A Travellerspoint blog



The Grand Canyon is in northern Arizona. It was carved by the Colorado River as the land rose. A cake and knife analogy is used. The river is a knife held stationary as the cake is uplifted. The Canyon took 7 million years to carve.

The Grand Canyon is 277 miles long and a mile deep, averaging 10 miles across. It is shaped like a bra or a woman's bosom. Two billion years of Earth's history are exposed. The Canyon continues to widen as the rims disintegrate.

Erosion by water, ice, wind and the course of the Colorado widen the Canyon. Water has the most impact. It gets into cracks between rocks and freezes. The cracks widen, and Canyon walls collapse.

Geologists study rocks. Paleontologists study fossils. Their work overlaps because fossils are found in rocks, a sign that they are the same age.

Rocks can be dated. Even if they could not, it is obvious from the fossil record as we dig deeper into the earth that life was simpler in the past. Only a dogmatist could deny evolution.

Sedimentary rocks were laid down by water. Less complex fossils are found in the different layers as we descend.

Layers of sedimentary rock form when oceans move in and out. Limestone forms when oceans move in. Shale forms when they move out.

Rocks in the Grand Canyon are from the Paleozoic Era. There are no rocks from the Mesozoic or Cenozoic. They either eroded away or were never laid down. That means there are no fossils of birds, reptiles or mammals. No dinosaurs. The Paleozoic is the era of shelled invertebrates. Trilobites flourished in Cambrian oceans.

Kaibab Limstone is the top layer at the Canyon. It is 250 million years old. It formed at the bottom of an ocean and contains fossils of marine animals.

Coconino Sandstone is the remnant of sand dunes from 270 million years ago. It contains no fossils. Sandstone is solidified sand.

Hermit shale was deposited 280 million years ago. It contains plant fossils, indicating that it was above water. Shale is solidified mud.

Vishnu Schist at the bottom is 2 billion years old. Schist is metamorphic rock.

Geologic time:
CENOZOIC ERA - Mammals - Present-60 million years ago
MESOZOIC ERA - Reptiles - 60 million-220 million
PALEOZOIC ERA - Inverebrates - 220 million-540 million

Permian - 220 million years ago
Pennylvanian - Carboniferous 325 million
Mississippian - Carboniferous 360 million
Devonian - 410 million
Silurian - 440 million
Ordovician - 500 million
Cambrian - 540 million
Precambian Era - Bottom of the Grand Canyon. The oldest fossils are 3 billion year old microbes. The oldest rocks are 3.8 billion. The age of the earth is 4.6 billion.

The Grand Canyon offers the most complete geologic column on the planet. Rock layers are the same on both the north and south rims.


Posted by Jim Colyer 21:11 Comments (0)

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