Thursday, July 19, 2012
Top 10 Signs You Might be a Geologist
10. You've responded "yes" to the question, "What have you got in there, rocks?"
9. You've taken a 15-passenger van over "roads" that were really intended only for cattle.
8. You've found yourself trying to explain to airport security that a rock hammer isn't really a weapon.
7. Your rock garden is located inside your house.
6. You've hung a picture using a Brunton as a level.
5. Your collection of beer cans and/or bottles rivals the size of your rock collection.
4. You consider a "recent event" to be anything that has happened in the last hundred thousand years.
3. Your photos include people only for scale and you have more pictures of your rock hammer and lens cap than of your family.
2. You've been on a field trip that included scheduled stops at a gravel pit and/or a liquor store.
1. You have uttered the phrase "Have you tried licking it?" with no sexual connotation involved.
Wednesday, June 13, 2012
Ramsay Fold Classifications
John Ramsay's Fold Classification
John Ramsay proposed a classification scheme for folds that is used to describe folds in profile based upon curvature of the inner and outer lines of a fold, and the behavior of dip isogons.
dip isogon: a line that connects points of equal inclination or dip on the outer and inner bounding surfaces of a folded layer
Class 1 - Dip isogons converge downward towards axial surface, signifying that the curvature of the outer arc is less than that of the inner arc
Class 1A - Limbs thicker than hinges
Class 1B - Layer thickness constant; parallel fold
Class 1C - Limbs thinner than hinges
Class 2 - Dip isogons are parallel, signifying that the curvature of the outer arc exactly matches the curvature of the inner arc; similar fold
Class 3 - Dip isogons diverge downward towards axial surface, signifying that the curvature of the outer arc is greater than that of the inner arc
Class 1B (parallel) and Class 2 (similar) folds are the most common folds seen in the field. Concentric folds are a special case of Class 1B (parallel) folds where the outer and inner bounding surfaces define arcs with a common center of curvature. These types of folds are common in upper crustal tectonic settings, where most deformation occurs by processes that only permit limited ductile flow of rock. Most of the deformation is accommodated by slip on bedding or layer boundaries (flexural slip folding). Class 2 (similar) folds have relative thinning of the limbs and thicking of the hinges. These types of folds are common in metamorphic terranes, where most deformation occurs by processes that permit extensive ductile flow of rock.
Sources:
Folding and Fracturing of Rocks, John G. Ramsay, 1967
Structural Geology of Rocks, 2nd Edition, George H. Davis & Stephen J. Reynolds, 1996
http://ocw.mit.edu/courses/earth-atmospheric-and-planetary-sciences/12-113-structural-geology-fall-2005/lecture-notes/part6_dctl_fldfb.pdf
John Ramsay proposed a classification scheme for folds that is used to describe folds in profile based upon curvature of the inner and outer lines of a fold, and the behavior of dip isogons.
dip isogon: a line that connects points of equal inclination or dip on the outer and inner bounding surfaces of a folded layer
Class 1 - Dip isogons converge downward towards axial surface, signifying that the curvature of the outer arc is less than that of the inner arc
Class 1A - Limbs thicker than hinges
Class 1B - Layer thickness constant; parallel fold
Class 1C - Limbs thinner than hinges
Class 2 - Dip isogons are parallel, signifying that the curvature of the outer arc exactly matches the curvature of the inner arc; similar fold
Class 3 - Dip isogons diverge downward towards axial surface, signifying that the curvature of the outer arc is greater than that of the inner arc
Class 1B (parallel) and Class 2 (similar) folds are the most common folds seen in the field. Concentric folds are a special case of Class 1B (parallel) folds where the outer and inner bounding surfaces define arcs with a common center of curvature. These types of folds are common in upper crustal tectonic settings, where most deformation occurs by processes that only permit limited ductile flow of rock. Most of the deformation is accommodated by slip on bedding or layer boundaries (flexural slip folding). Class 2 (similar) folds have relative thinning of the limbs and thicking of the hinges. These types of folds are common in metamorphic terranes, where most deformation occurs by processes that permit extensive ductile flow of rock.
Sources:
Folding and Fracturing of Rocks, John G. Ramsay, 1967
Structural Geology of Rocks, 2nd Edition, George H. Davis & Stephen J. Reynolds, 1996
http://ocw.mit.edu/courses/earth-atmospheric-and-planetary-sciences/12-113-structural-geology-fall-2005/lecture-notes/part6_dctl_fldfb.pdf
Wednesday, May 23, 2012
Near passerine? How can you be near passerine?
Near passerine? How can you be near passerine? Doesn't that just make you non-passerine?
I know very little about bird lineages, and I recently read an article about the replacement of non-passerine birds in Europe with passerine birds. I was trying to determine what passerine versus non-passerine birds were, generally, but when I looked up woodpeckers I found that they, and several other lineages, were known also as "near passerines." My search led me to citations that stated that near passerines are a group that are believed to be related to true passerines due primarily to ecological similarities. It is thus far undetermined whether or not all near passerines are related to true passerines, but new molecular data apparently makes it appear unlikely. So, that is, briefly, a near passerine.
I know very little about bird lineages, and I recently read an article about the replacement of non-passerine birds in Europe with passerine birds. I was trying to determine what passerine versus non-passerine birds were, generally, but when I looked up woodpeckers I found that they, and several other lineages, were known also as "near passerines." My search led me to citations that stated that near passerines are a group that are believed to be related to true passerines due primarily to ecological similarities. It is thus far undetermined whether or not all near passerines are related to true passerines, but new molecular data apparently makes it appear unlikely. So, that is, briefly, a near passerine.
Wednesday, March 16, 2011
Subduction zones and earthquakes
I am still waiting to hear from a couple friends in Japan, and I hope to hear that they and their families are safe. There are also extensive fears about nuclear radiation, as well as problems with evacuations and shelter for those displaced, throughout the Tohoku region. There are many good resources for information on these factors, so I will not focus on them.
Instead I will focus on the geological effects of this earthquake, since I understand these a bit better.
The 8.9 magnitude earthquake has shifted the Earth of its access by about 16.5 cm. This will cause the planet to rotate faster and shorten the length of the Earth's day by 1.8 millionths of a second or so. It has also moved the coastline of Japan in the Tohoku region by about 4 m to the east in some regions.
The cause of this earthquake is due to the subduction zone which lies to the east of Japan (the thick line to the east of the epicenter on the image below). The Pacific Plate is being subducted, or pulled under, the North American Plate, on which Japan lies. The motion of the scraping of the two plates together builds up strain energy which then must be released at some indeterminable period. The release of the strain results in an earthquake, in this case a very large earthquake.
When the movement of the Earth occurred underwater, it displaced a large bit sea water and thus created the large tsunami which hit the coastal regions of the Tohoku region. The Pacific Plate's maximum westward movement was about 20 m, with the movement along the fault reducing as you go away from the epicenter. This is also why the amount of shaking and damage decreased away from the epicenter and fault.
BBC - How the quake has moved Japan
Instead I will focus on the geological effects of this earthquake, since I understand these a bit better.
The 8.9 magnitude earthquake has shifted the Earth of its access by about 16.5 cm. This will cause the planet to rotate faster and shorten the length of the Earth's day by 1.8 millionths of a second or so. It has also moved the coastline of Japan in the Tohoku region by about 4 m to the east in some regions.
The cause of this earthquake is due to the subduction zone which lies to the east of Japan (the thick line to the east of the epicenter on the image below). The Pacific Plate is being subducted, or pulled under, the North American Plate, on which Japan lies. The motion of the scraping of the two plates together builds up strain energy which then must be released at some indeterminable period. The release of the strain results in an earthquake, in this case a very large earthquake.
When the movement of the Earth occurred underwater, it displaced a large bit sea water and thus created the large tsunami which hit the coastal regions of the Tohoku region. The Pacific Plate's maximum westward movement was about 20 m, with the movement along the fault reducing as you go away from the epicenter. This is also why the amount of shaking and damage decreased away from the epicenter and fault.
BBC - How the quake has moved Japan
Friday, March 11, 2011
8.9 Magnitude Earthquake Offshore Japan
An 8.9 magnitude earthquake occurred offshore of Honshu, Japan, on Friday, March 11, 2011, at 14:26 local time. This is the largest earthquake the country has ever experienced, and the seventh largest ever recorded. It occurred 382 km northeast of Tokyo.
The towns along a 2,100-km range of eastern coastline of Honshu were affected by the earthquake and its 19 aftershocks, most of which were greater than 6.0 magnitude. A 7-metre tsunami was launched which carried cars, boats, and even planes inland. At least 60 people have been killed.
Tsunami warnings have been issued for the west coast of South America, the west coast of the U.S., Hawaii, New Zealand, and other areas in the Pacific: Pacific Tsunami Warning Center.
More News:
Earthquake: Japan Hit by 8.9 Earthquake/Japan Tsunami Warning (Sydney Morning Herald)
The towns along a 2,100-km range of eastern coastline of Honshu were affected by the earthquake and its 19 aftershocks, most of which were greater than 6.0 magnitude. A 7-metre tsunami was launched which carried cars, boats, and even planes inland. At least 60 people have been killed.
Tsunami warnings have been issued for the west coast of South America, the west coast of the U.S., Hawaii, New Zealand, and other areas in the Pacific: Pacific Tsunami Warning Center.
More News:
Earthquake: Japan Hit by 8.9 Earthquake/Japan Tsunami Warning (Sydney Morning Herald)
Friday, November 19, 2010
Mediterranean Sharks Resulted from Wrong Turn
A new study involving Mediterranean great white sharks suggests that they are more closely related to sharks from Australia and New Zealand, and less similar to those of the Atlantic Ocean as previously thought. It is believed that the group of Mediterranean sharks arrived about 450,000 years ago after making a "wrong turn" on their return to the location of their birth. This period of time was an interglacial period, in which extreme current variations were occurring. The change in warm and cold currents may have been significant enough to alter the course of the migrating sharks. If only a few shark pups were born in the Mediterranean waters, the study indicates that this would be all that was needed to begin a new cycle of migration to the same location for future generations. This is an interesting study which may have implications for other species migrations during interglacial periods.
Thursday, October 21, 2010
Quetzalcoatlus
Quetzalcoatlus was a Late Cretaceous pterosaur known from North America, and a member of the family Azhdarchidae - known as advanced, toothless pterosaurs characterised by long, stiffened necks. Its name comes from Quetzalcoatl, a feathered serpent deity of the peoples of central Mexico, Nicaragua, and Honduras.
Please visit Shiraishi Mineo's Jurassic Gallery, the talented artist who created this image, with a beautiful gallery of images of dinosaurs, pterosaurs, and other prehistoric animals. This was my favourite image of all the Quetzalcoatlus images I have seen so far.
The feeding style adopted by Quetzalcoatlus is controversial. Originally it was theorised that Quetzalcoatlus fed on fish, scooping them from the sea as it flew overhead. It has also been suggested that the pterosaur was a scavenger, because some remains had been found in an area devoid of lakes or rivers, and was far inland. But the shape of its jaw suggested to others that it could have fed by skimming over the sea and collecting fish in its mouth. This skimming technique was later disproved because the energy costs for the shape of the pterosaur would be too high, as well as the fact that the remains were found in an inland area rather than a coastal environment. Another theory suggests that Quetzalcoatlus hunted by terrestrial stalking, hunting small vertebrates on land or in streams. The modern analogue for this behaviour is in storks. Quetzalcoatlus would have walked on its hind legs and folded wings.
One important point to remember is that pterosaurs were not dinosaurs! Dinosaurs are terrestrial animals only! This includes plesiosaurs and similar marine creatures contemporaneous with dinosaurs, which were actually marine reptiles.
The feeding style adopted by Quetzalcoatlus is controversial. Originally it was theorised that Quetzalcoatlus fed on fish, scooping them from the sea as it flew overhead. It has also been suggested that the pterosaur was a scavenger, because some remains had been found in an area devoid of lakes or rivers, and was far inland. But the shape of its jaw suggested to others that it could have fed by skimming over the sea and collecting fish in its mouth. This skimming technique was later disproved because the energy costs for the shape of the pterosaur would be too high, as well as the fact that the remains were found in an inland area rather than a coastal environment. Another theory suggests that Quetzalcoatlus hunted by terrestrial stalking, hunting small vertebrates on land or in streams. The modern analogue for this behaviour is in storks. Quetzalcoatlus would have walked on its hind legs and folded wings.
One important point to remember is that pterosaurs were not dinosaurs! Dinosaurs are terrestrial animals only! This includes plesiosaurs and similar marine creatures contemporaneous with dinosaurs, which were actually marine reptiles.
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