Dino Bones in New England

Dear Doc Rock,
     My family had a great road trip to the western US last summer. The kids (7 and 10) became rabid dinosaur nuts after seeing fossils at Dinosaur National Monument in northwestern Colorado. What a fabulous place to visit. Fossil bones were being excavated right in the visitor center.
     Did dinosaurs only live in the western part of North America. Is their anyplace close to our home in New England to see dinosaur fossils?

Jake Orr
Pittsfield, Massachusetts

Dear Jake,
     I became a dino-nut at about the age of your youngest. I still have a couple of books from that era of my life, which I'll admit was not all that long after the poor brutes went extinct. I'm pretty sure it was my early interest in dinosaurs that led me to become a geologist, and look where that got me! Now I'm on the internet and I have a blog. Great things await your dino-nuts!
     Dinosaur fossils are known from across North America, as long as the rocks are 1] of the right age, 2] exposed through erosion, and 3] those rocks have not been metamorphosed or too badly destroyed by faulting or intrusions. The western USA and Canada have the best combination of rocks and conditions to preserve dinosaur fossils. This website from the Washington State Department of Natural Resources lists some place to see dino fossils in the wild. It is sort of ironic, since no dinosaur fossils have (yet) been found in Washington.

Dinosaur tracks at Dinosaur State Park, Connecticut. Photo by Ken Zirkel (LeKriz). More  photos on Flickr

     Hmmmm, dinosaurs in New England. Massachusetts and Connecticut are famous for preserved dinosaurs foot prints. Dinosaur Footprints Reservation just north of Holyoke, Massachusetts is a famous dinosaur footprint site. There are hundreds of tracks preserved on sandstone slabs. They were left by a probable carnivorous dinosaur about 15' long of an unknown species- no fossil bones have been found with the tracks to identify the animal. The foot prints were given the scientific name Eubrontes giganteus. They were found in 1802, and are the first North American dinosaur fossils described by scientists. That alone makes the Heritage Reservation important. Visit their website for directions and information.

Eubrontes fossil dinosaur tracks at Amherst College.

    Dinosaur State Park in Rocky Hill, Connecticut also displays trackways. Kids can make plaster casts of these tracks to take home. Check out the Park's website. Learn about the track casting at another Connecticut State Park website.
     The Beneski Museum of Natural History at Amherst College has a wonderful exhibit of extinct animal fossils, and the original dino tracks salvaged from the Connecticut valley. (I've been there, very cool for kids.)

What's the difference between the Sierra and Cascade Mountains?

Dear Doctor Rock,

Why do we call the mountain range in California 'The Sierra Nevada' and the ones in Oregon and Washington 'The Cascades'? What is the difference?

Rita Bjornstein,
Topeka, Kansas

Dear Rita,
They are two geologically and geographically separate mountain ranges. The Sierra Nevada (the 'Snowy Range') are older than the Cascades, and were once volcanic. Between about 220 and 15 million years ago, there was subduction off the coast of California- the now-extinct Farallon Plate slid beneath the west-moving North American Plate, and a range of volcanic mountains rose where the Sierras are. The famous granite of Yosemite, Mount Whitney, and elsewhere in the Sierras was once the magma in the crust that fed those volcanoes. Subduction migrated northward up the coast of the continent, and the volcanic rocks that once covered the surface in the Sierras are mostly stripped away by erosion to expose the guts of the silenced volcanoes.
The Cascades are still an active volcanic chain and result from subduction of the Juan de Fuca Plate beneath North America. This volcanic chain is around 40 million years old. They extend from Lassen Peak in northern California through Oregon and Washington and then for another 125 miles north of Vancouver, British Columbia. (Yes, there are many volcanoes in British Columbia!) Subduction still occurs off the coast parallel to the Cascades chain, and as long as it continues, magma will be generated beneath the North American Plate and volcanoes will erupt in the Cascades.
Click here to see an animation about subduction and some more explanation. There is a great YouTube video showing the subduction of the Farallon Plate, the migration of subduction northward, and the end of subduction in California. The author, Dr. Tanya Atwater, is a pioneer is this geology.

Dr. Rock


The Cascade subduction zone. The thicker continental plate overrides the

ocean plate. The colored dots represent earthquakes. Volcanoes can grow once

the subducted ocean lithosphere (rocky crust plus strong upper mantle) have

descended far enough into the soft asthenosphere (weaker mantle).