Geology highlights for hikers - Eastern Mass.

[Amicus]

Since Jazzbo's "volcano" thread pertained to the Ossipees and NH mostly, I start this new one to highlight the very interesting (to me, anyway) article posted by Dr. Dasypodidae:

Here is a short article on some choice geological excursions in the Boston area.

http://www.geotimes.org/feb06/Travels0206.html

From it, I learn that remnants of the "Boston Volcano" of roughly 600 million years ago can be found not only in the "Rim of Fire" leg of the Bay Circuit Trail in Sherborn, but in the Middlesex Fells (which I enjoyed red-lining over the last couple of years) and in Castle Rock in Marblehead Neck.

 

[Dr. Dasypodidae]

Since Jazzbo's "volcano" thread pertained to the Ossipees and NH mostly, I start this new one to highlight the very interesting (to me, anyway) article posted by Dr. Dasypodidae:



From it, I learn that remnants of the "Boston Volcano" of roughly 600 million years ago can be found not only in the "Rim of Fire" leg of the Bay Circuit Trail in Sherborn, but in the Middlesex Fells (which I enjoyed red-lining over the last couple of years) and in Castle Rock in Marblehead Neck.

Here is a link to Father James Skehan's book that Jazzbo mentions in the other thread; the Avalon volcanoes are described in the first few pages (p.8-12) and some of the related volcanic rocks on p. 50. In a nutshell, these volcanic rocks were formed in the late Neoproterozoic (late-Precambrian), say beginning around 596 Myr, as island arcs related to an offshore subduction zone from the collision of the Gondwana and Laurentia supercontinents (for an analog, think Japan today).

http://www.amazon.com/s/ref=nb_ss_g...ehan+roadside+geology+massachusetts&x=11&y=25

 

[Amicus]

Those "Roadside Geology" paperbacks look great. The two for Mass. and for NH/VT go right on my Xmas list. The Amazon reader reviews all praise their simple, non-technical writing, for those like me who have not studied geology.

Dr. D's information enabled me to Google up this website:http://206.40.172.105/intranetv2/room/room_lessons_g3/Geology/Mass_Geo_Timeline_legal.pdf, titled -When Continents Collide -The Geology of Massachusetts Timeline

Here is an excerpt relevant to that "Boston Volcano:"

600 Million Years Ago:

(1) Event -Three pieces of land break off an ancient continent called Gondwana which is near the South Pole. These pieces of land will eventually become central and eastern Massachusetts. Volcanoes form and erupt as they move northward and the ancient Iapetus Sea closes. 150 million years later, these volcanic island continents will collide and join to Laurentia. The volcanoes would become the hills of Eastern Massachusetts.

(2) Cause -At this time there are two major continents in our hemisphere -Laurentia and Gondwana. Internal heat and pressure in mantle of earth causes faults which shear off three small pieces of land from Gondwana. Scientists call these micro-continents terranes.

I can't tell who created this time-line, which I assume is at least roughly accurate. The continents of Laurentia and Gondwana somehow remind me of the Conan the Barbarian stories by Robert E. Howard that I read in my youth.

 

[Kevin Judy and Emma]

Interesting stuff

I grew up in Stoneham and spent a lot of time stomping through the Fells. Returned a few years ago and was amazed at the trail system. We had ledge in our backyard similar to that found in the Fells. As a junior geologist I'd go out and smash it with a sledge hammer looking for diamonds and jewels. Never scored.

Spent many a summer afternoon at Castle Rock soakin' up the sun and starin' off to sea. Never thought much about the geological history of it. Mostly thinkin' about girls.

In between outings I was busy reading everything Robert E. Howard ever wrote. 2nd favorite writer. Conan lives!

How does this all tie together and what's my point? I don't freakin' know!

KDT

 

[Jazzbo]

Skehan's Roadside Geology of Massachusetts

Amigo's question about the ring of fire inspired me to sit down the other night with Skehan's Roadside Geology of Massachusetts. That is one well written book. Massachusetts has been through a lot of crashes with terranes and cratons. He takes a very complex series of events and processes and explains them very well. It inspired me to fit in a hike to top of Mt Toby before going to Granny's house in Greenfield for Thanksgiving. Where I saw the very interesting Mt Toby conglomerates. But that's fodder for another TR.

There's no way to explain the ring of fire in 100 words or less. Amicus .... You'll just have to get Skehan's book and dope it out. He's really put together some great illustrations that complement his text very well.

I'm sure this chain of collisions is based on careful research, but I'll never know how geologic researchers can reconstruct continental collisions going that far back. Let's just say Massachusetts has been sliced, diced, crumpled, uncrumpled, vulcanized, moved all over the globe. How many people know that Massachusetts has (or had) coal beds? Oh yeah then there's the glaciers. He does a nice job on describing the glacial activity in Mass.

I wish the New Hampshire and VT each had their own roadside guides rather than sharing the same book. The Maine guide is good too.

 

[cushetunk]

I wish the New Hampshire and VT each had their own roadside guides rather than sharing the same book.

It's no roadside geology book, but this is a useful start for interpreting Vermont geology.

The Geology of Vermont

There are also many more good resources and maps at the Vermont Geological Survey page.

 

[Amicus]

Amigo's question about the ring of fire inspired me to sit down the other night with Skehan's Roadside Geology of Massachusetts. That is one well written book.

Protocol will prevent my reading this book before Dec. 25, but you add to the uniformly enthusiastic notices I've seen.

I've already learned enough since last week to realize that my simple-minded mental picture of a fiery Boston Volcano spewing lava in rings, the outermost of which coincided with some of the Bay Circuit Trail, was simple-minded.

 

[erugs]

Kevin said: "As a junior geologist [in Stoneham] I'd go out and smash it with a sledge hammer looking for diamonds and jewels. Never scored."


Well, I grew up in the hills of Malden and as a junior explorer used to go to all the ledges and outcroppings I could find and looked for magic "buttons" I could push that would open a door to the inner world! I never scored then, either, but I'm still hopeful.