Sample Article:
At first, the area of the Grand Canyon was an enormous plateau consisting of layers and layers of rock that were deposited over long periods of time. When powerful water, now known as the Colorado River, began to flow over it, the rock eroded leaving a most wondrous canyon that we call the Grand Canyon.
Scientists don’t have all the details as to how the Grand Canyon was created, but they do know that it’s origin dates back more than 1.5 billion years.
Clues to the age of the Grand Canyon lie in the colorful layers of rock. Vishnu Schist is one type of black rock in the Grand Canyon and is the oldest. Volcanic ash, mud and sand washed down from mountains in ancient times, eventually developing into these rocks. Additional sedimentary rock was formed in the hundreds of millions of years after the oldest rock was laid. Oceans, deserts and swamps came into being and then disappeared, leaving their own deposits, resulting in a giant plateau, some of which we can see today. The youngest layer of rock was deposited 250 million years ago. This rock, called Kaibab limestone, is light in color.
After all the layers of rocks were formed, the Colorado River then started to carve through the rock plateau developing a canyon. The tributaries helped the River to erode additional rocks, making the Grand Canyon what it is today.
The Grand Canyon exists because of erosion. The Colorado River weaved its way over top of the rock plateaus causing a massive canyon in the rock plateau that spans up to 18 miles from one rim to the next. The Colorado River is still eroding the rocks to this day creating a beautiful work of art in the Earth.
Scientists don’t have all the details as to how the Grand Canyon was created, but they do know that it’s origin dates back more than 1.5 billion years.
Clues to the age of the Grand Canyon lie in the colorful layers of rock. Vishnu Schist is one type of black rock in the Grand Canyon and is the oldest. Volcanic ash, mud and sand washed down from mountains in ancient times, eventually developing into these rocks. Additional sedimentary rock was formed in the hundreds of millions of years after the oldest rock was laid. Oceans, deserts and swamps came into being and then disappeared, leaving their own deposits, resulting in a giant plateau, some of which we can see today. The youngest layer of rock was deposited 250 million years ago. This rock, called Kaibab limestone, is light in color.
After all the layers of rocks were formed, the Colorado River then started to carve through the rock plateau developing a canyon. The tributaries helped the River to erode additional rocks, making the Grand Canyon what it is today.
The Grand Canyon exists because of erosion. The Colorado River weaved its way over top of the rock plateaus causing a massive canyon in the rock plateau that spans up to 18 miles from one rim to the next. The Colorado River is still eroding the rocks to this day creating a beautiful work of art in the Earth.
Sample Outline:
Main Idea: Grand Canyon was a rock plateau until water cut into layers of rock creating a large canyon
- Detail 1: Layers of rock were deposited in the area over time creating an enormous rock plateau.
- Detail 2: The age of the Grand Canyon is known by analyzing the rock layers and how they were deposited.
- Detail 3: The Colorado River is still eroding the canyon to this day.