Geo Postings

Geonews Clips – April 28, 2008

2008-04-29T14:02:00.000-07:00

The argon-argon age analysis method is used to determine the age of rocks over a wide time span. However, Paul Renne, director of the Berkeley Geochronology Center and an adjunct professor of earth and planetary science at UC Berkeley, has contended that this method had systematic errors that resulted in uncertainties of about 2.5 percent in age analyses. Recent refinements to this technique have greatly improved precision in age analyses.

The National Seismic Hazard Maps just published by the U.S. Geological Survey provides assessment of earthquake hazards estimation for the United States.

Carbon dioxide levels were well regulated for hundreds of thousands of years by the Earth's natural feedback mechanism say scientists in the journal Nature Geoscience. They also state that human activity is now the cause for elevated CO2 emissions such that the planet's natural balancing mechanism cannot keep up.

Go to www.earthmaps.com/geology_news.htm for links to these topics.

Geonews Clips – April 15, 2008

2008-04-15T11:01:00.000-07:00

Is the Grand Canyon millions of years old? New research on the Grand Canyon formation suggests that parts of the canyon were formed more than 50 million years earlier than previously thought. Most researchers pegged the canyon’s formation at about 6 million years ago. Age analyses of rocks based upon uranium-thorium-helium dating, however, indicate that rocks from both the rim and floor of the Upper Granite Gorge cooled at the same time – about 55 million years ago – supporting the premise that the gorge formed from pre-existing canyons.

An intact, frozen baby woolly mammoth found in the Russian Arctic last year underwent computer tomography scans recently. The scans revealed the first in-depth internal information of an extinct mammal.

Vanishing lake? It happened in Chile where melt water from a glacier filled a lake thereby increasing pressure on the associated ice sheet. The lake water finally emptied into a nearby river – the emptying lake water initiated a tsunami that rolled through the nearby river.

Reduction in cloud cover boosted Cretaceous warming spell? Scientists suggest that although atmospheric levels of carbon dioxide were 4 times higher than today’s levels, it was still not enough to produce the tropical temperatures that existed during the Cretaceous. The lack of cloud cover could result in increased temperatures – and if this is correct, it has implications for today’s global warming models.

Links to these news clips are posted at: www.earthmaps.com/geology_news.htm

Geonews clips – March 18, 2008:

2008-03-18T14:05:00.000-07:00

Kilauea- The ongoing eruption of Kilauea volcano has destroyed almost 200 structures and buried almost nine miles of highway. Current activity includes lava continuing to flow into the ocean at two locations. A new crater gas vent has also formed and is spewing sulfur dioxide at record rates.

Ice Age Axes – A Dutch amateur archaeologist found 28 100,000-year-old axes in gravel dredged from the North Sea. These axes were presumably used by mammoth hunters who roamed the area now covered by the North Sea.

Dino-Era Feathers – Seven perfectly preserved feathers of approximately 100 million years in age were found encased in amber in western France. Because the feathers have feather-like fibers associated with some two-legged dinosaurs and some features of modern bird feathers, they could provide data on a significant stage in feather evolution.

Fossil Primates Inhabited North America Before Europe? – Chris Beard of the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania, discovered a 55 million year-old primate fossil. The fossil came from the Gulf Coastal plain of Mississippi, and is a very primitive relative of tarsiers, which now live in southeast Asia. The age of this fossil find suggests that primates inhabited North America prior to their occurrence in Europe.

Links for these news stories are at:
http://www.earthmaps.com/geology_news.htm

Geonews clips – March 5, 2008:

2008-03-04T14:11:00.000-08:00

The “Monster” – a newly identified fossil marine reptile - was excavated last summer on Norway’s Arctic island, Spitsbergen. At about 50 feet in length, this pliosaur is one of the largest marine reptiles ever found. Pliosaurs were the top marine predators during the Jurassic period (200 to 145 million years ago).

A catastrophic flood is probably the reason for an earth-cooling event that happened about 8,000 years ago. Canadian geologists believe that a huge glacial lake that covered parts of Manitoba, Saskatchewan, Ontario, North Dakota, and Minnesota rapidly drained, sending a flow of water 15 times greater than the current discharge of the Amazon River into the Hudson Strait and Labrador Sea. By some estimates, sea level rose up to 45 feet, and Western Europe cooled by about 3 degrees Celsius for 200-400 years.

A shift in tectonic plates? Some geologists now have direct evidence of how and when tectonic plates descend into the deeper parts of the Earth. Contrary to current theory, it appears that denser plates are more likely to hold in the upper mantle while lighter plates sink faster into the lower mantle. The denser plates usually flatten when they reach the upper-lower mantle boundary; the lighter plates are more likely to fold above the boundary of the lower mantle for 10’s of millions of years. Once a critical mass is attained, they then descend quickly into the lower mantle.

A recently found fossil bat may be the key to knowing whether bats could fly before they developed their internal sonar navigation system. The fossil bat was found in the Green River Formation of Wyoming and is about 52 million years old. Because the fossil bat lacked the skull features necessary for echolocation, it now seems likely that bats could fly prior to developing their internal sonar for navigating and hunting.

Links for these news stories are at:

http://www.earthmaps.com/geology_news.htm

Carbonate Paleosol Special Paper - a good read!

2007-02-26T14:47:00.000-08:00

There is a great new Geological Society of America publication out now. It’s GSA Special Paper 416 – Paleoenvironmental Record and Applications of Calcretes and Palustrine Carbonates, edited by Ana Maria Alonso-Zarza and Lawrence H. Tanner. To be up front about this, I do have a paper in this volume. It’s entitled “Calcic pedocomplexes – regional sequence boundary indicators in Tertiary deposits of the Great Plains and western United States, p. 1-15. But, there are other – 13 in fact, equally good – papers in this volume that anyone who works in continental deposits should read. Topics range from paleosol catenas, palustrine carbonates, to age analysis of calcretes, and span time intervals from the Paleozoic to the Quaternary. The field studies are geographically diverse, including areas from South America, Anarctica, Europe, and the U.S.A. Anyways, this may be a Special Paper worth checking out.

Geology Hike Through the Gallatin Petrified Forest

2006-04-03T10:06:00.000-07:00

I've just finished a vidcast - about 21 MB in size - of a hike in the Gallatin Petrified Forest, southwestern Montana. The vidcast can be downloaded at this link: Petrified Forest . It's in the mpeg4 format, so Quicktime is the viewing platform. More info on this particular hike can be found in our pdf on the Petrified Forest (see our Field Trips web page on Earthmaps)- but the vidcast is a good overview, complete with photos, maps, and audio. You can also just link directly to Geopostings's Podcasts to get the vidcast. Enjoy.

A Walk in the Woods

2006-02-28T07:28:00.000-08:00

The New York Times Science News just posted a great video - it's a discussion on evolution between NY Times Jim Gorman and Niles Eldredge. Their discussion takes place partly in Central Park, and then in the American Museum of Natural History where Eldredge is the curator of the current Darwin exhibit. Link to the video by clicking on: A Walk in the Woods . Once you link to the NY Times video postings, just scroll down the video list to "A Walk in the Woods" and click on it - it will then load into your media player.

National Grid Coordinates?

2006-02-27T16:21:00.000-08:00

NPR had a brief summary of the rationale for using national grid coordinates in mapping on their Weekend Edition, 2/25/06 - http://www.npr.org/templates/story/story.php?storyId=5233408 . The story was mainly focused on emergency/disaster events, and the problems encountered with everyone using either a different grid system or just still using street addresses. NOAA has a web site that further explains the national grid system - http://ngs.noaa.gov/TOOLS/usng.html . The NOAA site also posts interactive conversions and a conversion program for all of us who use other grid systems like UTM or lat/long. NOAA does say that although the national grid system can provide for whatever level of precision a user desires, we still may prefer to use the UTM format for applications requiring precision greater than 1 meter. Interesting...

Sequence Stratigraphy in Continental Rocks

2006-02-15T09:28:00.000-08:00

Here is an abstract on the importance of paleosols in continental sequence stratigraphic applications that we've submitted to the AAPG meeting coming up for Billings, MT in June of 2006. It's just some thoughts on the initial delineation of sequences in continental rocks:

Sequence Stratigraphy and Paleosols in Continental Rocks – Examples from Cenozoic Deposits of the Great Plains and western USA

Cenozoic continental deposits of the Great Plains and western USA can be separated into large-scale sequences that are variously marked by extensive paleosol formation, irregular topography developed on erosional surfaces, and/or angular discordance of strata. Abrupt changes in provenance or lithologies also may indicate a sequence boundary. Specifically, the interregional unconformities that bound these sequences within the Great Plains and western USA occur at about 55 Ma, 37 Ma, 30 Ma, 20 Ma, and 4 Ma. Hiatuses between sequences are variable in duration and can extend for several million years.

Paleosols are one of the more obvious sequence boundary markers. Because paleosols in many stages of formation may exist within a sequence, it is the advanced stages and pedocomplexes of paleosols that we use for identifying sequence-bounding surfaces. Calcic pedocomplexes are particularly useful in areas of arid to semi-arid climatic regimes, and in fact delineate four of the five large-scale sequences identified throughout the Great Plains and much of the western USA. The calcic pedocomplexes are readily identifiable on the surface with a pedocomplex typically being several tens of feet thick and containing several partial soil profiles. In the most complete scenario, an individual profile may contain an argillic or argillic/calcareous (Bt or Btk) horizon, a K horizon, and a C horizon. The calcic pedocomplexes also possess distinct physical properties that aid in subsurface identification. The combined density and velocity differences between paleosols and non-pedogenic strata result in bright reflections on seismic sections and distinct well log signatures.

Musings on a Winter Day

2006-02-13T13:35:00.000-08:00

I'm just wondering about the usefulness of the online course concept for intro geology courses. After having written content for an 8th-9th grade level course, I'm left with the thought that geology is an observational science - at least for intro content. It would be interesting to compare what is taken from the course by kids that have done only an online course in geology with those that have taken a comparable course strictly in the classroom.