Stories tagged geology

Literally dig deeper into the earth surface and discover what is lying right under your feet.

Sep
16
2013

Fossil of Hallucigenia in Burgess Shale
Fossil of Hallucigenia in Burgess ShaleCourtesy ap2il via Flickr
One of the strangest creatures to emerge from the famed Burgess Shale in the mountains of British Columbia, is the rightly named Hallucigenia, a strange spiky, wormlike creature that once scuttled across the Cambrian sea bottom more than 500 million years ago. Originally considered a totally unique (and baffling) creature, Hallucigenia has now been linked to other similar-aged wormlike creatures found around the world.

Hallucigenia first came to light in 1909 after Charles Doolitle Walcott, an expert in trilobites and secretary of the Smithsonian Institute, discovered a Lagerstätte in the mountains of British Columbia that was unlike any other found before.

Location of Walcott Quarry as seen from Field, BC
Location of Walcott Quarry as seen from Field, BCCourtesy Mark Ryan
Located in Yoho National Park on a steep slope between Mount Field and Wapta peak above the railroad town of Field, B.C., Walcott's quarry produced some of the strangest creatures - many of them soft-bodied and rarely found in the fossil record. The rock section, previously known as the Stephens Formation became known as the Burgess Shale, after nearby Burgess Pass. In the years following the discovery, Walcott and other scientists studied the strange fossils in an effort to decipher them and the environment in which they had lived and died.

Because of the high degree of preservation, the creatures that made the fossils were most likely buried suddenly in some sort of giant underwater mudslide that quickly entombed an entire marine community in an anoxic environment where decomposition was stifled. A perfect environment for preserving the soft-bodied tissue.

Display model of Hallucigenia: Royal Tyrrell Museum in Drumheller, Alberta
Display model of Hallucigenia: Royal Tyrrell Museum in Drumheller, AlbertaCourtesy Mark Ryan
Some of the Burgess Shale denizens appeared to be of completely new and unknown phyla with bizarre and unfamiliar body plans and no known descendents in the modern age. Hallucigenia certainly led the pack in this department. The tiny strangely constructed worm was only about an inch in length and confounded Walcott and other scientists for more than a century. They couldn''t even say for sure which side was up or down. Early Hallucigenia fossils showed a row of seven tentacles along one side. The opposite side contained seven sets of stiff spikes that were interpreted to be legs. A truly bizarre, aptly named freak-show creature that would be right at home in your average nightmare.

New evidence can often turn an old idea on its ear - or in this case, on its back. Recent scrutiny of newer, better-defined Hallucigenia fossils has revealed another set of "tentacles", leading scientist to realize they had Hallucigenia all flipped around. What they once thought was its top side was actually its bottom. Its dorsal "tentacles" were actually its legs. And its spiky "legs" belonged on its back, probably to serve as protection against predators.

This information along with a new study published in Proceedings of the Royal Society B now places Hallucigenia within a group of other worm-like creatures whose fossils are found around the world, including China, Canada, Great Britain, and Australia. It also links it to a living group - Onychophora - the velvet worms that mostly inhabit the tropical forests of the Southern Hemisphere.

"They may not be exactly the same species, but they are all probably related to the same group of worm-like creature that we call lobopods," said Dr. Jean-Bernard Caron, curator of invertebrate paleontology at the Royal Ontario Museum and the study's lead researcher. Caron is an expert in Burgess Shale fossils and his study of Hallucigenia and other fossils from the formation continues to glean new knowledge about the strange creatures that existed in the so-called Cambrian Explosion. Check out Caron's Burgess Shale website. It's full of great information about the quarry and the incredible fossils found there.

Burgess Shale location: Walcott Quarry sets on steep slope in valley between Mt. Wapta and Mt. Field.
Burgess Shale location: Walcott Quarry sets on steep slope in valley between Mt. Wapta and Mt. Field.Courtesy Mark Ryan
Walcott's Burgess Shale quarry has been designated a World Heritage site. The only way to visit it (or the fossil fields on nearby Mt. Stephen) is through guided hikes led by either Parks Canada or The Burgess Shale Geoscience Foundation. The 10 hour round-trip hike (rated moderate to difficult) takes participants up 2500 feet in elevation to Mt. Fields and requires reservations and a deposit. Fossil collecting is prohibited but the views are said to be spectacular.
­
SOURCE and LINKS
The Province story
The Burgess Shale at Smithsonian website
Dr. Caron's Burgess Shale website
Parks Canada Burgess Shale info

Microbes: Some have been found surviving deep beneath the ocean floor.
Microbes: Some have been found surviving deep beneath the ocean floor.Courtesy EMSL
Microbes found living in rocks 1.5 miles under the ocean floor live such slow-paced lives that they reproduce only every 10,000 years or so. That's a long time between generations. They live this way in rocks estimated to be 100 million years old. The discovery was announced by scientists from the Integrated Ocean Drilling Program at a meeting of geochemists at the Goldschmidt onference in Florence, Italy. Scientists have also discovered other life forms - viruses and fungi - living zombie-like existences in the same deep rock layers.

Dr Beth Orcutt of Bigelow Laboratory for Ocean Sciences in Maine wonders how life exists in such extreme environments and where Earth's biosphere actually terminates.
"The deeper we look, the deeper we are still finding cells," she said, "and the discussion now is where is the limit? Is it going to be depth, is it going to be temperature? Where is the limit from there being life to there being no life?"
The density of the microbial population living in the deep rocks is miniscule compared to those found at the surface, but scientists still wonder if the microbes can actually be changing the lithosphere through chemical reaction with carbon and other elements in the rocks, and what results from that interaction.

SOURCE and LINKS
BBC Science-Environment news
Integrated Ocean Drilling Program page
Goldschmidt conference page
Bigelow Laboratory for Ocean Sciences page

For a long time, scientists have known a major volcano complex was under the Pacific Ocean off the coast of Japan. But upon further inspection, they've discovered it's one huge volcano, measuring 280 miles by 400 miles across. You can read more about this huge discovery right here.

Jul
24
2013

Green River Formation slab: The head end of Lepisosteus has been partially prepared.The rest of the fossil is hidden beneath a layer of rock matrix.
Green River Formation slab: The head end of Lepisosteus has been partially prepared.The rest of the fossil is hidden beneath a layer of rock matrix.Courtesy Mark Ryan
I've had the great fortune of being able to volunteer in the paleontology lab at the Science Museum of Minnesota. I'm in my fourth month there and it's been a real blast. My first project was preparing (cleaning) the skull of a small oreodont collected from the White River Formation in Wyoming. This is the same formation exposed in the fossil-rich South Dakota Badlands. By cleaning, I mean removing all the rock (matrix) in which the skull is encased. I've also helped patch up the casts of a couple of lambeosaurus skulls, and spent a few days puzzling over a crocodile skull reduced to about 1000 pieces.

Removing matrix: Science Museum of Minnesota fossil preparator Becky Huset uses an air scribe to methodically remove the thin rock veneer covering the remains of Lepisosteus, a fossil gar.
Removing matrix: Science Museum of Minnesota fossil preparator Becky Huset uses an air scribe to methodically remove the thin rock veneer covering the remains of Lepisosteus, a fossil gar.Courtesy Mark Ryan
At the moment, preparators been working on the remains of a 52 million year-old gar collected from the Green River Formation in southwestern Wyoming. Most of the work is being done by the more experienced volunteers in the lab but I've been able to help a little, taking my turn with the air scribe to reveal some caudal scales in their rocky grave. This particular specimen, an ancient member of Lepisosteus, was collected in Lincoln County, Wyoming. It's fascinating work uncovering something that last saw sunlight more than 50 million years ago. Now, at least, its remains can bask in the glare of the paleo lab's artificial lights.

Lepisosteus tail comes to light: SMM paleo lab technician, Kay Blair, works at revealing the 52 million year-old gar's tail rays and posterior scales.
Lepisosteus tail comes to light: SMM paleo lab technician, Kay Blair, works at revealing the 52 million year-old gar's tail rays and posterior scales.Courtesy Mark Ryan
Fifty some million years ago, the gar lived in a large body of water known as Fossil Lake, one of three intermountain lakes that existed at different times in a sub-tropical environment in that part of Wyoming. The intermountain basin in and around the lake teemed with both floral and faunal life that over about 4000 years lived and died and were fossilized forming one of the great Lagerstätten in the world. The surrounding mountains were composed mainly of limestone, and the rivers and streams eroding those mountains carried high levels of calcite (CaC3) into the lake, resulting in a high sedimentation rate that added to the ideal fossilization environment.

(More about the Green River lakes and fossils in previous Buzz story).

Most of the fossils coming out of the Fossil Lake strata have been fossilized by a process called permineralization, where mineral-rich water permeates all the spaces and pores in the skeleton and the minerals (in this case calcite) crystallize out of the water replacing bone material down to the cellular level. Some carbonization is also involved. This process depletes the remains of volatiles and is caused by the heat and pressure of sediment compression, which also crushes and flattens the fossils, and tends to color them either brown or black.

Scattered bones: The fossil gar's head was blown apart by gases that built up during its decomposition.
Scattered bones: The fossil gar's head was blown apart by gases that built up during its decomposition.Courtesy Mark Ryan
That's very apparent with our gar. Although only portions of the fish's remains have been exhumed (its head and tail) the fossil is already providing some information about what followed the gar's death (taphonomy). Lepisosteus favored the shallow, swampy edges of Fossil Lake and when it died it probably floated on the surface for a while giving bacteria time to enter its mouth and gills and begin their decomposition work before the corpse was buried beneath sediments.

We can deduce this scenario by the manner the remains are preserved. The bones of the gar's skull and jaws are scattered and jumbled in a mish-mash of bones and scales. The head appears to have been blown apart, and that's probably what happened. As the microbes feasted on the fish's head, they released gases inside the corpse which built up, and bloated the gar to a point where it burst from the internal pressure. The mandibles, the cranium, and other bones broke apart before settling to the bottom and are disarticulated. The very end of the tail, however, shows no such disruption. The rays of the caudal fins looking almost as fresh as they did when the gar died half a million centuries ago.

Scales as tough as nails: In life, an enamel-like tissue called ganoin made the diamond-shaped scales of Lepisosteus tough and predator-resistant.
Scales as tough as nails: In life, an enamel-like tissue called ganoin made the diamond-shaped scales of Lepisosteus tough and predator-resistant.Courtesy Mark Ryan
The scales of its mid-section are beginning to come to light. These diamond-shaped structures were covered with ganoin, an enamel-like tissue containing less than five percent organic material. The mineralized tissue gave Lepisosteus a very tough, predator-resistant exterior when it was alive but not so resistant to the bacteria that attacked the gar from the inside after it died. Preliminary work of the mid-section is showing signs of decomposition there but further work required.

One of the major experts on the fossils found in the Green River Formation is Lance Grande, a graduate of the University of Minnesota (and elsewhere) who has been working at Chicago's Field Museum for the past few decades. In the early '80s, Dr. Grande wrote a hefty bulletin titled Paleontology of the Green River Formation for the Wyoming Geological Survey, and has now come out with a new book titled The Lost World of Fossil Lake: Snapshots from Deep Time. In a recent television interview, Dr. Grande talked about his book and about the fossils found in the Green River Formation.

Hundreds of thousands of finely preserved fossils from Fossil Lake deposits can be found in museum displays and on rock shop shelves world-wide. The best fossils were buried quickly and preserved in near pristine condition. Many of these come from what used to be the deep center of the lake where conditions were probably anoxic and burial fairly swift. At times during Fossil Lake's history events like seasonal algal blooms or rapid turnovers of the water column occurred and caused massive die-offs of fishes. Other fish, like our gar, probably just died a regular death.

Progress so far: After several weeks of preparation, the remains of Lepisosteus are becoming more defined.
Progress so far: After several weeks of preparation, the remains of Lepisosteus are becoming more defined.Courtesy Mark Ryan
Every fossil tells a story, and our gar is no exception. Back in the Eocene epoch it lived for a short time in the then subtropic environment of southwest Wyoming, doing what gars do before it finally died along the shores of Fossil Lake. After it was buried, it was fossilized, dug up, and transferred to the collections vault of the Science Museum of Minnesota. A few months ago, it was retrieved from the vault and brought into the paleo lab where it's been worked on each week by several people. Whatever the gar was thinking when it was alive back in the late Eocene, you can be sure it was unaware that its post-mortem life would provide hours of detailed work, study and fascination for another curious life-form 52 million years later.

SOURCES AND LINKS

Green River Fossil Adventures
Fossil Butte National Monument
More about Green River Formation at Fossil News
The Green River Formation: A Fossil Fiesta
Green River Info at UCMP Berkeley

Brachiopod fossil in limestone matrix: Typical fossil found in the quarries at Lilydale and elsewhere in southern Minnesota.
Brachiopod fossil in limestone matrix: Typical fossil found in the quarries at Lilydale and elsewhere in southern Minnesota.Courtesy Mark Ryan
In response to last week's tragedy at the fossil quarries in Lilydale Regional Park, science writer Anne Brataas has written about the importance of continuing the practice of taking field trips outside the classroom, despite the inherent dangers real life can present.

Brataas is the CEO and founder of The Story Laboratory, LLC, as well as an instructional designer and science historian.

SOURCE
MinnPost article

John Wesley Powell: The Ute Indians called him Kapurats, meaning "arm off".
John Wesley Powell: The Ute Indians called him Kapurats, meaning "arm off".Courtesy Public domain via the National Park Service
A remarkable figure in the history of American science, John Wesley Powell was born this day in 1834 in Mount Morris, New York.

During the late 1860s and early 1870s, and despite losing his right arm during the Civil War, Powell led several extensive expeditions into the rugged, unexplored regions of the American West collecting geological, geographical, and ethnological data, along with natural history specimens for the United States government. A fervent scientist, Powell served as director of both the U.S. Geological Society and the Bureau of Ethnology, and helped found the National Geographic Society.

Powell is probably best remembered for his study and befriending of the Ute people, and for making the first explorations of the Colorado River (then called the Grand River) and the Grand Canyon. Lake Powell, a large reservoir located on the border of northern Arizona and southern Utah is named in his honor.

LINKS
NPS-USG Powell Info page
Powell Chronology
J.W. Powell Wikipedia page
More about Powell
Powell Expedition photos

Mar
15
2013

Acasta Gneiss: at approximately 4.03 billion years-old, the tonalite gneiss is the oldest rock exposed on the surface of the planet.
Acasta Gneiss: at approximately 4.03 billion years-old, the tonalite gneiss is the oldest rock exposed on the surface of the planet.Courtesy Mark Ryan
I recently attended a geology seminar sponsored by the Geological Society of Minnesota. The event took place at Macalester College in St. Paul, and was led by Jeff Thole, laboratory supervisor and instructor in the college's Geology Department. Jeff is extremely knowledgeable and enthusiastic about geology, and in the course of cramming a semester's worth of geology into the two hour lab, he mentioned that he had in his office one of the oldest rocks in the world: a nice chunk of Acasta gneiss. After finishing his talk about the rock cycle, and as everyone began examining the variety of rock types spread out on lab tables in several rooms, Jeff brought out the chunk of ancient gneiss for everyone to see.

Found on an island in the extreme and very isolated northern regions of Canada's Northwest Territories, the Acasta gneiss has been radiometrically dated to be upwards to 4.03 billion years old! That's a number that's not very easy to comprehend. The Earth itself is estimated to be just a half-billion years older, so the Acasta gneiss (pronounced nice) is some of the very earliest crustal rock still existing on Earth's ever-changing surface. For a rock unit to withstand 4 billion years of the rock cycle - where the forces of erosion and plate tectonics are constantly at work wearing down, reworking and remelting rocks - that's quite a feat if you think about it.

To give you a better idea of the vast amount of time we're talking about here, let's first reduce it to a more comprehendible time-frame. If you were able to take a single photograph of the Earth each year for those 4 billion years (4,000,000,000 photos) and then made a time-lapse video of all those photos (at 30 frames/photos per second), and started watching the video today, it would take you more than 4 years of constant, around-the-clock viewing to watch it from start to finish. You'd still be watching it in 2017, when non-avian dinosaurs suddenly go extinct about three-and-a-half weeks before the end of the video. We modern humans wouldn't appear for the first time until sometime in the show's last couple hours.

Acasta gneiss outcrop location: The exposure is about 180 miles north of the town of Yellowknife in Canada's Northwest Territories.
Acasta gneiss outcrop location: The exposure is about 180 miles north of the town of Yellowknife in Canada's Northwest Territories.Courtesy D-Maps.com
But back to the rock itself. The ancient gneiss is named after the Acasta River, located east of Great Bear Lake, where the outcrop was first found in the 1980s. The exposure is about 300 kilometers (180 miles) from Yellowknife, so the only practical way to get there is by float plane.

Composed mostly of the minerals quartz and feldspar, the Acasta gneiss was formed during the Hadean, the earliest eon in Earth's history. Its composition leads geologists to surmise that it was probably formed from highly metamorphosed granite subjected to unimaginable heat and pressure. The exact origin of that granite is unknown, but its presence indicates continental crust (and surface water) were probably already present in those very ancient times.

AGE BEFORE BEAUTY

Morton Gneiss: Minnesota's younger but prettier "Rainbow Granite" (seen here in a quarry near Morton, MN) has been used to decorate buildings around the country. It's also a popular material for countertops and cemetery headstones. The banding and severe swirling evident in the rock indicates that, at some point, it went through a period or periods of high heat and enormous pressure.
Morton Gneiss: Minnesota's younger but prettier "Rainbow Granite" (seen here in a quarry near Morton, MN) has been used to decorate buildings around the country. It's also a popular material for countertops and cemetery headstones. The banding and severe swirling evident in the rock indicates that, at some point, it went through a period or periods of high heat and enormous pressure.Courtesy Mark Ryan
It may interest you to know that Minnesota has its own ancient gneisses exposed in outcrops in the Minnesota River Valley. The most well-known is the gneiss that's quarried around the town of Morton, Minnesota. At nearly 3.6 billion years old, Morton gneiss is not quite as ancient as the Acasta rock but what it lacks in age it makes up for in beauty. Known in the construction trade as Rainbow Granite, polished panels of the banded and severely swirled Archean-aged-aged migmatitic gneiss can be found decorating building facades throughout the country.

TECTONIC VS MARKET FORCES

An enterprising miner from Yellowknife has filed a claim on the Acasta gneiss site, and has been trying to market the ancient rock. This doesn't set well with many in the geological community, who think the rare outcrop should be preserved for scientific study. They also say the prospector could be misrepresenting the public since not all the rock in the exposure dates back to 4 billion years, and it's very expensive to validate the age of any one piece.

THE DATING GAME

So how exactly has the Acasta gneiss been dated so precisely? Zircon crystals found in the rock's mineral structure trap uranium in their lattices when they form and can act as timekeepers through measuring the decay of the uranium into lead. The half-life of uranium is a known number (4.47 billion years for U-238; 704 million years for U-235), so measuring the ratio between number of parent atoms (uranium) to the number of daughter atoms (lead) allows for a very precise estimation of age. But even zircon crystals aren't immune from 4 billion years of exposure to the elements. Things like naturally occurring radiation can damage or alter them and thus skew the measurements. But by using an instrument called the Sensitive High-Resolution Ion Microprobe (aka SHRIMP) researchers are able to focus a beam of oxygen ions on a tiny unaffected segment of the zircon' s surface, remove atoms from it, and then analyze their isotopic composition. The SHRIMP was developed at Australian National University.

Jeff Thole's sample was given to him by a geologist from the Geological Survey of Canada, which purchased a SHRIMP and used it to date the Acasta rocks. It should be noted that an older Canadian rock unit supposedly exists in the greenstone belt east of Hudson Bay, but there's still some contention regarding this, since the method of radiometric dating isn't the same that was used to date Acasta samples.

Whether the Acasta gneiss is the remaining crust of a protocontinent that existed when the Earth was still a relatively young, hot mass of accreted material remains a mystery at this point, but scientist named the time the Hadean for good reason: back then it must have been literally Hell on Earth.

LINKS
Field trip to Acasta Gneiss outcrop
Acasta Gneiss info by Carl Zimmer
Geologists balk at prospector's plan
More Morton gneiss info

Mount Etna eruption

by mdr on Feb. 19th, 2013

Here's something to add warmth to a cold winter day. Mount Etna, the well-known stratovolcano on the island of Sicily erupted last night (February 19 Italy time) with a beautiful display of boiling hot lava fountains. Luckily, someone captured it on video so we can all enjoy it (with music, too!).

How old does this look?: New research says parts of the Grand Canyon may be 65 million years, or so, older than originally thought.
How old does this look?: New research says parts of the Grand Canyon may be 65 million years, or so, older than originally thought.Courtesy chensiyuan
Grand Canyon, could you please show us your birth certificate? A new theory that parts of the Grand Canyon were carved as far back as dinosaur days has geologists picking sides on a controversy. New research contends that the western end of the canyon might be up to 70 million years old, carved by an ancient river that flowed in the opposite direction of today's Colorado River. Conventional theories about the canyon had its aged pegged at 5 to 6 million years old.

So what do you think?

Earthquake damage
Earthquake damageCourtesy USGS/Earthquake Science Center
A court in Italy has sentenced six scientists and an ex-government official to six years in prison for failing to properly warn the public about a devastating earthquake that killed 309 residents of the town of L'Aquila in 2009. The seven defendants were convicted of manslaughter and also ordered to pay for damages and court costs.

I think the court itself has failed to predict just how idiotic this irrational prosecution looks to the world scientific community. Let's hope an appeals court will be reasonable enough to override this terrible injustice.

SOURCES
BBC story
Scientific American on "Bizarre trial".