GWRLT: Geology of Southern Maine

GWRLT: Geology week 1

Ten years ago, I started working at the University of New Hampshire because staff can take classes for free. I’ve always wanted to take an Earth Science course, especially Geology, but most classes in this department are in the morning, and I can only attend classes after 2 pm. 

Recently, I was excited to find out about a Saturday morning geology class offered by Great Works Regional Land Trust, taught by retired Dover High School Earth Science teacher Don Wason.

 

Week One, we met at the GWRLT office at Beach Plum Farm, where we learned the basics of mineral and rock identification, focusing on coastal Maine.

It was a great experience, and I’m looking forward to this Saturday’s field trip at Nubble. Next week, we’ll visit Marginal Way in Ogunquit. It’s wonderful to combine geology, education, and being outdoors, and I can’t wait for more weekends like this. 

GWRLT: Geology week #2

Saturday in my GWRLT Geology class, we headed to a Nubble Light field trip for our second week of instruction. I thought I was ready for the day, but it turned out to be pretty chilly and very windy. Photos with hoods up don't make for the best visual, but hats and mittens were necessary to stay warm.

Our teacher, Don Wason, began the session by explaining that Nubble Island and Sohier Park are part of the Cape Neddick Gabbro Complex, a fancy term for the geologic event that formed the Cape and this area of Maine. This formation happened about 119 million years ago when a bubble of magma rose to the surface. Historical mapping of the rocks revealed that they formed as a bubble of magma, a sphere with the apex being Cape Neddick Hill to the northwest of the lighthouse.

Feldspar dike

One interesting thing Don pointed out is that the vertical rock layers at the lighthouse aren’t formed horizontally and then uplifted, as I had assumed. Instead, these rocks probably formed on the sides of a magma chamber, staying in place while erosion shaped them depending on their mineral composition. There is also evidence of later magma intrusions, creating features like dikes and sills made out of basalt, breccia (also called puddingstone), and other materials. I’ve visited Nubble many times, but I never really thought about the great variety of rocks present there. There are large features and small, composed of rocks and minerals.

Magma chamber layering

Feldspar sill

Don, who is a retired high school science teacher, probably gets psyched when all of his students are actually excited about the subject.

Erosion of Granite

Feldspar dike

Basalt dike

Hornblende crystals

Tafoni erosion

Next week, we’ll meet again at Beach Plum Farm, then carpool to Marginal Way. The rocks at Nubble are igneous. It will be fun to compare them to the metamorphic rocks of Ogunquit which are part of the Kittery Formation.

Hornblende crystals

Tafoni erosion

Basalt intrusion

GWRLT: Geology week 3

April 11 was our third and final geology class of the season, and we met at Beach Plum Farm before heading to Marginal Way. Since I had to leave early for a funeral in Massachusetts, I drove myself and followed the convoy to an in-town parking lot. I think that was the last weekend of free parking until the fall. I’ve always entered the Way from Perkins Cove. This parking lot was much more convenient but probably also more expensive.

This was a beautiful day as we started our walk between hotels and cobbled beaches. The stones along the water were obviously eroded from local bedrock, considered the Kittery Formation, though the riprap below the sidewalk was obviously imported. It was fun to see the ducks in the surf and even I could identify the eiders.

The rocks in this area have such character. It was interesting to see the deformation and erosion, obviously different types of stone. There were many places where the igneous basalt had pushed through. Tom told us that basalt is softer than the surrounding quartzite so it erodes faster, causing trenches, and high in iron, so it tends to rust when exposed to oxygen at the surface.

Coltsfoot flowers are considered invasive by many but before the leaves take over, the flowers that tend to come out before others are quite picturesque.

Along the way we often saw small intrusive igneous veins, often of pure quartz.

At some points the glacial striations and polishing are visible, always running southeast. Because relatively recent geologic activity is part of the story as well.

It was a great day to be at the ocean learning!

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