Geology Of The Grand Canyon

The Grand Canyon is always changing. The layers of the Grand Canyon provide a window into two billion years of the Earth's history.

The rock formed from sediments is thousands of feet in thickness. Around 1.8 billion years ago, geological forces uplifted and crumpled this rock to create a mountain range that was probably 6 miles high.

The enormous pressure and heat recrystallized the rock to schist and gneiss. Molten lava from inside the earth forced itself into the rock and hardened into veins of pink granite. Over millions of years, water and wind eroded the mountain range into a plain and a primordial sea then submerged it. Sediments sank to the bottom of the sea, solidified into rock, magma continued to push up from the center of the Earth.

Around a billion years ago, the Earth moved again. The crust cracked into giant fault blocks that tilted upward. This formed a second mountain range. Again, the wind, rain, and frosts, eroded away these mountains over millions of years.

Most of the rock in the Grand Canyon that is visible today accumulated over the schist and gneiss in the last 525 million years. During some of that time, the region sank beneath the sea and primitive shellfish fossilized in sea bottoms that hardened into shale.

During other periods of time, the area rose again. On top of the Grand Canyon today, at around 8,000 feet elevation is the youngest cream-colored limestone layer. Known as Kaibab limestone, this layer is about 300 feet thick and is formed from the remains of coral, sponges, and other marine animals.

About 6 million years ago, the Colorado River began to flow across the region and started to carver the upper layers of the canyon. Over the centuries, eroding away inch by inch, the river eventually reached the basement rocks 4,000 feet below the rim. The water continues to erode the huge gorge, enlarging and deeping the walls and floor of the Grand Canyon.