M&M Section 5

September 6, 2012:  A 5.7 mile return to the hike-and-back means a long day.  But now north of US202, we are in land owned by Holyoke Community College and a sportsman's club, so its back to single-track trails (no more mountain bikes or ATVs).


OK, time for everyone's favorite subject: geology.  Imma drop some science!

I mentioned that the ridge we are following is basalt, with its origins as lava.  Which means the Connecticut Valley once had volcanoes!  Well, at least big cracks in the earth where lava seeped out.  How did this happen?  About 200 million years ago, the super-continent of Pangea began to pull apart, with long cracks or rifts appearing as North America and Europe/Africa separated.  One of these rifts eventually became wide enough to fill with ocean water and form the Atlantic - it's still spreading today and the Atlantic grows wider by about an inch every year.  Another of these faults  formed just to the west and opened wide enough to form the Connecticut Valley.  That fault - called the Eastern Border Fault because it runs along the eastern side of the valley - is still there, running between Keene, NH and New Haven, Ct and beyond, but hasn't been active for 10's of millions of years now.


It must've been very scenic when the valley was new - to either side were giant mountain ranges, and within the wide valley, plains and lakes and sandy beaches formed.  The Valley looked not unlike the rift valleys of East Africa, famous for their herds of elephants and wildebeests and lions, etc.   Only, the ancient Connecticut Valley had dinosaurs.  Their footprints appear on the shores of those lakes and can be seen in many places, including Holyoke and Connecticut's Dinosaur State Park.

The big footprint in the photo to the left is along Route 5 north of Holyoke and was made by a Dilophosaurus - remember the spitting dinosaur that gives it to Newman in Jurassic Park?

Over the course of millions of years, the valley filled with new rock layers.  A few times, the fault system oozed out hundreds of feet of lava covering large areas - that's the basalt we're walking on.  Still, the mountains on either side continued eroding and thousands of feet of new sediments soon covered the basalt.  Earthquakes along the fault tilted the new rock layers about 25 degrees, downward to the east.  But eventually all this activity stopped and the valley completely filled and the mountains on either side eroded down and everything in western Mass and Ct was a level plain.  Except Mount Monadnock, which continued to poke up above everything just as it does today.  More on that tough mound of rock later.

More recently, rivers and glaciers re-formed the Connecticut Valley, eroding the soft sedimentary rocks to form the low wide valley we know today.  The hard roots of the ancient mountains on the side of the valley now form the Berkshires and the mid-state highlands.  And the edge of that layer or two of hard basalt, because of the tilting from long ago, now pokes up above the valley floor too, forming our ridge and giving it the distinctive cliffs on the western side and gentle slope to the east.

Let this sign from the Mt Tom visitors center show you - i drew the M&M in red.  The current section is just below where this cutaway drawing starts:

Ok, enough science!  The hike in this part was delightful despite the cloudy weather - several views and great deep woods that feel very remote despite being mere miles from Holyoke and its suburbs.  Here's a shot looking south, where you can see the eastern gentle sloping side of the ridge (that 25% tilt) and the western cliff side, especially on that far hill from Section 2: 

Hiking in New England, one often comes across random giant boulders like we did, called an erratic:

This guy, which isn't basalt like the rocks it is sitting on, traveled with the giant ice sheet that once covered the northern part of the US.  He was plucked up somewhere well north of here and left at this spot as the ice melted from under it.  National Geographic just had an interesting essay about erratics a month or so ago, with this nice shot of Glen Rock in Glen Rock, NJ.



OK, FOR REALZ, NO MORE GEOLOGY.  Though, it is kinda cool.

 Today: 5.7 trail miles.  M&M completed: 19.3 out of 114 mi.