The Grand Canyon is in northern Arizona. It was carved by the Colorado River. It is 10 million years old..
The Canyon is 277 miles long and a mile deep. It averages 10 miles across. It continues to widen as its rims disintegrate. 2 billion years are exposed.
Erosion from wind, water & ice widen the Canyon. Water gets into cracks and freezes. The cracks widen, and the walls collapse. The Grand Canyon is the most complete geologic column on the planet. Rock layers at the North and South Rims are the same.
Geologists study rocks. Paleontologists study fossils. Their work overlaps because fossils are found in rocks, showing that they are the same age.
Rocks can be dated. Even if they could not, it is obvious that life was less complex in the past. Simpler fossils are found as we dig deeper.
Rocks in the Grand Canyon are from the Paleozoic Era. There are no rocks from the Cenozoic or Mesozoic. They were either eroded or never laid down. That means there are no fossils of mammals or dinosaurs. The Paleozoic was an era of invertebrates.
Sedimentary rocks are laid down by water. Layers form when water moves in and out. Limestone forms when water moves in. Shale forms when it moves out.
Kaibab Limestone is the top layer. It formed at the bottom of an ocean and has fossils of sea animals from 250 million years ago.
Hermit shale is solidified mud. It contains plant fossils, showing it was above water.
Coconino Sandstone is what remains of sand dunes. Solidified sand has no fossils.
Schist is metamorphic rock. The schist at the bottom of the Canyon is 2 billion years old.
The age of the earth is 4.6 billion years. The oldest rocks are 4 billion. The oldest fossils are 3.8 billion year old microbes.
1 Paleozoic Era - 540 million years ago to 245 million years ago - Invertebrates.
2 Mesozoic Era - 245 million years ago to 65 million years ago - Fish, amphibians, reptiles, dinosaurs & birds.
3 Cenozoic Era - 65 million years ago to the present - Mammals.