化石的种类 (Types of Fossils)
Petrified Fossils (Mineralization) (石化化石)
•The word “petrified” means “turning into stone.”
•Petrified fossils form when minerals replace all or part of an organism.
•Water is full of dissolved minerals. It seeps through the layers of sediment to reach the dead organism. When the water evaporates, only the hardened minerals are left behind.
•The word “petrified” means “turning into stone.”
•Petrified fossils form when minerals replace all or part of an organism.
•Water is full of dissolved minerals. It seeps through the layers of sediment to reach the dead organism. When the water evaporates, only the hardened minerals are left behind.
Mold and Cast (铸模和铸型化石)
•A mold forms when hard parts of an organism are buried in sediment, such as sand, silt, or clay.
•The hard parts completely dissolve over time, leaving behind a hollow area with the organism’s shape.
•A mold forms when hard parts of an organism are buried in sediment, such as sand, silt, or clay.
•The hard parts completely dissolve over time, leaving behind a hollow area with the organism’s shape.
•A cast forms as the result of a mold.
•Water with dissolved minerals and sediment fills the mold’s empty spaces.
•Minerals and sediment that are left in the mold make a cast.
•A cast is the opposite of its mold.
•Water with dissolved minerals and sediment fills the mold’s empty spaces.
•Minerals and sediment that are left in the mold make a cast.
•A cast is the opposite of its mold.
Carbon Films (碳片儿)
•All living things contain an element called carbon. •When an organism dies and is buried in sediment, the materials that make up the organism break down. •Eventually, only carbon remains. •The thin layer of carbon left behind can show an organism’s delicate parts, like leaves on a plant.
•All living things contain an element called carbon. •When an organism dies and is buried in sediment, the materials that make up the organism break down. •Eventually, only carbon remains. •The thin layer of carbon left behind can show an organism’s delicate parts, like leaves on a plant.
Trace Fossils (踪迹化石)
•Trace fossils show the activities of organisms.
•An animal makes a footprint when it steps in sand or mud.
•Over time the footprint is buried in layers of sediment. Then, the sediment becomes solid rock.
•Trace fossils show the activities of organisms.
•An animal makes a footprint when it steps in sand or mud.
•Over time the footprint is buried in layers of sediment. Then, the sediment becomes solid rock.
Preserved Remains (保存下来的遗体 bǎocún xiàlái de yítǐ)
Some organisms get preserved in or close to their original states. Here are some ways that can happen.
Amber (琥珀)
An organism, such as an insect, is trapped in a tree’s sticky resin and dies. More resin covers it, sealing the insect inside. It hardens into amber.
An organism, such as an insect, is trapped in a tree’s sticky resin and dies. More resin covers it, sealing the insect inside. It hardens into amber.
Tar (焦油)
An organism, such as a mammoth, is trapped in a tar pit and dies. The tar soaks into its bones and stops the bones from decaying.
An organism, such as a mammoth, is trapped in a tar pit and dies. The tar soaks into its bones and stops the bones from decaying.
Ice (冰)
An organism, such as a woolly mammoth, dies in a very cold region. Its body is frozen in ice, which preserves the organism—even its hair!
An organism, such as a woolly mammoth, dies in a very cold region. Its body is frozen in ice, which preserves the organism—even its hair!