Geologic & Human History
Mount Mansfield and the Green Mountains are a part of a great range of mountains that stretches from Alabama to Newfoundland and even beyond North America to Greenland and the British Isles. The types of rocks around Mount Mansfield and the way they have been folded, broken, and changed by intense heat and pressure reveal a history that extends across hundreds of millions of years - all part of the grand "plate tectonics" story in which 100 kilometer-thick "plates" move one or two inches a year carrying continents across the Earth.
Sendiments to Mountains
About 400 million years ago, when the forces of plate tectonics had not yet carried the North American continent out of the Southern Hemisphere, a chain of volcanic islands collided with the eastern shore of North America. The island chain scraped and uplifted ocean sediments to create the Green Mountains.
Changes in the Rocks
The intense heat and pressure of this mountain-building event metamorphosed the ocean sediments causing their minerals to recrystalize. A common green mica named chlorite is present in many of the rocks of Mount Mansfield and the rest of the Green Mountains - it's this green rock color that gives the mountains their name. Flow within the rock during recrystallization caused minerals to migrate into discrete bands. Look for these wavy bands of mineral layers, called foliation.
Mountains Back to Sediments
In the absence of further uplifting, the constant force of erosion by wind, water, and ice has removed as much as fifteen kilometers of rock. Areas like Mount Mansfield stand higher today because the underlying rocks are physically and chemically tougher than those under the valleys.
The most recent major erosional events have been the advances and retreats of continental glaciers (like those today on Greenland) that were thick enough to completely bury Mount Mansfield. The leading edge of the most recent continental glacier melted back to the north around thirteen thousand years ago. The newly exposed rocky landscape showed marks of the mile-thick glaciers: widened U-shaped valleys and smoothed hilltops. Under its own massive weight, the glacial ice had flowed southeast toward the sea, carrying the rocks and sand that formed Long Island and Cape Cod. Look for scrape marks, two-inches wide and several feet long on the ridgeline where rocks were dragged like sandpaper across the bedrock.
Abenaki Indians called the mountain Moze-o-de-be-wadso (mountain with the head of a moose). In 1772 Ira Allen, brother of Ethan Allen, crossed the ridgeline while surveying the town of Mansfield. Nearly 100 years later, in 1859, William Henry Harrison Bingham sold 400 acres along the ridgeline to the University of Vermont for $1,000. The deed stipulates that the land be used for scientific purposes.
In the face of fifty thousand visitors each year, summit caretakers from the Green Mountain Club patrol the ridgeline to assist hikers and protect the fragile summit ecosystem. Pressures to meet demands for expanded telecommunication facilities, ski trails, and other uses need to be balanced with protection of this unique environment. Ongoing research includes assessment of alpine plants as well as migratory birds that breed in the high-elevation forests of Mount Mansfield.
Reference: The Tundra Walk: An Interpretive Guide to the Mount Mansfield Alpine Region
- Mt. Mansfield Auto Toll Road Parking (1.5/2.5) This is the most expensive option at 24$ per car. However, the complete hike will be 2.2 miles in and out.
- Underhill State Park Parking (1.5/3.5) This is the cheapest option at 2.50$ per person. However, the complete hike will be 8.8 miles if performed via a loop hike. Please note that camping options are available at this parking location.
Note: Please see the tracklog to the right. This Earthcache only requires the hike outlined in Yellow. If you combine both the Yellow and Red tracklogs, this is the hike that can be expected using Option 2 above via a loop hike.
- Find an example of foliation and post a picture with GPS coordinates. What is the distance between folds?
- Find an example of scrape marks where rocks were dragged across the ridgeline bedrock and post a picture. Which way were the rocks moving?
- Post a picture of yourself with GPS on top of Mount Mansfield with the benchmark clearly visible.
Note: All answers should be emailed to the cache owner.
|Picture 1: Foliation Example
||Picture 2: Scrape Mark Example
||Picture 3: Mount Mansfield Benchmark Example
Note: In Picture 2, the scrape marks on the rock in the lower right hand corner are indicative that there was movement of harder rock across it. However, the logging requirements are to find an example on the ridgeline bedrock (ie, not on a erratic).