History

Supercontinents, ice ages, and the hills of Ipswich

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In April of 1624, Captain John Smith of Virginia sailed near Ipswich, about which he recorded, “Here are many rising hills, and on their tops and descents are many corne fields and delightful groves… There is also Okes, Pines, Walnuts and other wood to make this place an excellent habitation, being a good and safe harbor.” News of the pleasantness of the Indian village, its good land and rich fisheries spread abroad. The Pilgrims, shivering in their rude huts at Plymouth, debated whether they should not migrate at once to this land of promise. Some of them “urged greatly the going to Agawam, which they heard to be an excellent harbor for ships, better ground and better fishing.”

In 1633, John Winthrop Jr. led a group of settlers to the Native American area known as Agawam, and began building the town that they would name Ipswich. The settlers chose a spot with granite outcroppings as a worthy location for their meeting house. It is still known today as Meeting House Green or the North Green. Imprinted in the rocks in front of the First Church in Ipswich is a xenolith, better known as the “Devil’s footprint,” created 400 million years ago when our Town Hill was part of a chain of volcanic islands. Yet most of the landforms in our town were formed less than 20,000 years ago.

Supercontinents

Map of Rodinia
Map of Pangea

When the supercontinent Rodinia broke up 750 million years ago, the Laurentian craton became the early North American continent. Other pieces reassembled in the Southern Hemisphere into a new supercontinent, Gondwana.

Eventually Gondwana reunited with Laurentia to form Pangaea, the third supercontinent. The early stages of this collision created the Appalachian chain, including the Taconic mountain range that separates Massachusetts from New York State.

The breakup of Pangaea 200 million years ago defined today’s North America and created the Atlantic Ocean.

The Avalon Terrane

North Shore terranes

The Merrimack, Nashoba, Avalon and Meguma terranes that make up the eastern half of Massachusetts are believed to have been volcanic island chains that broke off the super continent Gondwana and collided with Laurentia between 550 and 370 million years ago.

Ipswich and Cape Ann are in the Avalon Terrane , which was part of the microcontinent Avalonia during the Paleozoic era.The granite underlying the Avalon land mass crystallized while the volcanic chain was still attached to Gondwana.

Ice Ages

Earth has experienced ice ages for at least half of its existence. The Laurentide Glaciation, part of the Wisconsinian ice sheet, began its advance about 80,000 years ago, eventually covering all of New England. Water was locked up as ice, which caused the sea level to be about 300 ft. lower than it is today. As it moved over the landscape, the glacier scraped up and transported rock and soil. Its retreat 20,000 years ago left glacial land forms that dominate our landscape:

  • Moraines are linear mounds of debris that build at the toe of the glacier. Cape Ann is broadly defined as the rocky 160 square mile area between Rockport, Danvers, Ipswich and Manchester by the Sea, and is a terminal moraine.
  • Eskers are long sinuous ridges of debris deposited by streams of glacial meltwater. Various trails in Willowdale State Forest, Appleton Farms near Cutler Road and the Ipswich River Sanctuary follow the crest of eskers.
  • Drumlins are elliptical hills formed when moving ice scrapes glacial material as it moves over it, eventually leaving a tear-shaped pile up to 200′ high when the the glacier recedes. The Necks, Castle Hill and Bar Head at the southern tip of Plum Island are excellent examples of Drumlins.
  • Glacial erratics are large boulders carried by the glaciers. These are most obvious in the area from West Gloucester to Rockport.
  • Till is the unsorted glacial debris deposited directly under the glacier. It constitutes much of the soil in this area.
little_neck_1900
Little Neck and Great Neck are glacial drumlins. Photo circa 1900 by George Dexter
shipwreck_steephill_dexter
Wreck of the Ada K. Damon below drumlins Castle Hill and Steep Hill.
View of Bar Head from Crane Beach
View from Crane Beach of Bar Head, a glacial drumlin at the tip of Plum Island
Ipswich River Wildlife Sanctuary
The North Esker at Mass Audubon’s Ipswich River Wildlife Sanctuary

The animation below shows the ebb and flow of the Ice Ages over the last 120,000 years. The timeline in the upper right corner is measured in thousands of years before the present (kaPB).

Post-Glacial Rebound

The sheer weight of mile-high glacial ice caused our 450,000 granite bedrock to sink. Then as the glaciers melted, the sea level rose, putting much of the North Shore under water. As the ice-free land began to decompress and rebound upwards, the ocean receded to the shoreline we see today. Much of the surface soil in our area was deposited during the post-glacial period by these events. Marshland, drumlins and bedrock hills mix with broad flat areas of marine sand, gravel deposits and glacial till, creating the landscape of Ipswich and the North Shore area today. The Topsfield hills, Great Neck and Castle Hill are but a few of the local geological features left by the retreating glacier.

Native Americans began moving into New England after the retreat of the Wisconsin Glacier, around 12,000 BC. In the early 1950’s, a group of young amateur archeologists men now known as the “Bull Brook Boys” discovered one of the largest Paleo-Indian sites in North America along the banks of the Egypt River in an area being cleared for a sand and gravel operation on Paradise Road.

The hills of Ipswich

The photo above is a view of Heartbreak Hill taken from the roof of a building on North Main Street in 1879. The woolen mill is gone now, and Heartbreak Hill is covered with trees. The Ipswich River wraps around Town Hill, a granite monolith that is millions of years old, but most of the hills in Ipswich are glacial drumlins left as the ice age glaciers retreated about 20,000 years ago.

Hills in Ipswich Massachusetts

Bartholomew Hill, 204′: off Linebrook behind Doyon School
Bear (Boar) Hill: off Topsfield Road near Little Turner Hill
Bush Hill, 193′: off Topsfield Road
Castle Hill, 165′: at end of Argilla Road
Elm Hill: Marini’s
Heartbreak Hill: off Argilla Road 164 ft.
Jewett Hill, 212′: off High Street at Rowley line
Little Turner Hill, 197′: off Topsfield Road
Plover Hill: Great Neck
Prospect Hill, 262′: Ipswich/Rowley line
Sagamore Hill.172′: Ipswich/Hamilton line
Scott Hill,180′: off Topsfield Road
Steep Hill: off Argilla Road facing Crane Beach
Tilton’s Hill: near Treadwell Island
Town Hill, 184′: east of town center
Turkey Hill, 240′: between Pineswamp & Topsfield Road
Turner Hill, 250′: off Topsfield Road
Vine Hill: off Topsfield Road (Masonic Temple)
Windmill Hill: County & Essex Roads (Cable Hospital)

Bedrock geological map of the Ipswich Quadrangle

Ipswich MA bedrock US Geological Survey
Bedrock geologic map of the Ipswich quadrangle, 1698 By: William H. Dennen. Ordovician rock underlies the southern 2/3 which includes the town of Ipswich. A minor fault follows the general course of the Ipswich River. 
Color-coded explanation chart for the Ipswich bedrock map
Color-coded explanation chart for the Ipswich bedrock map

Superficial geology of the Ipswich Quadrangle

USGS Geologic Quadrangle Map GQ-189
USGS Geological survey of the superficial geology of Ipswich. Yellows are beach, dune and alluvial sand and gravel deposits. Oranges are ice-laid drumlins and moraines. Greens are marine and estuary deposits, and pinks are glacio-fluvial deposits. The bedrock underlying these superficial deposits are two batholithic complexes from the Devonian and Carboniferous periods.

Sources and Further Reading:

The excellent book Roadside Geology of Massachusetts explains how sparkling beaches, tidal estuaries, and granite headlands ornament the Massachusetts coast, while giant folds of gneiss and schist crisscross the interior, squeezed up between colliding continents like toothpaste from a tube. James Skehan explains the geologic history behind the rocks and landforms visible from the state’s highways, including such well-known historic features as Bloody Bluff, Beacon Hill, Plymouth Rock, and Walden Pond. Interspersed through the guidebook are tales of pioneering geologists such as Harvard’s Louis Agassiz, the first to propose that continental glaciers–not the remnants of Noah’s Flood as early settlers had imagined–polished the state’s bedrock and deposited its enormous boulders and sand plains. Numerous maps and photographs reveal ancient volcanoes, marble potholes, colorful minerals, dinosaur footprints, and America’s first commercial railroad–built with blocks of Quincy granite. Geologic road guides include tours of Boston Harbor Islands National Recreation Area, Cape Cod National Seashore, Nantucket, Martha’s Vineyard, and Mount Greylock State Reservation.

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