and tricks for learning the inner secrets of rocks, but don’t tell Grammy!

Boy, am I in trouble now. Our grandkids, Donovan and Delaney, and their Mommy and Daddy, are visiting us. A couple of days ago, I showed the kids Rocky, my pet rock. Without thinking, I licked the surface of the rock so my saliva would enhance the color of the rock, and the kids could appreciate the pretty bands of different colored minerals that make Rocky a gneiss (pronounced nice). The bands consist of light-colored feldspars and quartz, and dark colored mica and amphiboles.

We have some gravel along the grassy areas in our yard where the dogs play. Next thing I knew, Donovan and Delaney were licking the rocks to see them change colors. Cool, except Grammy and Mommy were watching. 

Geologists do a number of things to learn the inner secrets of rocks. They lick them. They crack them open to see fresh mineral surfaces. They cut them and polish the surface, just like granite or marble countertops. They cut them into extremely thin slices that you can see through and look at them under special polarizing microscopes. They even coat them with a thin layer of gold and look at the surface under a scanning electron microscope (SEM). 

That is what you see in the accompanying SEM micrograph (see Figure 1- right). Mica, the main mineral in this SEM image, is in almost every mineral kit you can buy. You probably remember it as the mineral that can be split into sheets so thin that you can see through them. But if you thought you had split the mica into a single sheet, you were not even close.

This SEM micrograph is looking at the edge of some mica sheets from a very tiny part of a dark band of minerals on Rocky’s surface. From this view point, the mica sheets look like the edge of a stack of papers. The white bar at the top of the photograph is 20 microns long. To put that into perspective, a human hair has a diameter of about 70 microns. So the end of a human hair would completely cover this SEM micrograph.

Also in the micrograph are some grains of feldspar (with smooth sides) and quartz (the ragged grains) that are nestled between some of the mica sheets. Each mineral in this rock recrystallized at a specific temperature and pressure. For example, in the center left of the image, you can see where the mica sheets (which had already crystallized) were distorted by the feldspar crystal that recrystallized later, at a lower temperature and pressure than existed when the mica recrystallized.

But enough about Rocky’s inner secrets. I need to tell Donovan and Delaney that they should not lick rocks. They should spit on them. Do you think that will make Grammy and Mommy happy?

March 2008

Rocky III

When it comes to plate tectonics, dinosaurs help tell the story.

The recent Carved in Stone articles have talked about  Rocky — a 1.8-billion-year-old grey and pink banded metamorphic  rock referred to as “gneiss” (pronounced nice). Last month, we saw how Rocky wandered around the globe and learned how the  magnetic minerals in the rock  help geologists determine the  path he took. I also lamented  that my grand kids Donovan  (4 years old) and Delaney  (3 years old) probably do  not care much for magnetic  minerals or plate tectonics. Well, there  is more to the story. Here is something I  am sure the kids will like — dinosaurs!  

Between 248-206 million years ago,  South America, Africa, Antarctica,  India, and Australia were all clumped  together. As early as 1596, Dutch map  maker Abraham Ortelius suggested that  the Americas were “torn away from  Europe and Africa” and that “the vestiges  of the rupture reveal themselves,  if someone brings forward a map of the  world and considers carefully the coasts  of the three [continents].” Ortelius’ idea  resurfaced in 1858 when geographer  Antonio Snider-Pellegrini made a map  showing how the American and African  continents may have fit together.  

However, it was not until 1912 that  the movement of continents was given  serious consideration as a scientific theory.  Alfred Wegener, a German meteorologist,  proposed that the land masses  on the globe had been a single continent  and that they began to break apart  about 200 million years ago. His theory  was based, in part, on the remarkable  fit of the South American and African  continents. But Wegener  was intrigued by the occurrence  of unusual geologic  structures and fossils found  on matching coastlines of  a number of continents (as  shown on the accompanying  illustration), which are  now widely separated by  oceans. Cynognathus and  Lystrosaurus were land reptiles.  If they tried to swim  across the ocean they would  have sunk like a rock. Mesosaurus  was a freshwater  reptile and couldn’t swim  very far, certainly not  across the ocean. Glossopteris  — it was a fern with big heavy seeds that could not be blown across  the ocean. Wegener reasoned it was  impossible for these organisms to  traverse the great distances across the  oceans. To him, the fossils were the most compelling evidence that the  continents had once been joined.  

Scientists have used this evidence  to help develop the theory of plate  tectonics and reconstruct Rocky’s  journey across the globe. The next time Donovan or Delaney wear their dinosaur pajamas, I will tell them the  story of Cynognathus, Lystrosaurus,  and Mesosaurus.

Do you think they will like it?

February 2008

Rocky II

Forget Waldo, where in the world is Rocky? It depends on when you look.

During a recent visit to Phoenix, my grandkids, Donovan and Delaney, and I watched some ants wandering around on a great big leaf that was slowly drifting across a pond. I was tempted to point out how the ants and the leaf were analogous to people walking around on a continental plate that is slowly floating around the surface of the earth. I resisted the temptation because they are just kids who haven’t even started school yet. I figured they would like plates of cookies better than plate tectonics.

But, like it or not, plates of the earth’s crust are constantly on the move. Plates on either side of the East Pacific Rise, one of the fastest moving mid-ocean ridges, spread apart about 6 inches each year. North America and Eurasia spread apart along the Mid-Atlantic Ridge at a rate of about 1 inch per year. Now, this isn’t enough to explain the increase in airfares from New York to London, but throughout millions of years, things add up.

Last month, this column introduced Rocky, a grey and pink gneiss (layered metamorphic rock), which was rescued from a quarry near Morrison, Colo. His current location on earth can be recorded as 39º38'10" N latitude, 105º12'24" W longitude. But Rocky hasn’t always been at that location. The forces of plate tectonics have pushed Rocky’s home around the surface of globe for billions of years.

The three maps in Figure 1 show how the earth looks today and how it might have looked 300 million years ago (Ma) and 600 Ma. The grey dashed line shows the path of Rocky’s journey across the earth starting about 600 Ma. The arrowheads, spaced at 300-million-year intervals, point to what, today, would be considered north. You can see how, during the past 600 million years, North America has rotated about 90 degrees counterclockwise and moved all the way from the southern hemisphere to its current location in the northern hemisphere.

So how do scientists know that the continents have wandered over the earth? The answer lies in the fact that some rocks possess what is referred to as “remnant magnetism.” When crystalline rocks form, the magnetic minerals they contain are “frozen” according to the surrounding field at the time they were created. By carefully measuring the orientation of the remnant magnetism, it is possible to determine the latitude where the magnetic rocks were formed.

I figure that by the time North America and Eurasia drift another half a foot further apart, Donovan and Delaney will want to hear this story. Until then, you’ll have to do. Thanks for listening! 

January 2008

Everybody Needs a Rock

Follow the journey of a pet rock, ‘born’ approximately 1.8 billion years ago.

Author’s notes:

(1) Geologic time is translated into a 24-hour day. The beginning of the earth (4.54 billion years ago) is 00(hrs):00(min):00(sec). The present is 24:00:00. Each second equals about 52,546 years; each minute about 3.2 million years; each hour about 189 million years.

(2) The following scientific abbreviations are used: Ga (billion years ago), Ma (million years ago), Ka (thousand years ago).

My 3-year-old granddaughter, Delaney, loves books. During our last visit we read Everybody Needs a Rock, by Byrd Baylor. The book begins, “I’m sorry for kids who don’t have a rock for a friend.” Well, don’t feel sorry for us. Delaney and I have a friend named Rocky that came from a quarry in Morrison, Colo.

Rocky was born 1.8 Ga (14:29:04) in a sea located between an ancient supercontinent named Laurentia and a collection of volcanic islands (see illustration). Lava and ash from the volcanoes, and sediments from Laurentia, piled up in the sea and, throughout time, were consolidated into rocks. Propelled by plate tectonics, Laurentia swept up the sedimentary rocks and volcanic islands. The rocks were heated and squeezed into gray metamorphic rocks, pushed up to form mountains, and intruded with molten magma that ultimately cooled as pink veins in the rocks. Geologists refer to these very old crystalline rocks as “basement,” and by 1.1 Ga (18:11:06), Rocky’s home in the Colorado basement was finished. Officially, Rocky is referred to as a gneiss (pronounced ‘nice’).

The star indicates Rocky's birthplace in southwestern United States, 1.8 billion years ago.  Outlines of states are shown by red dashed lines.

Twice during Rocky’s lifetime, once between about 510 to 300 Ma (21:18:14 to 22:24:51), and more recently at 100 Ma (23:28:17), seas washed over Colorado, leaving behind vast areas of sandstone, limestone, and other sedimentary rocks. Some of these rocks subsequently were eroded away; others remain to tell their stories.

Continental plates on the earth’s surface have been drifting together and splitting up since before Rocky was born. Around 300 Ma (22:24:51), a number of plates collided to form a supercontinent named Pangea, and in doing so, pushed up the Ancestral Rocky Mountains. During the next 80 million years (25 min 22 sec), the Ancestral Rockies eroded and shed thousands of feet of sediment on the surrounding basement.

Pangea began to break apart around 180 Ma (23:02:55). From 72 to 40 Ma (23:37:10 to 23:47:19), the Rocky Mountains were thrust into the air, this time from tectonic activity on the western margin of the North American plate. But Mother Nature was not finished. Around 37 Ma (23:48:16), a massive volcanic eruption deposited ash 400 feet thick in the area just south of Rocky’s basement apartment. And to polish things off, glaciers began the final sculpting of the landscape around 1.8 Ma (23:59:26). When the Ice Age ended around 10 Ka (23:59:59.81), Rocky’s home looked much like it does today.

The next few columns will take a closer look at Rocky’s journey through geologic time. We will see how the North American plate wandered around the surface of the Earth; how those movements affected the climate; how climate changes affected life; and more. Hang on! Those articles might just stir the science in your soul! 

December 2007

Got Minerals?

Learn more about industrial mineral applications through numerous books, Web sites, and educational seminars.

During the past year, this column has also been about industrial minerals. The articles barely scratched the surface of the thousands of applications for the dozens of industrial minerals. If you like what you read, and want to learn more, here are some ideas.

The Society for Mining, Metallurgy, and Exploration (SME) recently released the 7th edition of Industrial Minerals & Rocks. It is a 1,548-page reference document covering more than 60 industrial minerals, rocks, and materials, including crushed stone and sand and gravel. If you want to know about the geology, mining and production methods, and uses of industrial minerals, it’s in the book. If you are a history buff, you can choose an industrial mineral and read about it in each of the seven editions to see how the industry has evolved throughout time. Better yet, the book contains chapters on aggregates, lightweight aggregates, crushed stone, and sand and gravel. Interested yet? If so, go to www.smenet.org.

If you are looking for a little lighter reading, try the Industrial Minerals Handybook, by Peter Harben. It’s jam-packed with resource descriptions, mining methods, specifications, production statistics, and other market-related issues. The handybook is available from many online bookstores or at www.peterharben.com.

And of course, the U.S. Geological Survey Minerals Yearbooks and Mineral Commodity Summaries (http://minerals. usgs.gov/minerals/pubs/commodity/) are world-famous collections of information on mineral commodities. The yearbooks are multi-page articles describing significant events in the minerals industries throughout the past year, and include numerous tables describing production volumes and values by state and product, as well as imports, exports, and so forth. The commodity summaries are a two-page roll-up of the industries. If you aren’t using these documents, you are missing out on a great resource.

If you want to get the industry take on industrial minerals, try visiting the Web site of the Industrial Minerals Association-North America (www.ima-na.org) or Industrial Minerals Association-Europe (www.ima-eu.org). These are especially informative sites to visit, especially if you are interested in sustainability.

And for educational information, the Mineral Information Institute (www.mii.org) has a Web page (look under homework help) that includes pictures and descriptions of the uses of many minerals, including the industrial minerals.

If you would like to get actively involved in the process, there are a number of annual meetings you can attend. At the SME annual meeting, the Industrial Minerals Division usually has a program of five sessions — each session with four to six papers. For those of you who don’t want to stray too far from aggregates, the Construction Materials and Aggregates Committee (CMAC) of SME organizes a five-session program. There are exhibits galore, as well as field trips and short courses. Come to the meeting at Salt Lake City (Feb. 24-27, 2008) — you won’t be bored! You can register on line at www.smenet.org.

Another annual meeting, the Forum on the Geology of Industrial Minerals, is dedicated entirely to industrial minerals. This is a much smaller, more personal meeting. The 44th Forum will be in Oklahoma during the spring of 2008. To learn more, use your Web search engine; and type in key words “forum geology industrial minerals.” You can expect a superb program on a variety of industrial minerals, including aggregates. And if you like to bring someone along, they have outstanding guest tours! I hope to see you at one of these meetings.

November 2007

Food for Thought

The consumption of soil is common among many birds and animals, including some of the two-legged variety.

My wife, Pam, and I discovered a fantastic new television series — Planet Earth. During one episode, a forest elephant plunged its trunk into the bottom of a lake, came up with a hunk of clay, popped it into its mouth, and ate it. Pam looked at me in amazement and blurted, “Wow! Even animals use industrial minerals!” 

Now, I had no intention of writing about eating dirt, but after Pam’s remark…

Geophagia — the consumption of soil — is a common behavior of many birds and animals. The dirt-eaters typically are herbivores, including antelopes, buffalo, chimpanzees, giraffes, gorillas, and zebras in Africa; peccaries and tapir in South America; deer in Europe and Asia; parrots in South America; and virtually all species of wild North American ungulates (hoofed animals), including bison, moose, and deer.

Humans have been eating soil since the beginning of man-kind. The clay recovered from a site occupied by early homo sapiens has mineralogical and nutritional characteristics like clays consumed by humans in Africa today. Hippocrates (circa 460 to 377 B.C.) wrote that pregnant women ate earth. Pliny the Elder (23 to 79 A.D.) wrote about a porridge-like cereal containing clay that had a soothing effect when used as a drug. And in Africa and the southern United States, some pregnant or nursing women still eat clay (known as pica).

Why do humans and other animals eat dirt? And how do dirt-eaters choose which soil to consume? The answer is somewhat elusive and is the subject of serious debate in the scientific literature. Six theories commonly are discussed among zoologists, anthropologists, and doctors. The first three theories involve an animal’s ability to self-medicate, which remains controversial because the evidence is mostly circumstantial or anecdotal.

1. Mineral supplement: Researchers have observed that animals, when presented with piles of soil, each pile containing different minerals, could recognize and choose the pile of soil with the mineral needed by their bodies.

2. Stomach acid buffer: When some hoofed animals eat a diet low in fiber, their rumens become so acidic that they kill helpful bacteria essential for digestion. Some of those animals buffer or neutralize the acid by eating highly alkaline soils similar to over-the-counter antacids.

3. Diarrhea: Bacteria and parasites release toxins that cause diarrhea. Researchers studying wild chimpanzees noticed that some of the animals suffering from severe diarrhea were eating soils rich in clays that bind the toxins. The clays are similar to those used in over-the-counter diarrhea medicines.

4. Grit: Many birds eat grit (small particles of stone) to aid digestion because birds don’t have teeth to chew their food. The grit stays in the gizzard, a muscular pouch just above the intestine that grinds the seeds that the bird has eaten.

5. Toxins: Wild fruits and nuts usually are bitter, astringent, sour, or poisonous. The seeds wild parrots eat are mostly inedible by other birds, but parrots can eat them because they also eat soils containing clay minerals that bind plant toxins.

6. Hunger: Some humans consume soil to assuage hunger. For example, the Ottomac Indians of South America made soil balls and ate more than one pound per day during the flood season, when finding food was difficult.

While some animals may instinctively eat dirt, humans have the ability to learn through experience. The bitter, toxic wild potatoes eaten by some South American Indians contain an alkaloid that causes stomach pains and vomiting. However, they have learned to make the potatoes edible by consuming them with clay that adsorbs the alkaloids.

Food for thought!