Native voices share their personal and cultural connections to the Little Colorado River, from its headwaters to the Grand Canyon. Sign Up. Toggle Navigation Menu. Blog Hikes Newsroom Resources.
Act Donate Renew. Back to All Blog Posts. Ed Moss. What are the Grand Canyon rock layers? Need an acronym to remember the process? How old is the Grand Canyon? Curious about wildlife in Grand Canyon? Though some national parks and monuments are open, tribal lands on the Colorado Plateau are still largely closed to visitors. The Colorado Plateau's magnificent lands will be here waiting for you. Grand Canyon Blog. Lifeways of the Little Colorado River. Share This. Comments 3 Laura Crossey says:.
Great job! Loved your synopsis! Laura crossey says:. Have you seen this new report? Hi Laura, Thanks for reading and for sharing this report! There's certainly more we could have covered in this blog. Maybe next time we'll delve into those mysterious unconformities For many years, the canyon was thought to be five to six million years old — very young in geologic time.
This is still thought to be the case for at least part of the canyon. However, papers published throughout the years argue for a greater age of the canyon, ranging from 17 million years old to nearly 70 million years old Karlstrom, K. The Grand Canyon was originally thought to be carved by concurrent river erosion and tectonic uplift.
Two hypotheses abounded: one, that the river cut through sedimentary layers as the Colorado Plateau uplifted, and two, that the river began after uplift and was attempting to reach isostatic equilibrium. However, over the past several years, new hypotheses have been created. The current thinking is that the Grand Canyon is the result of several smaller, much older canyons and their respective rivers being pulled together as a result of stream capture and knickpoint migration along faults.
Some of these older canyons are up to 70 million years old, whereas other portions of the canyon are much younger, leading to current age debates Karlstrom, et. Stratigraphic Column.
The Grand Canyon is considered one of the best geologic exposures of the Paleozoic to Pre-Cambrian periods about ma to about million years ago; Mathis and Bowman, in the world. It has reached the Vishnu Schist and the Zoroaster Granite both Pre-Cambrian in age; approximately ma; Mathis and Bowman, at the bottom of the stratigraphic column. The geologic time scale of the Grand Canyon, as well as the geologic setting.
Borrowed from Mahis and Bowman, Shallow marine shelf deposit. Fossiliferous brachiopods, gastropods, crinoids, bryozoans. Represents the time of maximum eastward transgression of the Kaibab Sea Condon, Fossiliferous in nature, with brachiopods, gastropods, crinoids , and bryozoans present. Approximately ft thick. Contains of the most diverse rock varieties in the Canyon, i. Originally deposited near the shore of a shallow sea in mudflats and evaporate deposits. Very large scale cross-stratified sandstone.
Deposited by aeolian processes and consists of fine, well-sorted quartz grains Mckee, and Thickness varies from 57ft to over ft Middleton et. Present are fossilized trackways and tail-drag marks of prehistoric reptiles. Fossil trackway in Coconino Sandstone.
Photo credit Mikaela Reisman. Comparatively nonresistant unit of siltstone, mudstone, and sandstone. Thickness varies between ft to ft. Low angle cross-bedding present, as well as poorly-preserved plant fossils Blakey, Multiple, ill-preserved plant fossils present.
Supai Group ma Created from oceanic transgressions and regressions, forming alternating conglomerates, siltstones, and sandstones Blakey, Fossil examples of amphibians, reptiles, and terrestrial and marine plants present. Deposited atop the horizontal Redwall Limestone. Environments during deposition were most likely a moist and humid with orangey soil similar to soil found in the tropics today. Multimedia Gallery. Park Passes. Technical Announcements. Employees in the News.
Emergency Management. Survey Manual. The beginning of the story starts at the bottom of the canyon and moves forward in time as you get closer to the rim. Stratigraphy is the study of the rock layering, and reveals a wealth of information about what Earth was like when each layer formed.
In the Grand Canyon, there are clear horizontal layers of different rocks that provide information about where, when, and how they were deposited, long before the canyon was even carved. The Law of Superposition states that sediment is deposited in layers in a sequence, the oldest rocks are on the bottom and the youngest rocks are on the top, similar to the way that sand piles up in an hour glass. This principle is a key part of determining the relative age of a rock layer.
The three main rock layer sets in the Grand Canyon are grouped based on position and common composition and 1 Metamorphic basement rocks, 2 The Precambrian Grand Canyon Supergroup, and 3 Paleozoic strata. These three main sets of rocks were first described by the explorer and scientist John Wesley Powell during his expeditions of the Grand Canyon in the late s and early s.
Unconformities are gaps in the geologic record that occur when rocks or sediments are eroded away and time elapses before new deposition occurs. New sediment eventually forms new rock layers on top of the eroded surface, but there is a period of geologic time that is not represented. Types of Rock. The three main types of rock are igneous, sedimentary and metamorphic. Igneous rocks are cooled magma melted rock found underground or lava molten rock found above ground.
Granite cooled from magma, known as an intrusive igneous rock and basalt cooled from lava, known as an extrusive igneous rock are two types of igneous rocks. Sedimentary rocks are formed by smaller pieces of sand and mud stick together in layers. Examples include: sandstone, mudstone ,shale , siltsone, chert, limestone, and more. Sedimentary rocks often contain fossils that can be used to help identify the age of the rock. Certain fossils, called index fossils, are particularly useful because they are abundant in a relatively narrow time range.
Over time, pressure increases as sediment increases, and minerals help form these rock layers. All three rock types can be found in the Grand Canyon, and each layer adds an important understanding to the geologic history of the region.
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