Fossils

Fossils usually form when sediment buries a dead organism. As sediment piles up, the organism's remains are subjected to pressure and heat. These conditions force gases and liquids from the body. A thin film of carbon residue is left, forming a silhouette of the original organism called a carbon film.

Fossils form through the process of mineral replacement beginning when an organism dies and is buried. Groundwater seeps around the organism, and the minerals in the water gradually replace the minerals in the hard parts of the organism.

Not all rocks contain fossils. Whether or not a dead organism becomes a fossil depends upon how well it's protected from scavengers and agents of physical destruction. however, quick burial isn't always enough to make a fossil. organisms have a better chance of becoming fossils. If they have hard parts such as bones, shells, or teeth. hard parts decay more slowly.

Scientists can use fossils to learn about past environments. By studying to the fossilized remains of ancient organisms, scientists can infer what type of climate they lived in by comparing them to similar organisms alive today.

Jellyfish are invertebrates, so they do not have the hard body parts that favor fossilization.

Trace fossils are not the preserved remains of ancient organisms. Instead, they provide information about the activities of the organisms. Examples are fossilized footprints and burrows.

Fossil correlation uses the principle that rock strata containing fossils of the same age must be the same age as the fossils. Geologists can compare the known lifespan of the fossilized plant or animal to postulate the age of the rock layers.

C

Millions of years ago, swamps covered much of Earth. Layers of dead, decaying swamp plants formed a soft material called peat. Over time, layers of rock formed over the peat. Slowly, the peat changed into coal.

A mold is a hollow rock left by an organism, A cast is when the rock is filled with sediment. They both are usually found in creeks, rivers, and streams. A mold is a negative imprint, While a cast preserves the external form of the organism.

B. 1.8 million years.

True

carbonaceous film

Remains

hard

False

casts

mold

True

molds

True

fossil

widespread geographically

D

trace