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Paleozoic Era
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Cenozoic Era |
Pleistocene Period
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New Hampshire was once covered by an inland sea. Over time, sand, silt, and mud-lime was deposited on the sea bottom. This sediment was gradually buried, pressed together, or compacted, and forced together into sedimentary rock layers. These rocks are made from other rocks, plants and animals. When pressure squeezes water from the particles, the particles are clumped together forming the sedimentary rocks. |
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Plate movement below the earth's surface is constantly moving. The internal pressure below the the inland sea caused the land to rise. The inland sea began to moved back, as the land was pushed up. The sedimentary rocks, which were at the bottom of the sea, were forced up into mountain-like folds (folded mountains), as the earth's surface is squeezed together. The pushing and squeezing of the sedimentary rock created layers of metamorphic rock formations. Metamorphic rocks were either igneous or sedimentary that have changed in appearance through pressure and heat. The White Mountains are these type of rock. At the same time, volcanic action, from thousands of feet below the earth's surface, caused the molten rock to push upward into the cracks in the crust. This volcanic action caused the formation of our granite rocks, which are igneous rocks. This rock has become solid, from the molten stage, either inside the earth or on the surface. |
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After the land surface stopped changing and erupting, the land began to collect soil. Plant succession began to take place. The natural process of weathering and erosion began to occur. The granite, beneath the topsoil, was exposed. About 1 million years ago, the climate of the earth was going through a cooling period. Mountain glaciers were forming in the White Mountain snowfields. The snowfields never melted, because the temperatures were too cold. More snow packed together, which slowly became "rivers" of slow-moving ice called glaciers. In far northern Canada, large masses of ice were also forming. These were known as continental ice sheets. The Wisconsin Glacial Stage, 50,000 years ago, moved down from Canada and covered New Hampshire's landscape. This Continental glacier carried rocks and soil within the ice. Every time the glacier melted it dropped dirt, small rocks, and boulders. Geologists think that the glacier expanded and retreated four times before melting 12,000 to15,000 years ago. |
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