When people think of fossils, most people think of dinosaur fossils or a leaf
imprinted into a cement path walking out of school. But there are many
types of fossils. These types are molds, casts, trace fossils, and petrified
fossils. A mold is an imprint of anything in a rock, or any surface. It is like
the leaf that you see imprinted in the cement on your way out of school. A
cast is when there is a replica of that mold that is 3D, and has most of the
features. Trace fossils are basically what they say, fossils showing the
traces of anything, like a footprint. When that is preserved in the ground, it
is a trace fossil. A petrified fossil is when some or all of a fossil is replaced
with a mineral. Sometimes, when you go to a museum, and you see some
discoloration in a fossil, that is a petrified fossil. A regular fossil is the
fossil that you see in a museum with no discoloration at all.
CASTS AND MOLDS
Casts and molds normally form together. The mold is imprinted when the
cast, which is 3D, pushes into a rock, forming a mold. They are typically
formed in plain rock. Casts are rare on the surface, because pressure has
to push it down, so they normally form underground. The main rock you
will find a mold on is a soft rock, because then there doesn’t have to be a
ton of pressure to imprint the image.
Trace fossils aren’t rare. Most people have seen a trace fossil in their lives.
They are commonly found in muddy areas. When you step mud, and you
get mud all over your shoe, you may not realize it, but you made a trace
fossil. The most common trace fossils are dinosaur trace fossils because
they were heavy enough to imprint the ground and have had time to
preserve the traces.
A petrified fossil is very hard to find, but they are more common than
regular fossils. Petrified fossils are normally found deep underground,
where the minerals are. Fossils are fragile to chemical reactions, so the
chemical reactions can cause some of the minerals to form inside of the
fossil. Also, if the fossil is made inside a vain of anything, there is a good
chance that the fossil will be a petrified fossil
What are the four types of fossils?
Mold, cast, petrified, and trace
What is a mold?
A mold is an imprint of a fossil in a rock
Where do petrified fossils normally form?
Underground, near minerals
What is the most common trace fossil?
A dinosaur footprint