What Are Fossils? – Continued
Written for the KidsKnowIt Network by: Brandon Guymon
There are many other types of fossils. Compression fossils form when leaves become trapped between layers of sediment (mud, fine sand, or volcanic ash) and get smashed flat. Over time the sediment hardens into rock and the leaves become fossils. This usually happens with leaves because they are already flat.
Trace fossils are the remains of trackways, burrows, eggs, nests, and fossil coprolites (poop). Trace fossils can tell us a lot about the animals that left them. For example, from trackways we can tell about how fast an animal was moving when they made the tracks. From coprolites we can tell what kind of things an animal ate. Trace fossils are important because they tell us how an animal lived, and what it was like in their environment.
Anyone can find fossils. I have been finding fossils for nearly as long as I can remember, and finding fossils is still one of my favorite things to do. I found many fossils as a small child near my grandmother’s house in Huntington, Utah. Huntington, Utah, is near the famous Cleveland Lloyd Dinosaur Quarry and is surrounded by the Morrison Rock Formation. The Morrison Rock Formation is famous worldwide for having dinosaur fossils in it. Near the home where I grew up I could find Trilobites and the trace fossils made by ancient worms as they burrowed though soft mud at the bottom of an ancient sea.
Fossils are found in sedimentary rocks. Sedimantary rocks are one of the three main types of rock. The other two are igneous and metamorphic rocks. Sedimentary rocks are formed when other types of rocks are eroded away. Broken down bits of rock, called sediments, pile up in what geologists call beds or layers. Over time sediments get buried by new layers of sediments. Sometimes these sediments harden into rock. These rocks are now sedimentary rocks. Of the three different rock types only sedimentary rocks can hold fossils. Igneous rocks are formed when liquid melted (magma or lava) rock cools and hardens. Metamorphic rocks are formed under intense heat and pressure. Metamorphic rocks can be formed out of either sedimentary or igneous rock; however, the process of forming metamorphic rock would mess up or destroy any fossils that happened to be in the rock.
If you want to find fossils you will need to find the right kind of sedimentary rocks. While digging on the beach in England in 2010, 5-year-old Emily Baldry discovered the fossil of a 160 million year old sea creature. Sedimentary rocks typically do not live in your backyard, so please don’t go digging, unless you have your parents’ permission. When you are outside where the rocks “live,” keep your eyes open, you just might find a fossil. Even if you don’t find a fossil, rocks are just plain cool.
Emily Baldry with the toy shovel she was using when she found her fossil. When the fossil was first dug up, it looked like a large clump of hard mud. A fossil expert removed the hardened mud to reveal the fossil pictured above.