The bedrock that acts as Long Island's foundation was formed by the restless movement of the Earth's surface. The Earth's surface is composed of large pieces of crust and mantle material (lithosphere) called tectonice plates. These tectonic plates move along a conveyor belt of "putty like" mantle material in a layer called the asthenosphere. At one time in the Earth's history, all of the Earth's continents were grouped together to form a large supercontinent known as Pangea (SEE FIGURE 1). North America was once located near the equator where the climate was tropical. If you look closely you'll notice that North America was rotated to the side. Thus the east coast of North America was aligned with the northwest coast of Africa. A volcanic island chain lurked off the North American coast. Approximately 450 million years ago (mya), the North American Coast collided with this chain. This volcanic chain was forced into the deep into the Earth's crust because of it's heavier density. The intense heat and pressure of this movement hardend the rock. This rock would eventually become the bedrock and the foundation of which Long Island would be created.

*Click on Figure 1 to see how Pangea seperated. Click on view animation for "2.1- Wegner and Continental Drift"

Approximately 150 million years later another event would occur that would impact the formation of Long Island. If you look closely at Figure 1, you'll notice that North America and Africa were extremely close together. As the tectonic plates continued to move, these massive continents would eventually collide with one another. Over the course of the next 100 million years, North America and Africa would contine to push into each other. The continents applied so much pressure on the rocks, the rocks were forced to buckle and fold upwards. As a result, the landscape became elevated. In the midst of this 100 million year event, a mountain range would begin to form on both the eastern coast of North America and on the North Western coast of Africa. Today we call these North American mountains the Appalachain mountains. Eventually over time, North America and Africa would move away from each other in a process called sea floor spreading. This process created new ocean floor. As a result, the ocean floor between North America and Africa got bigger. As the ocean floor got bigger, the ocean we now call the Atlantic Ocean also grew. The Atlantic Ocean will play a large part in the geological change of Long Island

Over time, rivers formed and ran down from the Appalachain mountains. The erosive powers of the rivers cut a large valley into the rock much like the Colorado River cut through the Grand Canyon. This newly formed valley would eventually become what we know today as Long Island Sound.

The rivers that formed Long Island Sound also eroded sediments from the Appalachain Mountains. These sediments would then be deposited on top of the bedrock that had been formed 250 mya. The sediment still exists today and plays a vital role in mainting our underground water supply.