Fossils

The remains or evidence of a

living thing

Fossils: Remains, Imprints, Traces, or Evidence of Once Living Organisms.

Tells us what , where, when, how organisms lived.

Tells us the history of life on earth. Tells us about climates and environments of

the past.

Conditions Necessary to Create Fossils.

Organism quickly buried to avoid decay. Hard parts which are less likely to decay. Usually occur in Sedimentary rock.

Types of FossilsCarbonaceous Films

Mold & Cast

Trace Fossils

Petrified Remains

Original Remains

Carbonaceous Films

Like a picture of the organism. Thin layer of carbon often left behind forming

image.

Mold and Cast

Buried hard parts in rock dissolve or decay leaving a MOLD (empty space in rock).

Mold later fills with sediments that harden forming a CAST (filled in mold).

Trace Fossil

Evidence of animal activity.– Examples:

Footprints Worm holes Burrows

Trace Fossils

Marks or evidence of animals but show no part of the animal

Ex: footprints, droppings, burrows

Petrified Remains

Hard and rock like Original material

replaced by minerals Water flows through

removing material and carrying minerals that crystallize in their place

Most bones found are petrified.

Original Remains

Actual parts of organism found

– Examples: Insect in amber Animal frozen Animal trapped in

tar

Preservation

Freezing Amber: when sap

fossilizes with trapped organisms

Tar Pits: trap animals and preserve them

Fossil Interpretation

Fossils are arranged according to age, so they show a progression of development

Fossils indicate past surface conditions Fossils give evidence of past climates Fossils tell appearance and activity of plants

and animals

Index Fossils

From species that– Existed for a short period of time– Were abundant– Were wide spread

Used to determine the age of rock layers that contain them.– Rock layers that contain the same index fossil are

thought to be about the same age.

Fossils – Dun, Dun, Dun!