By Jaelyn J. Eberle, University of Colorado Museum of Natural History and Dept. of Geological Sciences, Boulder, CO.

The Early Eocene marked the peak of global warming since onset of the Cenozoic Era (ca. the last 65.5 million years), when mid-latitude mean annual temperatures soared, and the High Arctic was home to lush swamp forests inhabited by alligators, giant tortoises, and a diverse mammalian fauna that included primates and tapirs. As the relevant fossil-bearing rocks of the Eureka Sound Group on central Ellesmere Island were well above the Arctic Circle during Eocene time and only 1–2º degrees farther south than today (~77º N.), this environment experienced months of continuous sunlight and darkness, the Arctic summer and winter, respectively.

The Eocene of Ellesmere Island Tree in the Arctic (painting by Cliff Morrow, Carnegie Museum of Natural History)

By John Lufkin, Ph.D., consulting geologist

Costa Rica is located in Central America, bordered by Nicaragua on the north and Panama on the south. It is the second-smallest nation after El Salvador, and composed of almost 51,000 sq km. It is situated in the tropics, between 8 and 11 degrees north latitude. Most of the people of the country of over 3 million live in and around San Jose, the capital, located in the central part of the country. Liberia, with a population of 40,000, is the largest city in the north. I have made two visits to Costa Rica in the past two years, and have become particularly interested in the geology, sea turtles, and leaf cutter ants residing there.

Costa Rica lies at the junction of the Cocos and Caribbean plates. Consisting of heavier basaltic rock, the Cocos plate is being subducted eastward underneath the Caribbean plate. The process of subduction is widespread around the Pacific basin, where linear volcanic chains of andesitic rock are produced. The geology of northern Costa Rica is underlain by Cretaceous, Tertiary, and Quaternary rocks. Rocks of Cretaceous age include mostly shales, graywacke, conglomerate, limestone, and chert. The Santa Elena Peninsula, however, is underlain by ultramafic rock. The coastal area north of Santa Elena Peninsula is composed of sedimentary and volcanic rocks. The interior lowland is underlain by lacustrine sediments, tuffs, and dacitic lavas. The backbone of Costa Rica, forming the dominant mountain range, or Cordillera, is volcanic in origin, and consists of pyroclastic rocks, tuffs, and lava flows of andesitic and basaltic composition. Thick deposits of pyroclastic mudflows, or lahars, flank the Cordillera. The greatest tourist attraction in Costa Rica is the majestic and active volcano, Arenal, a 5-hour drive ESE of Liberia. The eruptive history of Arenal spans about 7,000 years, and includes both explosive eruptions and more effusive, lava outpourings. Over the past 4,000 years Arenal has produced tephra layers roughly every 300 years.

There are seven species of sea turtles worldwide, and the Green, Leatherback, and Olive Ridley are common visitors to the beaches of Costa Rica. The Leatherback is the largest known sea turtle, and also the one without a solid shell. On the West Coast, the Leatherback has a protected nesting site in the vicinity of Playa Grande and Tamarindo. To the south, the Olive Ridley turtle nests on the beaches of Ostional.

The Leafcutter ants form huge colonies, and can be found throughout Costa Rica. They march single file through the rainforests on trails 1 foot wide, carrying leaf sections at least twice as large as the ants themselves. The life and importance of these interesting creatures will also be discussed briefly.

By Matt Morgan

It is the time of year when field season is coming to an end and the feeling of fall is in the air. It is the time when I reflect upon what I did this summer and start to put together another geologic quadrangle map and report. For me, this past mapping season was one of the most memorable. Working east of Castle Rock, just south of the Town of Elizabeth, I gained a first-hand perspective of what geology means to people outside of the typical "ranks." These were the ranchers, farmers, artists, coffee shop clerks, and stay-at-home parents that have a keen interest in what I was doing for the Colorado Geological Survey ("THEIR" Geological Survey as our State Geologist often says). They wanted to know "where is the water?" or "is that stuff good for putting on my road?" or "how do YOU know how old that rock is?"

I found myself challenged, almost daily, and was enlightened that the folks, who effectively pay my salary, were eager to know what I was doing and why I was doing it. On a couple of occasions, I spent half a day giving interested landowners an impromptu geologic tour of their property. It is this type of close interaction makes my job worthwhile and also made me realize the responsibilities we have as geologists to educate the public. Not only does the future of our science rely upon such education, but the vitality of our society depends upon it.

I have also been getting very positive feedback for our outreach events. The turnout was excellent for the "New Insights into the Geologic and Geomorphic Evolution of the South Park Basin" field trip that was held on May 17th. Those that were in attendance were treated to a very well-run and informative trip. Thanks to Cal Ruleman, Bob Bohannon, Bob Kirkham, and Karl Kellogg for taking us on a wonderful geologic tour! And…both young and old(er) turned out for the chance to pound on rocks at the rescheduled Family Day at Harris Park on June 7. Some nice amazonite specimens went home. Thanks to Pete Modreski.

We also gained a few new members from the CSS booth at the Denver Gem and Mineral Club’s show back in February. Thanks to Lisa Rukstales, Lisa Fisher, and Sue Hirschfeld for designing the display and attending the event.

Our website is undergoing a facelift. John Ghist is working hard on making the site more user-friendly by reorganizing and simplifying the pages. John is also working with Beth Simmons on creating new CSS history pages that are very informative. Be sure to check out these pages on our website.

By Chuck Weisenberg

Every year, the Colorado Scientific Society presents special awards for the best earth Science projects at the state-wide Colorado State Science Fair, held in the Lory Student Center at Colorado State University.

On Thursday, April 10, 2008, CSM members Chuck Weisenberg and Tom Sutton judged the projects and awarded the following prizes:

First Prize: $100 Gwyneth Glissman, 11th Grade, Peak to Peak Charter School, Lafayette

"Analyzing Arctic Solar Flux and Ice Extent Loss Projections"

Gwyneth did an amazing job gathering data and modeling the use of floating reflectors on the equatorial seas to reduce global warming. A creative idea and very well done.

Second Prize: $75 Jeffrey Hibbert, 9th grade, Lone Star School, Otis

Qualitative Assay of Radionuclide Species in Ash from Coal Combustion"

Jeffrey looked for radioactivity around a coal-fired power plant near his home. Impressive work for a 9th grader.

First Prize: $75 Isaac Beverlin, 6th grade, Dolores Middle School, Dolores

"ARCHES: Solid Rock to Windows in Time"

Isaac studied the frequency of natural arches within the different formations in Arches National Monument.

Second prize: $50 Jennifer Bushnell & Kelsey Rohlfing, 7th grade, Irving middle School, Colorado Springs

"Do your rocks need sunscreen?"

The girls studied the effects of sunscreens, etc. on florescent minerals. Unusual idea.

By Karl Kellogg

Contact Karl Kellogg (kkellogg@usgs.gov; (303) 236-1305) for questions or additional information.

U.S. Geological Survey has published, "Table Mountain shoshonite porphyry lava flows and their vents, Golden, Colorado", by Harald Drewes, U.S. Geological Survey Scientific Investigations Report 2006-5242. Harald Drewes has led CSS and other field trips to Table Mountain. Now you can read, "the rest of the story."

If you are interested in leading outside bus tours and indoor exhibit tours at Dinosaur Ridge, please contact Joe Tempel at 720-971-9649 or Joe_Tempel@Dinoridge.org. Full-time or Part-time work; Hourly Wage: $10.

Newsletter Help!

CSS is seeking a person to assume newsletter responsibilities. This is a fun job! Be among the first to learn of upcoming talks and fact-filled field trips. Attend council meetings and enjoy free pizza! Most importantly, you would have satisfaction in knowing you are contributing to a valuable and enduring organization. If interested, please contact Celia Greenman at 303-291-7327, celia.greenman@state.co.us.

Earth Science Meetings and Talks

Newsletter items must be received by the 25th of each month.

Items may include special events, open houses, etc...Thanks!

27th Avenue, Lakewood. Social 6:00-7:00 p.m. Presentation at 7:00 p.m. Meetings are normally scheduled for the first Monday of each month. Sep 8, Bill Bond, Paul Bartos, Esperanza Silver Corp, "The discovery of the Cerro Jumil gold skarn, Morelos, Mexico". For information contact Jim Piper, (303) 932-0137, or the website http://www.dregs.org.

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