Fossils: are the remains of animals, plants or humans found in sediments and rocks.

e.g. bones, shell, leaves, carapace.

Fossilization: transformation of a living organism

into a fossil. This is a very long

process.

• The process of fossilization:– The animal, plant or human dies– Soft tissues (muscles and organs) are eaten

or decomposed– The hard parts (skeleton) are covered with

sediment– Over years, the sediments harden into rocks.– The fossils are found by scientists…or you!

• Fossilization of a dinosaur:

• What do fossils teach us?– A) the different forms of life that have existed

on Earth.– B) the changes that have marked Earth’s

history• Tectonic plates have changed Earth’s appearance

and that is why similar fossils are found on different continents far away from each other.

• Stratigraphy: sediments deposited on ocean floor, form rocks over time and are usually arranged in layers.

• Every stratigraphic layer is composed of sedimentary deposits of the same color, size and type of rock.

• The oldest layer is always on the bottom with the youngest layer on the very top. This is the principle of superposition.– E.g. old vs. new newspaper in the recycling

bin.

• Dating fossils:– There are two methods of dating fossils

• Relative dating: determining the age of fossils and rocks by examining their location in the superpositioned layers.

• Absolute dating: determining the age of fossils and rocks by measuring the quantity of certain radioactive elements (uranium and carbon 14) in the specimen.

• Index fossils: are fossils that help scientists find the approximate age of layered sediments.

• E.g. Scientists know the age of ammonites, a marine animal. When ammonites are found in rock layers, scientists know that the rock is approximately 110 Ma because that is the age of the ammonite found within.