The Grand Canyon is in northern Arizona. It was carved by the Colorado River as the land rose. The knife and cake analogy is used. The river is a knife held stationary while the cake is lifted. It took 10 million years to carve the Canyon.
The Grand Canyon is 277 miles long and a mile deep. It averages 10 miles across. It is shaped like a woman's bosom. The Canyon continues to widen as its rims disintegrate. 2 billion years are exposed.
Erosion from wind, water & ice widen the Canyon. Water gets into the cracks in rocks and freezes. The cracks widen, and the Canyon 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 appear as we dig deeper.
Sedimentary rocks were laid down by water. Layers formed as water moved in and out. Limestone formed when water moved in. Shale formed when it moved out.
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 the era of invertebrates.
Schist is metamorphic rock. The schist at the bottom of the Canyon is 2 billion years old.
Coconino Sandstone is what remains of sand dunes. Solidified sand has no fossils.
Hermit shale is solidified mud. It contains plant fossils, showing it was above water.
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.
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.