Rocks, Rossils, etc,..

• the method used by geologists to match rock layers of the same age.
• Matching is based on similarities in the sequencing of layers or unique common fossil species or groups of fossils.

convection currents

slower

4.6 billion yr old

1000 million

Any evidence of past life, ice age, or older.

(10,000 BC)

actual remains, may or may not be changed

usually bones, teeth, or shells, rarely is it soft fleshy parts of the organism

tracks, traits, burrows (called trace fossils)

coprolite ( fossil dung )

rapid burial

presence of hard parts (bone, teeth, shell)

• Replacement
• Carbonization
• Imprints

original materials are broken down and is replaced by minerals from groundwater occurs at a molecular level.

original bone/shell is turned to stone.

How?

The original material is dissolved away by ground water and minerals from the surrounding rock take its place.

Common replacement minerals: quartz, calcite, rarely hematite.

- all volatile (blood, fat, etc,..) (REACTIVE)

- all volatile ( reactive substances, liquids) are squeezed out leaving a thin film of carbon. Commonly preserves plants, fish, rarely others (salamanders, Jellyfish)

-all fluids (water based, also fats, blood) are squeezed out leaving a thin film of carbon. Commonly preserves leaves, fish, rarely frogs, salamanders, jellyfish.

thin bodied organisms with chitonous (scales,exterior) exoskeletons

- a three-dimensional replica of the organism (usually bone/shell)

- may be internal (from the inside of a shell, hardened mud) or external

surrounds the clasts (like a cake mold)

• - amber: fossilized tree sap
• - ice: only Ice Age organisms
• - tar: whole community preserved

the age of a fossil rock layer or igneous rock (intrusion/lava flow) in yrs.

...break down at a known rate into stable elements (daughter elements) called half lifes

the amount of time it takes for 50% of a radioactive element to break down into a stable element (daughter element)

any layer cut by a fault or intrusions older than the fault or intrusion

gap in the rock record stripped away by erosion

unequal

......major events and/or major changes in life forms units from largest to smallest

Eon -> Era -> Period -> Epoch

4.6 bya

3.8 bya

2.5 bya

Photosyntheis = first life

first single celled organisms

570 mya- now

• visible life
• simple multicellular fossils

Proterozoic Eon- origin of Earth

4.6 -2.5 bya?

Cenozoic/Mesozoic/Paleozoic Eras

570 mya- now

• "ancient life"
• Age of Invertabrates

570 mya

• "Middle Life"
• Age of Reptiles
• Dinos are dominant

225 mya

• Recent Life
• age of mammals

66.4 mya- now

• Precambrian Time: Origin of Earth
• Proterozoic Eon
• Phanerozoic Eon: Paleozoic Era
• Mesozoic Era
• Cenozoic Era

used for determining the age of rock layers

****must be common widespread geography exist for a limited time period****

life; living things