Welcome to Bright Angel Point,
from here you can capture the essence of Grand Canyon
geology. The Grand Canyon is extensive--approximately
277 miles long, incredibly deep--over one mile, and here the north and south
rim are approximately 10 miles apart. As you gaze out into the Grand Canyon you are looking at one of nature’s
geological wonders. Here you can see what
a symphony of stone, time, and water can compose.
One of the first key components that make the Grand Canyon grand starts with depositing of sediment. Each
and every layer in the canyon represents a type of depositional environment
that once existed in the region. There are three types of rock found in the
world; sedimentary, metamorphic, and igneous--and all three types are below
your feet. Each rock layer tells a story
that starts with the older igneous and metamorphic rocks on the bottom and the
more colorful sedimentary rock layers stacked on top.
As you glance down into the inner canyon you are looking at
the Precambrian Schist formation; geologists date this formation to around 1700
million years old. During this time Arizona
actually had ocean front property, since the North American Plate was colliding
with a chain of volcanic islands that created a mountain range. The mountains
would ultimately erode away leaving only the basement rocks, which you see
today. As you peer down at these rocks you are looking at almost half of the
Earth’s history.
As your eyes travel up the South Rim, notice the red sheer
cliff rock layer—this 500-foot cliff layer is prominent throughout the canyon
due to its red-stained face. Around 340 million years ago marine waters covered
large portions of the North American continent.
The Redwall Limestone would be deposited in this shallow sea
environment. The red you see is not the limestone’s true color. Over time the
soft shale sloped layer above, which is enriched with iron, has leached upon
the grayish limestone creating the famous Redwall.
High above the Redwall is the prominent white cliff called
the Coconino Sandstone. The ocean receded 270 million years ago, leaving behind
a harsh desert climate similar to the Sahara Desert.
This white cliff is perhaps the most evident layer throughout the Grand Canyon.
The ocean would eventually rise again covering the edge of
the continent creating a new limestone layer called the Kaibab, coined from the
Paiute Band term meaning “mountain lying down.” This would be the layer your
feet are now resting on. On your hike back, look around to see if you spot any
of the ancient sea life fossils which were past residents of the Grand Canyon area.
At this time you would be viewing an ocean rather than a
canyon, since the rocks were at sea level, unlike today. Over 30 million years, these rocks would be
pushed more than a mile up, exposing them to powerful forces of erosion. This gentle uplift was caused by the
collision of tectonic plates, since continents have been migrating across the
earth’s surface for billions of years. Millions of years later the North Rim would be tilted an additional 1600 feet higher
than the South Rim. Long after uplift, the snow-fed Colorado
River would finally find its way to the sea, carving its way
through soft sedimentary rock. The river now flows across the crystalline core
of the continent. While the river carved the canyon, the semi-arid climate
makes it possible for rock to be preserved, as well as seen. The Grand Canyon is one of many geological paradises in the
world. It just so happens that this canyon allows us to gaze through its window
of time.