Fossils

What is a FOSSIL?

• Fossil = The preserved remains or traces of an organism that lived in the past.

• Fossils give clues to:– diversity of living things over history of Earth.– past climate and surface changes on Earth.– changes that have occurred to organisms over

time.

Types of Fossils

• There are different types of fossils based on how they were formed.

• The environment they form in also cause them to form different types of fossils.

Types:•Mold•Cast•Petrified•Preserved•Carbonized•Trace

Mold Fossil• Forms when sediments bury an organism and

the sediments change to rock.• The organism decays, leaving a cavity in the

shape of the organism.

Cast Fossil• Forms when a mold is filled with sand or mud

that hardens into the shape of the organism.

Petrified Fossil• AKA “Permineralized Fossil”• Forms when minerals soak into buried

remains.• The minerals replace the remains, changing

them to rock.

Preserved Fossil• Forms when entire organism (or parts of it)

are prevented from decaying by being trapped in rock, ice, tar, or amber.

Carbonized Fossil• Forms when organisms or parts (like leaves, stems, flowers,

fish) are pressed between layers of soft mud or clay.• The mud or clay hardens, squeezing almost all of the

decaying organism away.• This leaves the carbon imprint in the rock.

Trace Fossil• Forms when mud or sand hardens to stone

where a footprint, trail, or burrow of an organism was left behind.

Fossil Record• Millions of fossils have been collected and

studied.• The Fossil Record:– gives important info about past life and environments

on Earth.– Shows extinction of life forms– Shows when new life forms appear

• Certain fossilized organisms could only live in specific environments under particular climate conditions.