2020 / 1 / 22
Radioactive Dating Techniques
Corals
- daily growth rains in corals can be used to date
- there were 400 days in a year (440 million years ago)
Carbon 14
starts off as nitrogen-14 (in atmosphere)
large object from outer-space (cosmic ray)
hits nitrogen-14 and removes 2 protons
makes CO2
plant consumes CO2
animal eats plants
everybody is a little bit radioactive
we can tell how long a ago a plant or animal died by using the amount of radioactive material in a plant
Timeline
5 mass extenctiins
680 million years ago = first multicellular organisms (sponge)
590 million years ago = first animals with hard shells
520 million years ago = first fish
425 million years ago = first plants on land
360 million years ago = first land vertebrates
??? million years ago = first reptile
252 million years ago = permium period mass extinction
225 million years ago = first dineceor
215 million years ago = first mammal
180 million years ago = first bird
120 million years ago = first flower (angiosperms)
66 million years ago = mass extinction
50 million years ago = first modern day mammals
40 million years ago = first proto-humans
first homo-sapiens
Half Life
- time it takes for half of an isotope to decay