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New England Geology |
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The New England landscape, as we see it, is left from the age of the glaciers. |
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Long before the Ice Age, several billion years ago, the earth cooled and shrank, and its crust wrinkled, throwing out towering mountain ranges. The friction and pressure of this "wrinkling" was so intense that sand turned to marble, and limestone to gneiss and schist. Molten rock (magma) flowed from the planet's boiling core through faults in the folded crust, but the magma never made it to the surface. Instead it snaked its way into fissures, sometimes reaching a great open "bubble" of air in the crust, filling it. Then the molten rock cooled slowly, insulated beneath the earth's crust, and its liquid minerals slowly took on the crystalline texture we identify as granite. The results of this geological wonderwork are easily visible throughout New England today—in Vermont's vast quarries of creamy marble, around farmers' fields in the stone fences made of textured gneiss flecked with shiny mica, and in the great domed hills of metamorphic rock (like southern New Hampshire's Mount Monadnock) that were formed deep within the earth.
The lofty mountains
formed aeons ago were worn down, subjected to pressure
again and again, stretched and mangled, beaten and
weathered. Finally they were only a fraction of their
former height, yielding today's New England of gentle
valleys and easily climbed mountains: New Hampshire's
White Mountains, Vermont's Green
Mountains, and Massachusetts'
Berkshires. An enormous blanket of ice slowly moved southward over New England, plowing up the soil, and absorbing dirt and rock into itself by a slow-motion churning. As the climate warmed and the ice retreated, it dumped this debris into long mounds called drumlins, of which Boston's Bunker Hill is perhaps the most famous. The ice's bulldozing action also formed thousands of glacial lakes and ponds, including Thoreau's Walden Pond in Concord MA, with a unique geology. Across the landscape, huge boulders picked up and carried by the advancing ice were dropped helter-skelter as it retreated. You will come upon these glacial erratics, as they're called, which stand naked in flat fields where they don't seem to belong. The glaciers came and went, sculpting the terrain of New England at least four times. When they finally retreated, 10,000 to 20,000 years ago, the sea flooded in to cover much of the region. Melting ice added to the oceans' volume, and the weight of the ice had depressed the low terrain beneath the new sea level. But the land rebounded, reaching the level it has today, the oceans retreated, and New England became the New England we know.
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Above, tranquil
pond near Guilford CT.
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