Life

Uniformitarianism

geologic events and phenomena that occur today also happened in the past and will happen in the future.

Cast and mold fossils

* the impression made is called the mold
* when minerals /sediment fill it in, it is called a cast

Amber

the plant or animal is stuck in tree sap- over time the sap hardens into amber and is preserved

Radiometric dating

the method of finding the absolute age of rock based on comparing the amounts of stable and unstable particles.

Law of Superposition

states that in a sequence of undisturbed rocks, the oldest layers are at the BOTTOM and the youngest are at the TOP.

Geologic Time Scale

divides Earth’s history into intervals of time defined by major events or changes

**Fossilization**

remains of the dead organism were covered by sediment and preserved

Fossils

the remains of once-living organisms (plants /animals /bacteria /fungi)

Relative Age

relates to whether one layer is older than another.

Eon

hundreds of millions /billions of years.

in the Phanerozoic Eon

Era

tens of millions of years

in the Cenozoic Era

Period

millions of years

in the Quarternary Period

Epoch

tens of thousands of years

in the Holocene Epoch

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Age

hundreds to thousands of years 

in the Meghalayan Age

**permineralized fossil**

the bones or tree have become rock

**carbonized fossil**

only the carbon remains and leaves a film behind 

**frozen remains**

the whole organism is frozen including the organs

**tar pit fossil**

organism gets stuck in a sticky tar

the tar preserves the bones

**trace fossil**

a record of the activity of the animal

tracks, nests, burrows, scratch marks, etc.

**A person who studies fossils is a ……**

**Palaeontologist**

**A person who studies rocks, soils, and minerals is a …..**

**Geologist**

**Absolute Age**

actual age 

**Radioactive decay**

unstable particles in living things change into stable particles

**Half-life**

the amount of time needed for half of a sample of a radioactive substance to decay

Earth is

4,600,000,000 years old

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**Extinction**

when all the members of a species die out

**Fossil Record**

a collection of all known fossils and their placement in order from most recent

**Mass Extinction**

large numbers of species die out in different parts of Earth during a relatively short period of time

**REASONS FOR MASS EXTINCTION**

* Natural disasters
* Meteor strike
* Climate change
* Low oxygen levels in oceans
* Diseases
* Solar events