G6- The Grand Canyon: A Window to Earth’s History 800-900L -04
Around 75 million years ago, the entire region was uplifted. It rose an estimated 2 miles. This increase in elevation changed the drainage patterns of the area. A new, larger river formed and captured the ancient Colorado River. This new river started to cut its way into the Colorado Plateau.
Around 2 million years ago, Earth entered the Pleistocene Epoch. During the Ice Age, as it is commonly called, glaciers covered major parts of North America. These glaciers made a number of advances southward. During this period of time, the area had a wetter climate. This resulted in an increased flow of water in the Colorado River. With an increased flow and a steep stream gradient, the river was able to carve a deep canyon. It is this canyon we see today.
Around 1.8 million years ago, a series of volcanic eruptions covered the area in lava. The lava cooled, creating many natural dams. These dams blocked the flow of the river. Eventually, the river cut its way through the natural dams. By then, the Ice Age had passed. The wet climates associated with the Ice Age were now in the past. With the start of the Holocene Epoch (the current epoch) came a more arid climate. This change reduced the Colorado River’s ability to carve a deeper canyon.
Conclusions
Today, millions of tourists flock to the Grand Canyon. They come for its majestic views. Some take a mule ride down to the Colorado River. On the way, they pass some of the oldest rocks in the region. Most people look at the banded layers of sedimentary rocks and are amazed at their sheer beauty. What they do not realize are the scientific implications. For the geologists who study the region, the Grand Canyon is one of the best laboratories on Earth.
