Fire and Ice: Boston Harbor Geology / Oct. 10, 2020 (L3)

[Joseph Berkovitz]

Fire and Ice: Geology of the Boston Harbor Islands
Saturday, Oct. 10, 2020
NSPN Trip Level 3

Note: This trip is at least 12 nautical miles in length, with exposed ocean portions, crossing a busy shipping lane, currents of 1 knot or less, and rocky beach landings. We will not cancel for rain or for moderate-water conditions. Big conditions or storms will cancel, and we will work out an alternate date.

We paddle all the time in rocky environments, and the rocks all have a story to tell. Some of the stories are millions or billions of years old. But how often are we able to read and appreciate these narratives?

This trip will allow paddlers to see, touch and understand the stories written in the geology of Boston's Outer Harbor. Launching from the Winthrop Boat Launch, our goal will be to visit Lovell, Little Brewster (subject to OK from the Coast Guard), Calf and perhaps Green Islands. The tide will give us an assist in and out, with low water occurring roughly at midday. Along the way we'll stop, examine and discuss specific land and water features, and find out what they have to tell us.

Boston Harbor is an especially fertile place for such an exploration. It has been shaped by extreme events: ice ages, molten rock, tectonic rifts and continental collisions. We will view ancient bedrock features that reflect the formation and breakup of the supercontinent Pangaea, hundreds of millions of years ago. One of its pieces — “Avalonia” — eventually became part of Boston, including some of the harbor islands. Boston Harbor is also the only drowned drumlin field in the United States, with streamlined landforms of sediment that reflect the most recent ice age and the ensuing sea level rise. We will review the rough processes by which these landforms took shape, and are still being actively shaped today.

Bob Levine (screen name: rylevine) and I are jointly organizing this trip. I would like to thank George Planansky for his many observations and thoughts that have informed my understanding of this area.

To keep this trip safe we will be limiting the number of paddlers. Please sign up using this form and I will confirm with you via email (the form does not automatically stop working when the limit is reached):

https://forms.gle/oKsoGYLLRTJuwVbV9

For a deeper introduction to the geology and history of the area, please take a look at the following National Park Service document, Boston Harbor Islands National Recreation Area: Geologic Resources Inventory Report. This report provides our reference for the geology content of the trip.

http://npshistory.com/publications/boha/nrr-2017-1404.pdf

Tidal Predictions at Deer Island Light:

2020-10-10 05:48 AM    slack    -
2020-10-10 09:06 AM    ebb    -0.84
2020-10-10 12:06 PM    slack    -
2020-10-10 02:18 PM    flood    0.94
2020-10-10 05:54 PM    slack    -

[Joseph Berkovitz]

This trip has now been moved to 10/17 due to high winds today.