Backyard Dig By Katie, Lena, and Brooke

Description In the hole that we dug in our backyard, we found many layers of rock. At the bottom of the hole was a rock with a fossil of a stromatolite. We know that was the oldest rock and fossil because it was on the bottom. The oldest rock is on the bottom because of superposition; superposition is the order of the rocks and fossils from each era. That layer of rock is from the Precambrian Era, which literally means “before Cambrian.” The next rock layer we found was from the Paleozoic Era, which literally means “Ancient life.” We found a fossil of a trilobite in that layer of rock, and trilobites lived in the Paleozoic Era. The next rock layer we found was from the Mesozoic Era, which literally means “middle life.” We know it was from this Era because we found a fossil of a dinosaur in that layer, and dinosaurs thrived in that era. The top layer of rock we found was from the Cenozoic Era, which literally means “Recent life.” We know it was from that era because we found a fossil of a skull in the rock layer. We also know that this rock and fossil is the youngest because it was on the top. The difference between a cast and a mold is that a cast is 3D and you can actually see the shape of the object. In a mold, you can’t see the whole shape but it has the outline of the object. The fossils were never alive, but the image the fossil displays was once alive. We know this because bones and soft parts of bodies can’t survive for millions of years. We know that the history of our backyard is very old. We know this because each layer is from different eras, that date back to 4,600 million years ago during the Precambrian Era. In the hole that we dug in our backyard, we found many layers of rock. At the bottom of the hole was a rock with a fossil of a stromatolite. We know that was the oldest rock and fossil because it was on the bottom. The oldest rock is on the bottom because of superposition; superposition is the order of the rocks and fossils from each era. That layer of rock is from the Precambrian Era, which literally means “before Cambrian.” The next rock layer we found was from the Paleozoic Era, which literally means “Ancient life.” We found a fossil of a trilobite in that layer of rock, and trilobites lived in the Paleozoic Era. The next rock layer we found was from the Mesozoic Era, which literally means “middle life.” We know it was from this Era because we found a fossil of a dinosaur in that layer, and dinosaurs thrived in that era. The top layer of rock we found was from the Cenozoic Era, which literally means “Recent life.” We know it was from that era because we found a fossil of a skull in the rock layer. We also know that this rock and fossil is the youngest because it was on the top. The difference between a cast and a mold is that a cast is 3D and you can actually see the shape of the object. In a mold, you can’t see the whole shape but it has the outline of the object. The fossils were never alive, but the image the fossil displays was once alive. We know this because bones and soft parts of bodies can’t survive for millions of years. We know that the history of our backyard is very old. We know this because each layer is from different eras, that date back to 4,600 million years ago during the Precambrian Era.

Diagram of the Hole