The Northeast was created through a series of mountain building events followed by weathering and erosion. The geological makeup of this region is complex. As a result, the wine regions of the Northeast offer a wide range of soils and growing conditions.

The Grenville Mountains

1.1 billion years ago, a mountain building event created the Grenville Mountains. The oldest rocks in the Northeast owe their existence to this period. During this event, proto-North America collided with another continent. The collision crumpled the crust, creating a tall mountain range that stretched from Canada to Mexico: the Grenville Mountains. These mountains are the earliest evidence of mountain building in our region, and the rocks remaining from that ancient mountain chain are the oldest rocks that we see exposed at the surface in the Northeast today.

Erosion wore away much of this ancient mountain range, leaving only the innermost cores exposed today. Grenville rocks are exposed in the Adirondacks, the Hudson and Jersey Highlands, Manhattan and Westchester in New York, the Green Mountains of Vermont, the Reading Prong of Pennsylvania, and the Berkshire Hills of Massachusetts. The eroding Grenville Mountains deposited sediments on either side of the range. Shallow seas covered the flat lands below the ranges. This resulted in layered sediments and carbonate deposits from fossilized sea creatures.

The Taconic Mountains

Around 500 million years ago, the plate carrying Baltica (proto-Europe) approached the North American plate from the southeast. As the continents approached, a subduction zone formed. The intense pressure created a series of volcanic islands which then collided with the North American coast, creating the Taconic Mountains. The rocks of these mountains include deep-sea sediments, the oceanic crust, and rock from the upper mantle. The island remnants are found in a thin band of rocks extending from northernmost Vermont through northern New Hampshire, and up the western and northernmost portion of Maine.

This collision also formed the Appalachian Basin, which was flooded by a shallow sea and filled in with sediments from the Taconic Mountains, forming deltas. Eventually the Taconic Mountains eroded to their inner core. The Berkshire Mountains of western Massachusetts are part of the ancient Taconics, and the oldest, most erosion-resistant blocks from the ancestral Taconics eventually became the Taconic Mountains we see today.

Creation of New England

North America at this time was missing New England. It originated from pieces of land referred to as exotic terranes which come from places other than North America and get stuck on the continent as plates converge. These pieces have different geological characteristics than their surroundings as a result. Two such terranes got attached to the North American plate during the mountain building periods, getting crumpled and smashed in the process and resulting in complex geology.

The Iapetus Terrane created most of Vermont, New Hampshire, Massachusetts, Connecticut, and Maine. This happened during the creation of the Taconic Mountains. The terrane consists mainly of volcanic rocks.

The Avalonia Terrane came from the ancient continent of Gondwana. It tacked on the eastern parts of Maine, Connecticut, Massachusetts, and Rhode Island. At this point there was still no Long Island, Cape Cod, or islands off the New England coast.