Geologic Timeline and Processes

The formation of the Grand Canyon began over 1.8 billion years ago, and it continues to develop as the years go on. Throughout the long timeline, you can see the different weathering effects on this national park and the unique parts created from it. There are towering cliffs, colorful rock layers, and incredible views.

In this section we will go over a couple of the main events that shaped the canyon into what it is today.

General Geologic Overview:

1.8 billion years: Vishnu Basement Rocks are formed.

1.2 billion years: Unkar group and the Bass Formation were deposited.

740 millions years: Bright Angel Shale and Tapeats Sandstone formed.

550 million years: Muav Limestone and Temple Butte Formation deposited.

525 million years: Redwall Limestone formed.

505 million years: Surprise Canyon formed, and Hakatai Shale was deposited.

270 million years: Kaibab Limestone formed.

About 70-55 million years: Laramide Orogeny.

About 6 million years: Colorado River began carving the Grand Canyon.

Metamorphism and Magmatism

Metamorphism and magmatism played crucial roles in shaping the geological landscape of the Grand Canyon, although their direct influence on its formation is relatively minor compared to other processes like erosion and tectonic activity.

Vishnu Basement Rocks

1.8 Billion Years

The Vishnu Basement Rocks are a mix of metamorphic and igneous rocks with vertical folds and foliation. This contains all of the ancient rocks at the bottom of the Grand Canyon. Metamorphism and Magmatism were main contributing factors in the formation of these ancient rock layers. Due to intense heat and pressure over time, metamorphic rocks were formed. These rocks were later intruded by igneous rock, giving them their unique characteristics.

The Great Unconformity

The Great Unconformity represents ~1.2 billion years of missing rock record, either due to erosion or non-deposition. The Great Unconformity exposed in the Grand Canyon separates the Tapeats Sandstone from ancient Proterozoic rocks.

The Great Unconformity above the Granite Gorge has Vishnu Basement Rocks below the white line and the Layered Paleozoic Rocks above it. At this location, there are 1.2 billion years missing (not recorded) across this contact.

Deposition

Deposition, which refers to the process by which sediments, soil, and rocks are added to a landform or landmass, played a key element in forming many of the geological features we see in the Grand Canyon today.

Unkar Group & Base Formation

1.2 Billion Years

The Unkar Group is the oldest section of the Grand Canyon Supergroup. The oldest formation of this super group is the Bass Formation. These were created through Deposition of different sediments. This contains sedimentary rocks such as sandstone, shale, and limestone. Volcanic eruptions also added to the layers of this section of the Grand Canyon.

Bright Angel Shale & Tapeats Sandstone

740 Million Years

The Bright Angel Shale is mostly a sediment covered slope/platform with low sandstone ledges. There is a mineral in it called glauconitic, that makes the layer the green color you see.

The tapeats sandstone were formed through deposition of sand and other sediments in a marine environment.

Muav Limestone & Temple Butte Formation

550 Million Years

The layers of the muav limestone are a result of marine sediments settling over millions of years. What was once deposited in shallow sea, eventually hardened into rock creating the layers we see today.

As for the temple butte formation, we see a result of sediments being deposited and erosion. Layers of various materials gathered and hardened over time, before being carved out by the colorado river. This is what gave the temple butte its shape.

Redwall Limestone Formed

Photo By: Kristen Caldon

525 Million Years

Again, through sedimentation the redwall limestone was formed. The red color that is seen is a result of iron oxide minerals present in the rock. Throughout the millions of years of formation, minerals were compacted and hardened into the limestone we see today.

Surprise Canyon Formation &

Hakatai Shale

505 Million Years

Surprise canyon is made up of various materials like limestone, sandstone, and shale. Through the carving of the colorado river, rock layers were exposed and gave us the canyons we see today.

The Hakatai Shale is known for its dark gray and fine-grained texture.

Kaibab Limestone Formed

270 Million Years

The Kaibab limestone is a prominent formation in the Grand Canyon. This is the light-colored, thick layer of sedimentary rock found at the top of the canyon. Since the limestone is thick, it has been able to resist erosion leaving this national park with the steep cliffs you see.

The Laramide Orogeny was caused by subduction of a plate at a shallow angle.

Laramide Orogeny

Roughly 75 - 55 million years ago

The Laramide Orogeny was a time period of mountain building in western North America. During this time subduction occurred in a faster, shallower angle. This unique angle allowed for deformation to move further inward from the plate margin, bringing about the uplift of the rocky mountains as well as the Colorado Plateau. The Laramide Orogeny set the stage for the formation of the Grand Canyon by uplifting vast regions of the southwestern United States, creating high plateaus, and initiating the incision of deep river canyons.

Colorado River

Roughly 6 million years

Much of the Grand Canyon as we see it today has been formed due to downcutting and erosion. This relentless downcutting and erosion by the Colorado River over millions of years have sculpted the intricate landscape of the Grand Canyon, creating its iconic cliffs, terraces, and rock formations. This ongoing process continues to shape the canyon, albeit at a much slower pace than in the past, demonstrating the dynamic interplay between geological forces and erosional processes.

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